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Negative Emissions Technologies and Reliable Sequestration: A Research Agenda (2018)

Chapter: 4 Bioenergy with Carbon Capture and Sequestration

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Suggested Citation:"4 Bioenergy with Carbon Capture and Sequestration." National Academies of Sciences, Engineering, and Medicine. 2018. Negative Emissions Technologies and Reliable Sequestration: A Research Agenda. Washington, DC: The National Academies Press. doi: 10.17226/25259.
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Suggested Citation:"4 Bioenergy with Carbon Capture and Sequestration." National Academies of Sciences, Engineering, and Medicine. 2018. Negative Emissions Technologies and Reliable Sequestration: A Research Agenda. Washington, DC: The National Academies Press. doi: 10.17226/25259.
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Suggested Citation:"4 Bioenergy with Carbon Capture and Sequestration." National Academies of Sciences, Engineering, and Medicine. 2018. Negative Emissions Technologies and Reliable Sequestration: A Research Agenda. Washington, DC: The National Academies Press. doi: 10.17226/25259.
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Suggested Citation:"4 Bioenergy with Carbon Capture and Sequestration." National Academies of Sciences, Engineering, and Medicine. 2018. Negative Emissions Technologies and Reliable Sequestration: A Research Agenda. Washington, DC: The National Academies Press. doi: 10.17226/25259.
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Suggested Citation:"4 Bioenergy with Carbon Capture and Sequestration." National Academies of Sciences, Engineering, and Medicine. 2018. Negative Emissions Technologies and Reliable Sequestration: A Research Agenda. Washington, DC: The National Academies Press. doi: 10.17226/25259.
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Suggested Citation:"4 Bioenergy with Carbon Capture and Sequestration." National Academies of Sciences, Engineering, and Medicine. 2018. Negative Emissions Technologies and Reliable Sequestration: A Research Agenda. Washington, DC: The National Academies Press. doi: 10.17226/25259.
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Suggested Citation:"4 Bioenergy with Carbon Capture and Sequestration." National Academies of Sciences, Engineering, and Medicine. 2018. Negative Emissions Technologies and Reliable Sequestration: A Research Agenda. Washington, DC: The National Academies Press. doi: 10.17226/25259.
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Suggested Citation:"4 Bioenergy with Carbon Capture and Sequestration." National Academies of Sciences, Engineering, and Medicine. 2018. Negative Emissions Technologies and Reliable Sequestration: A Research Agenda. Washington, DC: The National Academies Press. doi: 10.17226/25259.
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Suggested Citation:"4 Bioenergy with Carbon Capture and Sequestration." National Academies of Sciences, Engineering, and Medicine. 2018. Negative Emissions Technologies and Reliable Sequestration: A Research Agenda. Washington, DC: The National Academies Press. doi: 10.17226/25259.
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Suggested Citation:"4 Bioenergy with Carbon Capture and Sequestration." National Academies of Sciences, Engineering, and Medicine. 2018. Negative Emissions Technologies and Reliable Sequestration: A Research Agenda. Washington, DC: The National Academies Press. doi: 10.17226/25259.
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Suggested Citation:"4 Bioenergy with Carbon Capture and Sequestration." National Academies of Sciences, Engineering, and Medicine. 2018. Negative Emissions Technologies and Reliable Sequestration: A Research Agenda. Washington, DC: The National Academies Press. doi: 10.17226/25259.
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Suggested Citation:"4 Bioenergy with Carbon Capture and Sequestration." National Academies of Sciences, Engineering, and Medicine. 2018. Negative Emissions Technologies and Reliable Sequestration: A Research Agenda. Washington, DC: The National Academies Press. doi: 10.17226/25259.
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Suggested Citation:"4 Bioenergy with Carbon Capture and Sequestration." National Academies of Sciences, Engineering, and Medicine. 2018. Negative Emissions Technologies and Reliable Sequestration: A Research Agenda. Washington, DC: The National Academies Press. doi: 10.17226/25259.
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Suggested Citation:"4 Bioenergy with Carbon Capture and Sequestration." National Academies of Sciences, Engineering, and Medicine. 2018. Negative Emissions Technologies and Reliable Sequestration: A Research Agenda. Washington, DC: The National Academies Press. doi: 10.17226/25259.
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Suggested Citation:"4 Bioenergy with Carbon Capture and Sequestration." National Academies of Sciences, Engineering, and Medicine. 2018. Negative Emissions Technologies and Reliable Sequestration: A Research Agenda. Washington, DC: The National Academies Press. doi: 10.17226/25259.
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Suggested Citation:"4 Bioenergy with Carbon Capture and Sequestration." National Academies of Sciences, Engineering, and Medicine. 2018. Negative Emissions Technologies and Reliable Sequestration: A Research Agenda. Washington, DC: The National Academies Press. doi: 10.17226/25259.
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Suggested Citation:"4 Bioenergy with Carbon Capture and Sequestration." National Academies of Sciences, Engineering, and Medicine. 2018. Negative Emissions Technologies and Reliable Sequestration: A Research Agenda. Washington, DC: The National Academies Press. doi: 10.17226/25259.
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Suggested Citation:"4 Bioenergy with Carbon Capture and Sequestration." National Academies of Sciences, Engineering, and Medicine. 2018. Negative Emissions Technologies and Reliable Sequestration: A Research Agenda. Washington, DC: The National Academies Press. doi: 10.17226/25259.
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Suggested Citation:"4 Bioenergy with Carbon Capture and Sequestration." National Academies of Sciences, Engineering, and Medicine. 2018. Negative Emissions Technologies and Reliable Sequestration: A Research Agenda. Washington, DC: The National Academies Press. doi: 10.17226/25259.
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Suggested Citation:"4 Bioenergy with Carbon Capture and Sequestration." National Academies of Sciences, Engineering, and Medicine. 2018. Negative Emissions Technologies and Reliable Sequestration: A Research Agenda. Washington, DC: The National Academies Press. doi: 10.17226/25259.
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Suggested Citation:"4 Bioenergy with Carbon Capture and Sequestration." National Academies of Sciences, Engineering, and Medicine. 2018. Negative Emissions Technologies and Reliable Sequestration: A Research Agenda. Washington, DC: The National Academies Press. doi: 10.17226/25259.
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Suggested Citation:"4 Bioenergy with Carbon Capture and Sequestration." National Academies of Sciences, Engineering, and Medicine. 2018. Negative Emissions Technologies and Reliable Sequestration: A Research Agenda. Washington, DC: The National Academies Press. doi: 10.17226/25259.
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Suggested Citation:"4 Bioenergy with Carbon Capture and Sequestration." National Academies of Sciences, Engineering, and Medicine. 2018. Negative Emissions Technologies and Reliable Sequestration: A Research Agenda. Washington, DC: The National Academies Press. doi: 10.17226/25259.
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Suggested Citation:"4 Bioenergy with Carbon Capture and Sequestration." National Academies of Sciences, Engineering, and Medicine. 2018. Negative Emissions Technologies and Reliable Sequestration: A Research Agenda. Washington, DC: The National Academies Press. doi: 10.17226/25259.
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Suggested Citation:"4 Bioenergy with Carbon Capture and Sequestration." National Academies of Sciences, Engineering, and Medicine. 2018. Negative Emissions Technologies and Reliable Sequestration: A Research Agenda. Washington, DC: The National Academies Press. doi: 10.17226/25259.
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Suggested Citation:"4 Bioenergy with Carbon Capture and Sequestration." National Academies of Sciences, Engineering, and Medicine. 2018. Negative Emissions Technologies and Reliable Sequestration: A Research Agenda. Washington, DC: The National Academies Press. doi: 10.17226/25259.
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Suggested Citation:"4 Bioenergy with Carbon Capture and Sequestration." National Academies of Sciences, Engineering, and Medicine. 2018. Negative Emissions Technologies and Reliable Sequestration: A Research Agenda. Washington, DC: The National Academies Press. doi: 10.17226/25259.
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Suggested Citation:"4 Bioenergy with Carbon Capture and Sequestration." National Academies of Sciences, Engineering, and Medicine. 2018. Negative Emissions Technologies and Reliable Sequestration: A Research Agenda. Washington, DC: The National Academies Press. doi: 10.17226/25259.
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Suggested Citation:"4 Bioenergy with Carbon Capture and Sequestration." National Academies of Sciences, Engineering, and Medicine. 2018. Negative Emissions Technologies and Reliable Sequestration: A Research Agenda. Washington, DC: The National Academies Press. doi: 10.17226/25259.
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Suggested Citation:"4 Bioenergy with Carbon Capture and Sequestration." National Academies of Sciences, Engineering, and Medicine. 2018. Negative Emissions Technologies and Reliable Sequestration: A Research Agenda. Washington, DC: The National Academies Press. doi: 10.17226/25259.
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Page 124
Suggested Citation:"4 Bioenergy with Carbon Capture and Sequestration." National Academies of Sciences, Engineering, and Medicine. 2018. Negative Emissions Technologies and Reliable Sequestration: A Research Agenda. Washington, DC: The National Academies Press. doi: 10.17226/25259.
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Page 125
Suggested Citation:"4 Bioenergy with Carbon Capture and Sequestration." National Academies of Sciences, Engineering, and Medicine. 2018. Negative Emissions Technologies and Reliable Sequestration: A Research Agenda. Washington, DC: The National Academies Press. doi: 10.17226/25259.
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Page 126
Suggested Citation:"4 Bioenergy with Carbon Capture and Sequestration." National Academies of Sciences, Engineering, and Medicine. 2018. Negative Emissions Technologies and Reliable Sequestration: A Research Agenda. Washington, DC: The National Academies Press. doi: 10.17226/25259.
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Page 127
Suggested Citation:"4 Bioenergy with Carbon Capture and Sequestration." National Academies of Sciences, Engineering, and Medicine. 2018. Negative Emissions Technologies and Reliable Sequestration: A Research Agenda. Washington, DC: The National Academies Press. doi: 10.17226/25259.
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Page 128
Suggested Citation:"4 Bioenergy with Carbon Capture and Sequestration." National Academies of Sciences, Engineering, and Medicine. 2018. Negative Emissions Technologies and Reliable Sequestration: A Research Agenda. Washington, DC: The National Academies Press. doi: 10.17226/25259.
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Suggested Citation:"4 Bioenergy with Carbon Capture and Sequestration." National Academies of Sciences, Engineering, and Medicine. 2018. Negative Emissions Technologies and Reliable Sequestration: A Research Agenda. Washington, DC: The National Academies Press. doi: 10.17226/25259.
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4 Bioenergy with Carbon Capture and Sequestration INTRODUCTION Combining the production of bioenergy with carbon capture and sequestration has the potential to lead to net negative emissions as carbon stored by photosynthesizing biomass growth is sequestered instead of being released to the atmosphere (IEA, 2011). The concept was first developed by Obersteiner et al. (2001) as a backstop climate risk measure, and by Keith (2001) as a potential mitigation tool. Since then, biomass energy with carbon capture and sequestration (BECCS) has come to be seen as one of the key carbon dioxide removal approaches needed to keep global atmospheric CO2 concentrations below 500 ppm and avoid catastrophic climate change. BECCS is largely used by integrated assessment models because the cost is low relative to the other low carbon technologies not included in the models and because the modules to represent other carbon dioxide removal technologies are undeveloped (e.g. direct air capture and soil carbon management are not included). In its Fifth Assessment Report, the IPCC concludes, from the literature review on mitigation scenarios developed with integrated assessment models, that many scenarios that met the Paris agreement’s objective to limit warming to 2°C select BECCS as the lowest cost option to reach temperature objectives in the second half of the century (high confidence), and that BECCS plays an important role in many low-stabilization scenarios (with limited evidence and medium agreement) (Fisher et al., 2007b). The International Energy Agency climate change models suggest that at least 2 Gt CO2 per year removal by BECCS should be implemented by 2050 to keep global temperature rise below 2°C (IEA, 2009). To put this in perspective, 1 Gt dry biomass is roughly equivalent to 1.4 Gt CO2 and 14 EJ primary energy and the U.S. annually emits about 6.5 Gt CO2 and consumes just over 100 EJ of primary energy. Still many policy-makers and academics are not aware of the pervasive and pivotal role that BECCS plays in climate change mitigation pathways despite still in its infancy (Anderson and Peters, 2016). BECCS typically refers to the integration of trees and crops that extract carbon dioxide from the atmosphere as they grow, the use of this biomass in power plants, and the application of carbon capture and sequestration via CO2 injection into geological formations. This chapter entails a much broader scope of biomass energy-based carbon removal pathways, including: 1) biomass combustion to thermal and electrical power with carbon capture and sequestration (traditional BECCS), 2) biomass thermochemical conversion to fuel with biochar soil amendment, and 3) biomass fermentation to fuel with carbon capture and sequestration (Figure 4.1). The scope of this chapter examines biomass energy in the forms of electricity, heat and fuels, and capture in the forms of CO2 and biochar. Compression, transportation and sequestration are covered in the geologic sequestration chapter.1 This chapter begins with a review of the various biomass energy-based carbon removal pathways and their commercial status. This is followed by an assessment of their removal and sequestration potential based primarily on biomass supply potential and process economics. Next is the Committee’s proposed research agenda for biomass energy-based carbon dioxide removal technology. 1 Given that costs for compression, transportation, injection and storage for CO2 captured both through BECCS and direct air capture are assumed to be approximately the same, the report discusses them once in Chapter 7 on Geologic Sequestration and Appendix F. PREPUBLICATION COPY 95

96 Negative Emissions Technologies and Reliable Sequestration: A Research Agenda a) b) c) FIGURE 4.1. Generic biomass energy-based carbon dioxide removal pathways: a) biomass-to-power with carbon capture and sequestration, b) biomass-to-fuel and biochar, and c) biomass-to-fuel with carbon capture and sequestration2. 2 Note that these closed carbon cycles are idealistic and that in reality carbon leakage could occur. For a more detailed discussion of leakage, see Chapter 7. PREPUBLICATION COPY

Bioenergy with Carbon Capture and Sequestration 97 FIGURE 4.2. Biomass energy carbon dioxide removal and sequestration steps covered in section. BACKGROUND Approach Description This section reviews the various technological pathways for biomass energy with carbon capture and sequestration by breaking up the pathways into four steps: 1) biomass production, 2) biomass transportation, 3) biomass conversion, and 4) carbon capture (Figure 4.2). Biomass Production Biomass feedstock may come from forest management (e.g. tree stems, branches, bark, logging residues, sawmill waste), agriculture (e.g. purposed-grown feedstock, crop residues), algae cultivation, or collection of municipal organic solid waste. Biomass sequesters atmospheric CO2 while growing, leading to an initial negative emission. The production and collection of biomass feedstock involve several activities such as seeding, fertilizer and pesticide production and spreading, tilling, logging roads, and tree harvesting, among others. Energy used in these activities is part of the life cycle assessment. The total managed land area in the U.S. potentially available for biomass production is nearly 900 Mha, though much of this land is already used for commodities such as food, forage, and fiber (Table 4.1). However, the biomass supply could be increased on most of this land without changing land use. An important caveat is that there is only one land base; therefore, in this study, the same land base described here for bioenergy is also considered as an option for forestry and agriculture carbon dioxide removal approaches. The discussion of how land use requirements for BECCS and other terrestrial approaches interact is found in the terrestrial chapter. On forest land, annual biomass production exceeds current harvest by about 70% (Smith et al., 2007) or 204 Mt/y dry biomass. Some of this could be harvested for bioenergy, although this would reduce the forest carbon stock and sink strength, and therefore the carbon removal benefit from forests would be correspondingly reduced. But, on forest land that is currently harvested, there is a significant amount of logging residues that is not currently utilized, and some of this is readily available for increasing bioenergy supply. Constraints on utilization of existing logging residue include economic feasibility of removing and transporting the biomass, and potential impacts on ecosystem productivity. Many U.S. States have regulations requiring that a certain amount (about 25%) of logging residue must be left on site to sustain productivity and wildlife habitat (Janowiak and Webster, 2010; Venier et al., 2014). How the residues would have been treated (e.g., left to decompose, burned, or used in a different wood product) and the rate of on-site decomposition also affect the carbon removal benefit. Croplands present opportunities to increase use of agricultural residues such as corn stover, much of which is currently not utilized. Settlements produce significant quantities of organic waste, much of which could be used to increase supply of biofuel. One of the more promising and potentially productive options would be to grow energy crops on land that is considered “marginally productive” for crops. There is a significant amount of marginal land in the U.S. and globally that could be converted to energy crops without affecting production of other commodities (more details in the terrestrial chapter). A good estimate of such land for the U.S. is the amount of farmland enrolled annually in the Conservation Reserve Program, which typically exceeded 8 Mha/ybefore area limits were established (Mercier, 2011). The productivity of biomass supply alternatives is highly variable both geographically and by source of biomass. Excluding wastes and residues, some categorical examples as well as a few specific PREPUBLICATION COPY

98 Negative Emissions Technologies and Reliable Sequestration: A Research Agenda bioenergy crop productivity estimates are shown in Table 4.2. These data highlight the variability in productivity within and between regions as a result of climate, site factors, and feedstock differences and provides a basis for the increase in biomass cost as the total biomass supply increases. Biomass Transportation Biomass must be transported from the source to the conversion facility or end user, where it will be converted to heat, electricity, or other fuels. This fuel must then be distributed to end users. A map of the distribution of biomass resources across the U.S., shown in Figure 4.3, shows that the east and west coasts and center of the U.S. have the most plentiful resources, while regions in between have far sparser supplies. Thus, these regions in particular would require biomass to be moved over substantial transportation distances for utilization. Even in the regions of more plentiful biomass supply, where shorter transportation distances can be expected, costs and emissions incurred by transportation can be substantial. TABLE 4.1. United States managed land area by land use category in 2015 in mega-hectares (Mha).2 Category 1 U.S. Forests 293 Croplands 163 Grasslands 325 Settlements 43 Wetlands 42 Other Land 23 Total 890 1 Defined by IPCC and the US EPA. 2 Data from EPA, 2017. TABLE 4.2. Productivity of selected bioenergy crops by region (tonnes per hectare).1 Crop Type/Species Northeast Southeast Delta Corn Belt Lake States Plains States Perennial grasses 9.0–16.8 7.8–21.3 6.7–15.7 9.0–15.7 1.8–11.2 4.5–14.6 Woody crops 11.4 11.2–12.3 — 7.8–13.4 7.8–13.4 7.8–13.4 Switchgrass 10.3–16.4 10.5–20.8 13.7–21.3 12.3–19.5 6.0–7.4 3.8–19.9 Poplar 9.9–13.2 9.0–14.8 10.5–14.6 10.3–15.0 8.3–13.0 5.8–12.5 Willow 8.5–16.4 8.5–16.8 10.8–12.5 8.7–18.4 8.3–15.9 3.1–13.9 Miscanthus 14.3–20.4 13.0–19.3 16.1–23.1 17.7–25.1 11.9–23.5 8.5–25.1 1From DOE, 2011, 2016. PREPUBLICATION COPY

Bioenergy with Carbon Capture and Sequestration 99 FIGURE 4.3. A map of solid biomass resources by county across the U.S. (NREL: https://www.nrel.gov/gis/images/biomass_2014/national_biomass_solid_total_2014-01.jpg) The results of an assessment of transportation costs for densified biomass, summarized in Figure 4.4, show that barge is by far the least expensive transportation mode for long distance domestic transportation where available (Gonzales et al., 2013). Barge access is quite limited, however, and the remaining options include truck and rail (results are specifically considering CSXT Corporation rail). Truck transportation is less expensive for relatively short distance transportation, and breakeven distances are presented in Figure 4.4. Furthermore, truck transportation can take advantage of the widespread road network in the U.S., as compared to the more limited rail network. At longer distances, rail is lower cost than truck transportation. In addition to cost, emissions associated with biomass transportation can be significant and should be accounted for in order to assess net carbon emissions from biomass utilization. Life-cycle assessments of greenhouse gas emissions in bioenergy production estimate emissions from biomass transportation based upon shipment method (road, rail, or sea) and transportation distance. Figure 4.5 shows an example of these estimates for dry biomass transport by truck, train or sea freight (Beagle and Belmont, 2016). Results show that truck transportation has significantly higher emissions per kilometer than train and sea freight. PREPUBLICATION COPY

100 Negative Emissions Technologies and Reliable Sequestration: A Research Agenda FIGURE 4.4. Transportation costs for a) grains and b) wood chips from Midwest to East and Southeast USA (Gonzales et al., 2013). FIGURE 4.5. Carbon dioxide and CO2 equivalent emissions per dry biomass produced as a function of transportation distance by road, rail, or sea. (Beagle and Belmont, 2016). Biomass Conversion In Figure 4.6, a detailed illustration of the many potential biomass-to-energy is provided. As indicated, these technologies are at a variety of technology readiness levels. This section describes two broad approaches to biomass conversion. Thermochemical. A number of thermochemical and biological routes for the conversion of biomass to energy have been demonstrated and implemented. Thermochemical routes broadly include pyrolysis, hydrothermal liquefaction, gasification, and combustion (Goyal et al., 2008). Pyrolysis approaches heat biomass in the absence of air (oxygen-deficient or anoxic) or in the presence of hydrogen (hydropyrolysis) to produce liquids and gases that can be upgraded to fuels or directly combusted and PREPUBLICATION COPY

Bioenergy with Carbon Capture and Sequestration 101 FIGURE 4.6. Biomass conversion pathways and technology readiness levels (TRL). (Adapted from Stafford et al., 2017). solid carbon-rich biochars that can be combusted, gasified, or sequestered as a soil amendment.3 Pyrolysis may proceed at high heating rates and short residence times to favor liquid yields (fast pyrolysis), or a slow heating rates and long residence times to favor solid carbon production (slow pyrolysis or carbonization). Hydrothermal liquefaction converts biomass at elevated temperatures and under high pressure steam to predominantly liquids products. Gasification, in contrast to pyrolysis and liquefaction, uses an oxidant (e.g.; steam, air, or carbon dioxide) to partially oxidize biomass to produce synthesis gas, composed of CO and H2 that can then be converted to liquid fuels via thermocatalytic processes, such as Fischer-Tropsch and methanol-to-gas (MTG); or directly combusted for heat and/or power generation. Finally, combustion uses air or pure oxygen gas to completely oxidize biomass to produce heat for direct use or for power generation. 3 The use of biochar as a soil amendment is discussed in the terrestrial chapter. PREPUBLICATION COPY

102 Negative Emissions Technologies and Reliable Sequestration: A Research Agenda Biological. In addition to thermochemical biomass-to-fuel conversion routes, there are a number of biological pathways to produce liquid and gaseous fuels (Antoni et al., 2007). Biological routes harness anaerobic digestion and fermentation to produce hydrogen, methane, and alcohol (e.g., ethanol) fuels. These biologically derived fuels can be burned directly for heat and power or upgraded to other fuels. An additional microbial route to biofuel production is the use of oil-producing microbes to directly generate biofuel precursors, such as the use of algae via photosynthesis. Carbon Capture and Sequestration The main carbon capture and sequestration pathways under consideration for biomass energy carbon removal are 1) biomass combustion or fermentation with CO2 capture, compression, and transportation to a geological site for long-term sequestration (transportation and sequestration are covered in the geologic sequestration chapter) and 2) biomass conversion to fuels with biochar (solid carbon) co-production that can be stored long-term as a soil amendment (see Chapter 7). Carbon Capture. Carbon dioxide capture technologies for biomass thermal and electrical power generation are generally the same as those currently under development for conventional fossil fuel power plant carbon capture and sequestration. Broadly, these technologies fall within four main categories: 1) post-combustion, 2) pre-combustion (or gasification), 3) oxy-combustion, and 4) chemical looping (Figure 4.7). While active research is ongoing in all of these categories for coal power plants, the different approaches vary significantly in technologic maturity. In Table 4.3, estimated technology readiness levels, carbon capture work, exergy efficiencies, levelized costs of electricity (LCOE), and carbon capture costs for the different coal power plant carbon capture approaches is presented. The fundamental challenge with carbon capture is achieving a pure stream of CO2 for sequestration that involves either separating oxygen from air before combustion or carbon dioxide from power plant exhaust after combustion. The exergy efficiency, calculated from ideal (minimum) work for separating gases over the estimated actual work to separate carbon dioxide, is used to provide a reference point for assessing both the overall energy requirement for carbon capture and benchmarking the state-of-the-art relative to what is theoretically possible. Note that these values are only for CO2 captured cost (energetic and financial), whereas CO2 avoided cost includes the compression, transport, and sequestration of the CO2 including the extra power and generated CO2 needed to carry out these operations. Carbon capture from fermentation processes, such as those used to produce ethanol, can utilize the same technology that is being developed for carbon capture in fossil fuel plants. Carbon dioxide is produced as a byproduct of the fermentation process itself, as well as from the power plant that supplies electricity and heat to the fermentation process. Therefore, both sources are candidates for CO2 capture. In the U.S. biorefineries currently emit about 45 Mt/y CO2 from fermentation, of which 60% could be captured and compressed at cost estimated to be under 25 $/t CO2 (Sanchez et al., 2018). Biochar Soil Amendment. The thermochemical conversion of biomass to fuels can produce 25-45% by mass biochar (solid carbon) as a byproduct, depending on the feedstock and process conditions (temperature, pressure, partial pressures, and residence times). The fraction of biochar production is important because it helps determine whether some biomass-to-fuels pathways are actually carbon negative (Del Paggio, 2017 webinar). Biochar soil amendment has been proposed as a promising path for long-term carbon removal strategy; however, questions remain about the long-term stability of biochar in soil environments. Proponents claim that biochar application reduces the burden on farmers in several ways: less fertilizer is needed because biochar absorbs, stores, and slowly releases nutrients such as phosphorus to plants and subsequently to the environment; biochar improves soil moisture retention, securing the crops against drought; farmers spend less on seeds as germination rates increase; biochar reduces the methane emissions from paddy fields and farmyard manures; it increases the soil microbes PREPUBLICATION COPY

Bioenergy with Carbon Capture and Sequestration 103 and other soil-life density; it lessens the hardening of soils; it supports better growth of roots and helps in reclaiming degraded soils (Jeffery et al., 2011). For additional details see Terrestrial Chapter. FIGURE 4.7. Simplified block diagrams of coal or biomass power with carbon capture approaches: 1) post- combustion, 2) pre-combustion, 3) oxy-combustion, and 4) chemical looping carbon capture. TABLE 4.3 Coal power plant carbon capture approach and estimated CO2 capture work, exergy efficiency, and cost for different carbon capture approaches, where exergy efficiency is the minimum work for carbon capture (0.2 GJ/tCO2 ) over the process exergy. (Bui et al., 2018). TRL CO2 Capture Exergy CO2Capture Carbon Capture Power LCOE Work Efficiency Cost References Approach Plant Type ($/MWhe) (GJ/t) (%) ($/t) 9 Rubin et Post-Combustion SCPC 1.0-2.6 8-21 94-130 36-53 al., 2015 7 Rubin et Pre-Combustion IGCC 1.1-1.6 12-18 100-141 42-87 al., 2015 SCPC/US 7 Rubin et Oxy-Combustion 1.3-1.7 12-15 91-121 36-67 C al., 2015 Chemical 6 CDCL ~ 2.1 ~9 ~ 101 ? Fan, 2012 Looping NOTE: SCPC (supercritical pulverized coal), IGCC (integrated gasification combined cycle), USC (ultra-supercritical), and CDCL (coal direct chemical looping). PREPUBLICATION COPY

104 Negative Emissions Technologies and Reliable Sequestration: A Research Agenda COMMERCIAL STATUS Biomass fueled power generation is commercially deployed across the US and world, although no biomass power plants are coupled with carbon capture and sequestration (CCS). Of the 4,000 TWh of electricity generated in the US in 2016, only 40 TWh was from wood-derived fuels and 22 TWh from other biomass sources, including municipal solid waste, agricultural byproducts and other biomass (EIA, 2017d). Large-scale biological biomass-to-fuel technology has been deployed commercially, mostly notably the production of approximately 370 million barrels of ethanol (EIA, 2017a). In Table 4.4 select biomass-to-fuel pathways, technology readiness levels, and developers is presented. Few of these projects have coupled the fuel production process with CCS. Among these, the largest is the Illinois Industrial Carbon Capture and Storage (IL-ICCS) project, where pure CO2 gas is formed as a byproduct of fermentation for ethanol production at an Archer Daniels Midland (ADM) plant near Decatur, Illinois is collected and injected into the nearby Mt. Simon Sandstone saline formation. This project plans to capture 0.9-1.0 Mt CO2 annually and began CO2 injection in 2017. This project follows on the completion of the Illinois Basin-Decatur Project, which captured and injected CO2 from the ADM plant to the Mt. Simon formation at a lower rate for three years. Notably, the ADM emits approximately 5 Mt/yr CO2, making the process net carbon positive due to CO2 emissions from the power plant. However, techno-economic studies have shown that such processes have the potential to be carbon negative if CCS is applied as across the entire chemical plant including the fermenter and power generation unit. Additionally, biocahr production is now a commercial activity with many producers located throughout North America. According to a recent survey commissioned by the US Forest Service (Draper et al., 2018) an estimated 39,000 - 77,000 t/y biochar are produced in the US and an additional 1,900 to 7,300 t/y are produced per year in Canada. Current biochar sales prices are around 1,800 $/t, with most consumers reportedly using it as a soil amendment to modify texture, increase porosity, improve water management and increase soil carbon. To increase market size, biochar producers are actively seeking biochar certification as an animal feed supplement, as is done in Europe. IMPACT POTENTIAL Availability of biomass feedstock is a critical issue when assessing the potential role of BECCS to mitigate climate change, and a wide range of values are available in the literature with order of magnitude uncertainties (Azar et al., 2010; Slade et al., 2014). For instance, Berndes et al., 2003 estimated the total annual contribution of biomass in the future global energy supply to be between 100 EJ and 400 EJ in 2050 based on a review of 17 published studies. High uncertainties associated with land availability, energy crop yields, and the future availability of waste, forest wood, and residues from forestry and agriculture are the main reasons for this wide range of values (Slade et al., 2014). In this section, the Committee presents an estimate of biomass potential for the United States and the world, associated negative CO2 flux, potential radiative impacts and costs for bioenergy with carbon capture. Carbon Flux Based upon estimated US biomass availability data, summarized in Table 4.5 and assumptions discussed in detail below, the economically feasible--without significant impacts on current land and biomass use— BECCS CO2 flux potential is estimated. The U.S. economically feasible lower-bound BECCS CO2 flux potential is estimated to be 522 Mt/y CO2 . This estimate is based on the following assumptions: ● No energy crops are utilized for BECCS. Although high levels of BECCS deployment depend on productivity increases on the order of 1% annually, energy crops are eliminated from the lower- bound estimate because there is currently no widespread energy crop production and utilization, PREPUBLICATION COPY

Bioenergy with Carbon Capture and Sequestration 105 and there are significant concerns regarding impacts on climate and food security from increasing energy crop production as explained in section 4. Indeed, as shown by Heck et al., 2018, the potential for BECCS from dedicated bioenergy plantation is marginal if we use precautionary guardrails in order to stay within planetary boundaries for non-climate impacts such as biodiversity or freshwater use. ● Agricultural byproducts are included in an amount equal to the difference between economically feasible production in 2040 and the current utilization level in order to avoid displacing demand and creating new needs that might lead to land burden (annual flux = 113 MtCO2/yr). ● Economically recoverable and currently unused forestry logging residues and other wood wastes are included based upon 2040 availability. Whole-tree biomass from thinnings and fuel treatments, and wood currently used for home and industry heating, is not included because there are expected to be barriers to these sources such as concerns about impacts on intact forests (annual flux = 123 Mt/y CO2). TABLE 4.4. Select biofuel processes, developers, and technology readiness levels (TRL). (Sources: Stafford et al., 2017 and IRENA, 2016). Feedstock Process Product Developer TRL Algae Hydrothermal Liquefaction Liquid Hydrocarbons PNNL/Genifuels 6 Fermentation Ethanol KIIT 6 Extraction Biodiesel RIIHL 7 Sugar/Starch Anaerobic Digestion Methane (many) 10 Fermentation Butanol Green Biologics 8 Fermentation Ethanol (many) 10 Aqueous Phase Reforming Liquid Hydrocarbons Virent/Shell 3 Organic Waste Aqueous Phase Reforming Liquid Hydrocarbons Virent 3 Hydrothermal Liquefaction Liquid Hydrocarbons PNNL/Genifuels 4 Anaerobic Digestion Methane (many) 10 Gasification Ethanol Enerkem 8 Gasification Ethanol LanzaTech 8 Hydropyrolysis Liquid Hydrocarbons CRI/GTI 6 Oil Crops/Waste Anaerobic Digestion Methane (many) 10 Extraction Vegetable Oil (many) 10 Extraction Biodiesel (many) 10 Lignocellulose Hydrothermal Liquefaction Biocrude Licella 5 Densification Pellets many 10 Torrefaction Torrefied Biomass Arbaflame, SINTEF 8 Anaerobic Digestion Methane (many) 9 Fermentation Butanol Green Biologics 9 Fermentation Ethanol (many) 10 Pyrolysis Charcoal/Biochar (many) 10 Pyrolysis Liquid Hydrocarbons (many) 5 Hydropyrolysis Liquid Hydrocarbons CRI/GTI 8 Gasification Liquid Hydrocarbons (many) 7 NOTE: CRI (CRI Catalyst Company, Shell Group), GTI (Gas Technology Institute), KIIT (Korea Institute of Industrial Technology), PNNL (Pacific Northwest National Laboratory), RIIHL (Reliance Industrial Investments and Holdings), Adapted from: Stafford et al., 2017. PREPUBLICATION COPY

106 Negative Emissions Technologies and Reliable Sequestration: A Research Agenda ● Organic wastes, the majority of which is comprised of municipal solid waste, are included based upon 2040 availability (annual flux = 286 MtCO2/yr). The US economically feasible upper-bound BECCS CO2 flux potential is estimated to be 1,500 Mty CO2/based upon all available agricultural byproducts, energy crops, forestry waste and byproducts, and organic waste. This flux corresponds to the total carbon content of available biomass and does not account for losses and other GHG emissions throughout the supply chain. It also does not take into account the land demands or conflicts that might arise at maximum flux values. Therefore, it is not considered as safely achievable. TABLE 4.5. Estimated United States dry biomass potential and equivalent CO2 fluxes in megatonnes per year (Mt/y), including current levels of biomass utilization, lower and upper-bound dry biomass potentials for different feedstock types, and associated CO2 flux potentials, assuming all biomass carbon content is captured and sequestered regardless of biomass conversion path. Current 2017 2040 Use Technical Economically Technical Economically Source Potential Feasible Potential Feasible CO2 CO2 CO2 CO2 Biomass Biomass Biomass Biomass Biomass Flux Flux Flux Flux Agricultural 130 154 269 125 218 219 382 195 339 Byproducts Agricultural residues ― 106 185 94 164 171 298 161 280 Agricultural wastes ― 48 84 31 54 48 84 34 59 Energy Crops 0.087 503 875 ― ― 503 875 373 649 Switchgrass ― ― ― ― ― ― ― 146 254 Miscanthus ― ― ― ― ― ― ― 145 253 Biomass sorghum ― ― ― ― ― ― ― 17 30 Energy cane ― ― ― ― ― ― ― 0 0 Non-coppice ― ― ― ― ― ― ― 41 71 Coppice ― ― ― ― ― ― ― 24 41 Forestry 132 332 609 124 228 332 609 122 225 Logging residues ― 43 78 16 30 43 78 19 35 Whole-tree ― 143 263 64 117 143 263 55 102 Other wood wastes ― 146 268 44 82 146 268 48 88 Organic Waste 36 259 240 259 240 309 286 309 286 Municipal solid waste 30 203 166 203 166 242 198 242 198 Construction & ― 46 68 46 68 54 81 54 81 demolition Sewage & 6 10 6 10 6 12 7 12 7 wastewater Total 298 1248 1993 508 686 1363 2152 999 1499 SOURCES: DOE, 2016; EPA, 2016a; Rose et al., 2015; Seiple et al., 2017; USDA, 2014. PREPUBLICATION COPY

Bioenergy with Carbon Capture and Sequestration 107 The global upper-bound BECCS CO2 flux potential is estimated to be 10-15 Gt/y CO2by 2050 according to the IPCC (IPCC, 2014). The lower bound flux is assessed using a reduction factor based upon the maximum versus lower bound US fluxes. This approach assumes that globally available biomass has a similar composition and source distribution as US biomass supply and is subject to similar restrictions. While this assumption is likely flawed, it provides a coarse assessment of global flux potential. The US lower bound range is approximately 35% of the maximum potential flux; thus, the global lower bound BECCS CO2 flux potential is estimated to be 3.5-5.2 Gt/y CO2 by 2050. Agricultural Byproducts Agricultural byproducts include residues and waste streams, as defined and summarized in the Department of Energy’s 2016 Billion-Ton Report (DOE, 2016). The current consumption of all agricultural byproducts for energy production was also given by DOE, 2016 based on 2014 EIA data, including the byproducts used (9.5 Mt) for annual heat and power production, as well as the substantially larger amounts of agricultural biomass that is currently used each year for fuel and bio-based chemical production (approximately 115 Mt and 5.3 Mt, respectively). While carbon composition of agricultural residues can vary, an average carbon content of 47.5% by mass was used to evaluate CO2 production. Agricultural Residues. Agricultural residues include corn stover, wheat straw and sorghum, oat and barley residues. Technical potential is defined in this report as the total resource available, and availability in the years 2017 and 2040 were estimated from the agricultural residues available at 88 $/t dry biomass ($80 per short ton), based on DOE, 2016 under a base case scenario of 1% annual growth in yield. These quantities were used as reasonable estimates of total availability because the production curves presented in the report show minimal increase in potential production with increase in farmgate price above 88 $/t and up to 110 $/t. The economically feasible quantities of agricultural residues presented in Table 4.5 were gathered from DOE, 2016 for years 2017 and 2040 under the scenario of 66 $/t farmgate price and 1% annual growth. Agricultural Waste Streams. Agricultural waste streams include sugarcane bagasse and trash, soybean hulls, rice hulls and straw, grain dust and chaff, orchard and vineyard prunings, cotton gin trash and field residue, and animal manure. While animal fats and yellow grease were also included in the agricultural waste resources identified in DOE, 2016, these were not included in total agricultural waste stream assessment in this report because their likely utilization pathway is the production of biodiesel. While biodiesel displaces fossil-derived fuels, neither of the carbon negative pathways identified in this report (combustion with CO2 capture or pyrolysis with biochar sequestration) are achieved via biodiesel. Technical potential and economic feasibility were estimated for years 2017 and 2040 from data provided by the BT16 report, where economic feasibility under the scenario of 66 $/t farmgate price and 1% annual growth was used in this report. Energy Crops Current production for herbaceous energy crops comes from the most recent 2012 USDA census (USDA, 2014) as presented in DOE, 2016. On the one hand, this value may be overestimated because it includes non-energy uses such as animal bedding. On the other hand, it might also be underestimated because producers often do not report planting of unique crops because they are not enrolled in federally subsidized programs or the crops are grown on non-private agricultural lands such as public universities. However, this value is so low that a potential under- or overestimation is probably negligible. PREPUBLICATION COPY

108 Negative Emissions Technologies and Reliable Sequestration: A Research Agenda Current production for woody energy crops comes from the most recent 2012 USDA census (USDA, 2014). The value available on the USDA website is in acres of crops for short-rotation woody crops. This value has been converted into annual production (Mt/y) by multiplying the acres of crops by the average dry biomass yield per acre (t/acre). The average yields used are the mean region-specific yields for poplar and willow crops from DOE, 2016. Theoretically, the technical potential for biomass production from energy crops is very high as all crops in the US could be converted to energy crops. However, this would be a very unrealistic scenario. Therefore, a very rough estimate of the current technical potential has been calculated, considering that the difference between current total croplands and harvested croplands according to the USDA, 2014) could be cultivated as energy crops. In the USDA census, total croplands include “cropland harvested, other pasture and grazing land that could have been used for crops without additional improvements, cropland on which all crops failed or were abandoned, cropland in cultivated summer fallow, and cropland idle or used for cover crops or soil improvement but not harvested and not pastured or grazed”. This area was then converted into dry production per year (Mt/y) by multiplying it by the average yield (t/acre) for all six energy crop types presented by DOE, 2016. Economically feasible biomass productions are detailed for each type of biomass assessed in DOE, 2016, i.e. switchgrass, miscanthus, biomass sorghum and energy cane for herbaceous crops and non-coppice (poplar, pine) and coppice (willow, eucalyptus) for woody crops. They are taken from the 2016 Billion-Ton Report for a 1% annual yield increase and a biomass price at farm gate of less than 66 $/dry biomass. Achieving this 1% annual yield increase would require research to genetically modify herbaceous crops and develop silvicultural systems that target biomass production rather than wood volume or quality (Dietrich et al., 2014; Lotze-Campen et al., 2010; Robison et al., 2006). The DOE (2016) assumes agricultural lands to stay constant over the years. Therefore, additional energy crops replace other types of current crops such as food crops. In 2040, 8.3% of agricultural lands are devoted to energy crops under the 1% annual yield increase and 66 $/dry biomass scenario. There are no economically feasible production values for 2017 in DOE (2016) because of the constraints included in the model, such as. agricultural biomass feedstock all comes from residues. The annual CO2 flux potential was calculated based on a 47.5% carbon mass content in dry biomass. Indeed, Schlesinger and Bernhardt, 1991 have found that dry biomass carbon content is almost always between 45% and 50% by weight. Therefore, the mean value has been used. This is an estimation of the amount of CO2 sequestered from the atmosphere during biomass growth that could then be stored using BECCS technologies. However, this is not an estimation of the net potential for CO2 sequestration from BECCS. Indeed, the specific carbon capture and sequestration process efficiency, as well as other life cycle emissions, including reduction of land carbon stock, significantly affect the CO2 flux potential. Forestry The U.S. is the largest producer of industrial roundwood products in the world, accounting for 19% of the global total. Other countries, particularly in the tropics, use most of harvested roundwood for heating and fuel consumed by households (FAO, 2015b). The large base of industrial timber production in the U.S. drives fuelwood use, which is mostly associated with timber harvesting for other products such as paper and lumber. The main resource categories are logging residues, increased whole-tree harvest of green or damaged timber, and other wood wastes, which includes unused mill and urban wood residues (Perlack et al., 2005). Currently, the U.S. uses about 132 Mt annually of wood and wood waste for thermal and electric power and has the potential to nearly double this amount at a dry biomass price of 66 $/t based on economic modeling that excludes potential additional supplies from lands more than a 0.8 km (0.5 mi) from a road, protected areas, and steep slopes (DOE, 2016). With the exception of whole-tree harvest, potential additional wood for bioenergy is associated with improving utilization of timber and residues associated with current levels of timber harvest for other products; therefore, coupled with supply-area PREPUBLICATION COPY

Bioenergy with Carbon Capture and Sequestration 109 restrictions, there would be limited consequences for other forest values. Increasing whole-tree harvest is restricted by the amount of wood growth that exceeds current harvest, so that the potential increase is sustainable as long as growth is not impacted by factors such as increasing natural disturbances and climate change. However, the area that is harvested is highly variable among the scenarios modeled, indicating that there are potential impacts on net greenhouse gas emissions and other values of impacted forests over time. Globally, 1,194 Mt/y wood biomass are used for fuel, mostly for household fuel and charcoal, approximately equal to the amount of industrial wood produced annually (FAO, 2016). The potential additional supply of wood for industrial biofuel at the global scale is not well known but could range from 1,316 - 10,532 Mt/y dry biomass (FAO, 2016). Because of significant differences between current U.S. and global fuelwood use infrastructure, the pathways to large-scale deployment of BECCS may require different strategies. Much of the fuelwood in the U.S. is used in association with production of paper and other wood products at existing manufacturing facilities that are widely spread around the southern U.S. and to a lesser extent elsewhere (DOE, 2016). In contrast, global fuelwood use is even more dispersed particularly in tropical areas where large wood processing facilities are mostly absent. Organic Waste Biogenically derived organic wastes and CO2 fluxes potentials were estimated from three waste streams: (1) municipal solid waste, (2) construction and demolition, and (3) sewage and wastewater. Municipal Solid Waste. The U.S. EPA estimated the U.S. generated 230.5 Mt dry municipal solid waste in 2013 (4.4 lb/d per person); of which 70.3% was biogenic (paper 27.0%, food 14.6%, yard waste 13.5%, wood 6.2%, and leather, textiles, and rubber 9.0%) (EPA, 2016a). Using these data and U.S. Census Bureau population estimates (Colby and Ortman, 2015), the dry biomass from municipal solid waste is estimated to be 167 Mt in 2017 and 199 Mt in 2040 (Table 4.5). Annual carbon dioxide equivalent flux potential of 166 Mt in 2017 and 198 Mt in 2040 is estimated using the municipal solid waste CO2 emissions per dry biomass factor of 0.82 t/t (EPA, 2014) (Table 4.5). Construction and Demolition. The U.S. EPA estimated the U.S. generated 481 Mt construction and demolition waste in 2013 (9.2 lb/d per person); of which 7.6% was biogenic (wood). Using these data and U.S. Census Bureau population estimates (Colby and Ortman, 2015), the annual dry biomass from construction and demolition waste is estimated to be 37 Mt in 2017 and 44 Mt in 2040 (Table 4.5). From this, annual CO2 equivalent flux potentials of 68 Mt in 2017 and 81 Mt in 2040 were estimated using a wood waste CO2 emissions per dry biomass factor of 1.5 t/t (EPA, 2014). Sewage and Wastewater. Seiple et al., 2017 estimated that the U.S. produces 12.56 Mt/y dry biomass of wastewater sludge, of which about 50% in beneficially used (6.23 Mt/y). Rose et al., 2015 reported a median human stool and urine dry solids generation rates of 29 g/d and 59 g/d, respectively for a combine median dry biomass generation rate of 88 g/d per person. Using this median generation grate and U.S. Census Bureau population estimates (Colby and Ortman, 2015) , the annual dry biomass from human sewage is estimated to be 10 Mt in 2017 and 12 Mt in 2040 (Table 4.5). Assuming dry human stool and urine have a carbon content of 20% and 13% by mass (Rose et al., 2015), then the annual CO2equivalent flux potentials from human sewage are estimated to be 6 Mt in 2017 and 7 Mt in 2040. PREPUBLICATION COPY

110 Negative Emissions Technologies and Reliable Sequestration: A Research Agenda Carbon Capacity According to the IEA, 2016, most climate scenarios that keep average global temperature rise below 2°C include at least 14 Gt CO2 cumulative removal from BECCS globally by 2050, or about 2% cumulative global emissions reduction. If the U.S. were to commit to removing a proportional share of CO2 emissions (15% of global emissions in 2015), then the U.S. will need to remove 2.1 Gt CO2 by 2050. Supply Capacity Basis The United States lower-bound cumulative CO2 storage capacity based on biomass supply achievable with minimal impacts on current land and biomass use is 6.0 Gt CO2 by 2040, if annual CO2 sequestration is ramped linearly from 0% to 100% of the lower-bound CO2 flux potential (522 Mt/y CO2) from 2018 to 2040. If continued at the same rate, the lower-bound cumulative CO2 storage capacity is 11 Gt CO2 by 2050. The U.S. upper-bound CO2 storage capacity based on biomass supply achievable with minimal impacts on current land and biomass use is 17 Gt CO2 by 2040, if annual CO2 sequestration is ramped linearly from 0% to 100% of the upper-bound CO2 flux potential (1,500 Mt/y CO2) from 2018 to 2040. If continued at the same rate, the upper-bound cumulative CO2 storage capacity is 32 Gt CO2 by 2050. The worldwide lower-bound CO2 capacity is assessed by scaling the total global capacity by the same reduction factor utilized in the U.S. A comparison of upper and lower bounds for total U.S. CO2 capacity shows that lower bound capacity is 35% of upper bound capacity; thus, the global lower-bound CO2 storage capacity is estimated to be 57-86 Gt CO2 by 2050 if the annual CO2 sequestration rate is increased linearly from 0% to 100% from 2018 to 2050. Based upon the range of upper-bound global CO2 flux potentials (10-15 Gt/y CO2), the Total global upper-bound cumulative CO2 capacity is estimated to be 165-248 Gt CO2 by 2050. Sequestration Capacity Basis One constraint on the carbon sequestration potential for biomass energy removal pathways is the availability and economic viability of carbon storage resources. For biomass combustion and fermentation pathways, the limitation is the availability and capacity of geological sequestration (see Chapter 7). For biomass thermochemical conversion to fuels with co-production of biochar, there is no apparent technical or economic limits to the amount of carbon that can be stored, whether it be stored as a soil amendment or in landfills. Radiative Impacts In the review by Creutzig et al., 2015 , five main sources of radiative (life cycle) impacts for bioenergy systems were identified: (1) greenhouse gas emissions from fossil fuels used along the value chain, (2) greenhouse gas emissions associated with biomass or biofuel combustion, (3) greenhouse gas emissions and uptakes from land disturbances, (4) emissions of short-lived climate forcers (e.g. black carbon) from biomass or biofuel combustion and of non-CO2 GHGs (e.g. CH4, N2O) from land management, and (5) climate forcing resulting from alteration of the land surface (e.g. albedo changes). A life-cycle approach is essential to account for all greenhouse gas emissions and uptakes associated with BECCS technologies in order to determine their net contribution to climate change mitigation. Bioenergy with carbon capture and sequestration involves both fossil and biogenic carbon flows. Biogenic carbon flows consist in the uptake of CO2 from the atmosphere by growing biomass during photosynthesis, and by CO2 emissions from biological respiration, degradation, and combustion. PREPUBLICATION COPY

Bioenergy with Carbon Capture and Sequestration 111 FIGURE 4.8. Carbon flows for switchgrass burned in an integrated gasification combined cycle facility retrofitted to burn biomass with carbon capture and sequestration (from Smith and Torn, 2013). Fossil carbon flows consist of the CO2 and CH4 emissions from the combustion of the fossil fuels or materials needed by BECCS technologies. For example, transport of biomass by fossil-fuel powered vehicles or locomotives must be accounted for in estimating net carbon removal. Further, CO2 is not the only greenhouse gas contributing to climate change, and methane (CH4) and nitrous oxide (N2O) are especially relevant for biomass systems. For instance, 75.1% of U.S. N2O emissions in 2015 were attributed to agricultural soil management through activities such as fertilizer application and other practices that increase nitrogen availability in the soil (US EPA, 2017). Methane is also emitted by biological respiration, degradation and combustion, and biomass decomposition in anaerobic conditions could lead to high CH4 emissions. Other greenhouse gas emissions can also occur at different stages of BECCS process life cycle. For instance, natural gas can be used in biomass conversion processes, leading to CH4 emissions. In Figure 4.8, an example of “carbon losses” associated with BECCS for switchgrass burned in an integrated gasification combined cycle power plant with carbon capture and sequestration is presented (data taken from the literature). Fully accounting for net changes in carbon stocks and fluxes on land associated with bioenergy is an important element contributing to the net effect of BECCS on the atmosphere. The source of biomass, whether live vegetation or waste, determines the essential accounting elements. In calculating effects on net CO2 balance, it is necessary to compare temporal bioenergy production scenarios with a projected business as usual baseline or reference scenario to accurately reflect the incremental net change in emissions. The time horizon is important in several ways. Depending on the bioenergy source, it will take different times to recover the utilized biomass (sometimes called “re-paying carbon debt”), and additional “time to carbon sequestration parity” which refers to the point at which the accumulated net (or “additional”) greenhouse gas effect from using the bioenergy equals the net greenhouse gas effect of the baseline (often a “no-harvest” scenario) (Ter-Mikaelian et al., 2015). In sharp contrast to harvesting live trees, which may take decades or centuries to recover their original biomass and reach carbon sequestration parity, using wood residues for bioenergy that would otherwise have been left to decompose or slash-burned results in emissions reductions over a shorter term. On the other hand, if the wood residues would otherwise have been used in a long-lived product such as particle board, it could take decades for the use of this material for bioenergy to have a positive effect of reducing atmospheric CO2. Indirect effects, such as broader impacts on land use and supply of other wood products, and consequent impacts on greenhouse gas emissions are important to consider in calculating the overall net CO2 balance. PREPUBLICATION COPY

112 Negative Emissions Technologies and Reliable Sequestration: A Research Agenda Land-cover changes or land use disturbances (e.g. forest harvesting or conversion of natural lands to crops) can also lead to changes in albedo (Betts and Ball, 1997; Zhao and Jackson, 2014), surface roughness and evapotranspiration (Swann et al. 2010), influencing the climate system. Albedo changes are found to be the dominant effect, especially in areas with seasonal snow cover (Bathiany et al., 2010), and can possibly be stronger than those of associated biomass carbon sequestration (Bernier et al., 2011; Betts, 2000; Jones et al., 2013b; O'Halloran et al., 2012). Although these biogeophysical climate impacts can be very important, it is still difficult to quantify them at large-scale because they are site specific and show important variations in magnitude across different geographic regions (Anderson-Teixeira et al., 2012). ESTIMATED COSTS OF IMPLEMENTING BECCS The extent to which BECCS is implemented is expected to be highly dependent on factors such as biomass supply costs and the costs of competing electricity generation approaches, such as natural gas. These costs are summarized below, followed by specific estimates of carbon costs for CO2 generated and captured in a power plant and biochar produced by pyrolysis. Biomass Supply Costs Cost per ton of biomass supply is affected by many factors: productivity or yields per hectare, transportation (distance from roadside), fertilizer additions, processing, stumpage price or payment to grower, harvest cost, and other feedstock specific factors (DOE, 2011). In Figure 4.9, the rise in prices for each category of feedstock as the total supply increases is highlighted, and it shows the relative availability of different feedstocks at different levels of supply. FIGURE 4.9. Potential forestry, agricultural, and waste biomass resources shown as a function of marginal and average roadside dry biomass prices in 2040 (DOE, 2016). PREPUBLICATION COPY

Bioenergy with Carbon Capture and Sequestration 113 TABLE 4.6. Estimated levelized cost of electricity (LCOE) based on weighted average of regional values based on projected capacity additions for new U.S. power plants entering service in 2022. (Source: EIA, 2017c) Capacity Levelized Cost of Electricity ($2016/MWhe) Factor Power Plant Type Transmissio Capital Fixed Variable n Total Cost O&M O&M Investment Natural Gas 87% 14.0 1.4 42.0 1.1 58.6 Biomass 83% 47.2 15.2 34.2 1.2 97.7 Electricity Costs Carbon dioxide capture, compression, and transportation to a site for geological sequestration is considered primarily for use with biomass-fueled combustion for thermal and electrical power generation, as opposed to producing fuels. The primary challenge for biomass electrical power with carbon capture and sequestration is the comparatively low power plant efficiency (typically under 25%) of biomass power plants. Low biomass power plant efficiency effectively increases the already high cost of feedstocks (50-80 $/t or 3-4 $/GJ dry biomass) and capital costs of biomass power plants (over 4,100 $/kW electricity) that ultimately results in an uncompetitive levelized cost of electricity of about 100 $/MWh ($28/GJ), Table 4.6 (EIA, 2017c). By contrast, conventional natural gas combined cycle power plants have higher efficiency (typically over 45%) and low fuel costs (2-3 $/GJ or $2-3/Mcf natural gas) and low capital costs (under $920/kW electricity) that yields levelized costs of electricity of about 60 $/MWh (17 $/GJ)—nearly half the cost of biomass electrical power. Given this fact, biomass energy with carbon capture for electrical power research and development should prioritize increasing biomass power plant efficiency over carbon capture, compression, and transportation research and development. Biomass-to-Power with Carbon Capture Two factors are considered for the economics of biomass-power generation with carbon capture: the levelized cost of electricity (LCOE) and the cost of carbon capture. Based on data provided to the Federal Energy Regulatory Commission (FERC, 2016), the EIA estimated that in 2016 the levelized cost of electricity for an average coal power plant was 36.1 $/MWh—comprising 5.1 $/MWh operations, 5.5 $/MWh maintenance, and 25.5 $/MWh fuel costs. Assuming operations and maintenance costs are not substantially different between a coal to biomass power plant, an estimate of biomass-derived electricity cost can be made by considering the current costs of electricity production in fossil-fueled power plants and modifying those costs to consider biomass feedstock costs and carbon capture costs. For a simple and direct comparison of fuels, biomass power plant efficiency is assumed to be the same as coal, even though efficiencies are highly dependent upon firing percentage and biomass pretreatment, such as torrefaction or densification. According to the U.S. EIA, 2017b, the average coal power plant efficiency was 32.5% in 2016. Assuming a biomass higher heating value of 17 GJ/t (about half that of coal) and farmgate cost of 66 $/t, the farmgate biomass cost contribution to biomass levelized cost of electricity cost is 43 $/MWh— nearly 70% higher than coal. Biomass transportation contributes another 14 $/MWh to biomass electricity costs, assuming transportation costs equivalent to coal at 22 $/t (EIA, 2017b). Combining biomass farmgate and transportation costs, the total fuel contribution power plant electricity costs is 57 $/MWh— more than twice that of coal at 26 $/MWh. Since fuel costs dominate the levelized cost of electricity, substituting biomass for coal has a significant impact on electricity costs, levelized cost of electricity increasing from 36 $/MWh for coal to 67 $/MWh for biomass. PREPUBLICATION COPY

114 Negative Emissions Technologies and Reliable Sequestration: A Research Agenda Inclusion of CO2 capture adds additional cost to the plant. Using an estimated post-combustion carbon capture cost of 46 $/t CO2 (Rubin et al., 2015), carbon capture adds 52 $/MWh to electricity generation costs. Thus, the total estimated biomass power with carbon capture levelized cost of electricity is about 119 $/MWh. Assuming a carbon content of 47.5% by mass across all biomass types, the total cost to generate and capture CO2 from a biomass power plant is 105 $/t CO2 and the differential cost from a baseline coal-fired power plant without carbon capture is about 70 $/t CO2. Biomass-to-Fuel with Biochar Carbon Sequestration Currently, most thermochemical approaches to convert biomass to fuel are optimized for maximum fuel production, where the co-produced biochar is burned to provide process heat. If we assume that the biochar is instead used as a soil amendment to sequester carbon in the soil (or simply buried) and this process heat was instead provided by natural gas at a price of 2-7 $/GJ (2-7 $/Mcf), by proxy the effective biochar carbon capture cost would be about 37-132 $/t CO2. Given the ease of separating biochar and assuming biochar is stored locally and suffers little oxidation to CO2 in storage, the cost of CO2 “avoided” will be nearly the same as “captured”. Note that this estimate of carbon capture cost does not assume any cost offset from the sale of biochar to agriculture users as the biochar market size is currently small relative to the scale necessary to provide climate benefits. Recently, the USDA commissioned a survey of US biochar industry and estimated the current biochar market to be in the range of 35,000 to 70,000 t/y—roughly equivalent to sequestering 75,000 to 150,000 t/y CO2,eq (USDA, 2018). Reported biochar sales prices ranged widely from a low of 600 $/t and an average price of 1030 $/t, assuming a carbon content of 60% by weight, these prices correspond a carbon price of 1320-2270 $/t CO2,eq.. SECONDARY IMPACTS The IPCC has paid little attention to non-climate impacts on ecosystems and biodiversity from large-scale CO2 removal technologies such as BECCS (Williamson, 2016). However, several publications in the past years have addressed a set of different types of environmental and societal impacts associated with bioenergy and BECCS. Aside from physical constraints on biomass production, life cycle GHG emissions and other potential radiative impacts addressed in section 3, there are key uncertainties regarding indirect emissions, adverse effects on food security, impacts on biodiversity and land conservation, competition for water resources, social equity and social acceptance issues (Sanchez and Kammen, 2016). Environmental Impacts The area of land required per unit mass of carbon removed from the atmosphere is particularly important for BECCS, leading to different potential impacts regarding land use change, land conservation (e.g. nutrient availability), and biodiversity. Some researchers have provided evidence that suggest some types of BECCS are incompatible with human development within safe operating margins, as they begin to threaten planetary boundaries, such as biosphere integrity and nitrogen flows (Heck et al., 2018). As described above, both U.S. and global lower-bound estimates for BECCS would not require any land use changes, since biomass would be sourced from waste and residues from existing land uses. The U.S. upper-bound estimate of 1.5 Gt/y CO2, based on an average productivity of 18 t/ha CO2,eq (Table 4.2) indicates a land area requirement of about 78 Mha. For the global upper-bound estimate of 10-15 Gt/y CO2, Smith et al., 2016 estimated a global land area required to deliver just 12 Gt/y CO2,eq is about 380- PREPUBLICATION COPY

Bioenergy with Carbon Capture and Sequestration 115 700 Mha for all sources including wastes and residues from existing land uses, and dedicated energy crops such as willow and poplar or miscanthus on a range of productivity classes. This land area represents 36% to 163% of land identified as abandoned or marginal4 (Canadell and Schulze, 2014). Similarly, Humpenöder et al., 2014 found the land requirements to range from 300-500 Mha, depending on whether afforestation was also a major part of a carbon dioxide removal program. Carbon removal through afforestation and reforestation also requires large areas of land (~2,800 Mha), potentially an order of magnitude greater than that required for BECCS, (see Chapter 3, Figure 3.3) (Humpenöder et al., 2014). This figure shows the simulated time series of global land use for BECCS and forestry NETs. Therefore, large-scale implementation of BECCS is expected to compete with afforestation/reforestation, as well as with food production and delivery of other ecosystem services (e.g. Bustamante et al., 2014). Nutrient removal associated with biomass harvesting (for energy crops as well as collecting agricultural and forest residues instead of letting them on the ground as nutrients) differs several-fold among biomass sources. Such nutrient removal prevents further emissions from decomposition of the biomass, but it could lead to nutrient depletion depending on the vegetation or other land use replaced (Smith et al., 2016). Moreover, enhanced cropping will increase nutrient runoff to the sea and resultant eutrophication, which could lead to reduced coastal fisheries yields and potential negative impacts on coastal blue carbon. The use of bioenergy feedstock with low nutrient concentrations such as residues, forest and lignocellulosic biomass could help mitigating nutrient depletion and runoff. Bioenergy feedstock from food and fiber production waste does not have a direct effect on existing land use. However, establishing new dedicated bioenergy feedstock production capacity will initiate direct competition with other land uses, unless the land is marginally productive and not actively managed at present. These direct and indirect effects should be considered in the overall accounting for net effects on CO2, and if significant, can be quantified using an integrated economic-land use modeling approach (Plevin et al., 2010; Searchinger et al., 2008). In addition to effects on land use, there may be effects on commodity supplies and prices for goods that may use the same material, for example, wood products (Ahlgren et al., 2013). Changes in production of other goods may in turn affect CO2 balance because of differences in production systems and use and disposal patterns of biomass products, and potentially other materials that can be substituted for biomass products. Moreover, the modeling approach selected to predict these indirect effects should consider the entire world because of globalized food and material markets. Unirrigated bioenergy crops cause evaporative losses that are higher than that of average short vegetation (Smith et al., 2016). Irrigated bioenergy crops can reduce the pressure on land due to higher yields, while increasing the pressure on freshwater ecosystems and competition with other users, leading to a trade-off between land and water requirements (Bonsch et al., 2016). Important water withdrawal for energy crops irrigation could lead to freshwater ecosystem degradation and aquatic biodiversity loss. Moreover, the CCS process also requires the use of water. Smith et al., 2016 estimate the amount of water required to deliver 12 Gt/y CO2,eq sequestration through BECCS to approximately 3% of the total amount of water currently used by human activities. However, water can also be extracted from CO2 storage operations so that water use associated with the carbon capture and storage process is case- specific. Integrated assessment models are increasingly used by researchers to develop potential mitigation scenarios for different emission pathways in order to guide policy-making. These prospective models integrate representations of human systems (e.g. techno-economic models) and physical processes associated with climate change and/or other environmental impacts (e.g. carbon cycle, water availability). Despite their limitations, integrated assessment models are very useful to help understand how possible technological or policy choices might lead to different future outcomes (Edenhofer et al. 2014). Because 4 Estimates of marginal land are uncertain due to inconsistencies in the definition. See Chapter 3 for a detailed discussion of marginal land. PREPUBLICATION COPY

116 Negative Emissions Technologies and Reliable Sequestration: A Research Agenda they capture linkages between regions through trade in energy and agricultural goods, among others, they are suitable to identify potential indirect impacts from BECCS. However, improvements are still needed to include impacts on biodiversity, ecosystem services, and water resources. Societal Impacts Energy crops compete with food crops for agricultural land available. Therefore, the use of BECCS might lead to food security issues. For instance, Powell and Lenton, 2012 show that the climate mitigation potential of BECCS highly depends on assumptions regarding future food production efficiency and proportion of meat in diets; the most pessimistic scenarios (low efficiency and high meat proportion) are leading to more warming. This competition for land leads to food price increases because food price is very inelastic, so that it must rise to ensure enough land is allocated to food production in high mitigation scenarios (Calvin et al., 2014). Such food price increase has already been observed a few years ago. Some authors identify the increase in first-generation biofuel production as the main cause for this price increase (Tangermann, 2008; World Bank, 2008). Zhang et al., 2010 also link increased ethanol production to short-run agricultural commodity prices. Crude oil prices and droughts might also influence food prices on the short-term (Ajanovic, 2011). Higher food prices reduce low-income populations’ access to food, especially in developing countries, potentially leading to malnourishment and social discord (Rosegrant, 2008). RESEARCH AGENDA Scientific and Technical Questions In developing its research agenda for BECCS, the committee was guided by the following questions: ● What are the limits to biomass resource potential as a carbon negative approach when considering secondary impacts such as food security, competition for water and land use, albedo changes, and biodiversity? ● Can a sufficiently diverse biomass feedstock supply chain for biomass-to-power be developed to allow for the conversion of existing coal-fired power plants to biomass (1 GW-scale)? ● Is it worth investing in biomass-to-power considering that it would take more than 1Gt dry biomass (~ 15 EJ primary energy) to replace coal in the United States (~ 17 EJ primary energy) alone? ● How does biochar soil amendment affect agricultural productivity, water use, and albedo? And, what is the carbon sequestration limit, if any, for biochar soil amendment? ● What are the techno-economic implications of optimizing current biomass-to-fuel processes for net carbon removal? Definitions The proposed BECCS research agenda uses definitions adapted from U.S. Department of Energy’s Clean Coal Program (NETL, 2015) for technology readiness levels (TRLs), bench-scale, pilot- scale, and demonstration-scale, provided in Table 4.7. These definitions assume a commercial-scale biomass-to-power or fuel plants have a dry biomass capacity of about 1000 t/d, roughly equivalent to a fuel heating value of 220 MW at 19 GJ/t dry biomass. PREPUBLICATION COPY

Bioenergy with Carbon Capture and Sequestration 117 TABLE 4.7. Bioenergy with carbon capture (BECCS) technology readiness levels (TRLs), definitions, and descriptions based on U.S. Department of Energy (DOE) definitions. (Adapted from NETL, 2015). TRL DOE Definition BECCS Description 1 Basic principles observed Lowest level of technology readiness. Scientific research begins to be and reported translated into applied R&D. Examples include paper studies of a technology’s basic properties. Applied Research 2 Technology concept and/or Invention begins. Once basic principles are observed, practical applications application formulated can be invented. Applications are speculative and there may be no proof or detailed analysis to support the assumptions. Examples are still limited to analytic studies. 3 Analytical and Active R&D is initiated. This includes analytical and laboratory-scale experimental critical studies to physically validate the analytical predictions of separate elements function and/or of the technology (e.g., individual technology components have undergone characteristic proof of laboratory-scale testing). concept 4 Component and/or system A bench-scale components and/or system has been developed and validated validation in a laboratory in the laboratory environment. Bench-scale prototype is defined as less than environment 1% of final scale (e.g.; technology has undergone bench-scale testing with biomass feed stock/simulated feedstock of 0.1-1 t/d) 5 Laboratory-scale similar- The basic technological components are integrated so that the bench-scale Development system validation in a system configuration is similar to the final application in almost all respects. relevant environment Bench-scale prototype is defined as less than 1% of final scale (e.g.; complete technology has undergone bench-scale testing using actual dry biomass feed stock of 0.01-1 t/d). 6 Engineering/pilot-scale Engineering-scale models or prototypes are tested in a relevant prototypical system environment. Pilot-scale prototype is defined as being 1-5% percent final demonstrated in a relevant scale (e.g., complete technology has undergone small pilot-scale testing environment using actual dry biomass at a scale of approximately 10-50 t/d). 7 System prototype This represents a major step up from TRL 6, requiring demonstration of an demonstrated in a plant actual system prototype in a relevant environment. Final design is virtually environment complete. Demonstration-scale prototype is defined as 5–25% of final scale or design and development of a 50-250 t/d dry biomass plant (e.g., complete technology has undergone large pilot-scale testing using dry biomass feedstock at a scale equivalent to approximately 50-250 t/d). 8 Actual system completed The technology has been proven to work in its final form and under and qualified through test expected conditions. In almost all cases, this TRL represents the end of true Demonstration and demonstration in a system development. Examples include startup, testing, and evaluation of plant environment the system within a 50-250 t/d dry biomass capacity plant (e.g., complete and fully integrated technology has been initiated at full-scale dem- onstration including startup, testing, and evaluation of using dry biomass feedstock at a scale equivalent to approximately 50 t/d dry or greater). 9 Actual system operated The technology is in its final form and operated under the full range of over the full range of operating conditions. The scale of this technology is expected to be 50-250 expected conditions t/d dry biomass capacity plant (e.g., complete and fully integrated technology has undergone full-scale demonstration testing using dry biomass feedstock at a scale equivalent to approximately 50 t/d dry or greater). PREPUBLICATION COPY

118 Negative Emissions Technologies and Reliable Sequestration: A Research Agenda Components and Tasks The Committee recommends a research agenda to advance BECCS technology with four main components: (1) crosscutting activities, (2) biomass-to-power with carbon capture, (3) biomass-to-fuel with biochar, and (4) biomass-to-fuel with carbon capture. A summary of these research components, specific tasks, and estimated budget is provided in Table 4.8 and detailed descriptions below. TABLE 4.8. Bioenergy with carbon capture research agenda, budget, and budget justification. Budget Components and Tasks TRL Duration (y) Budget Justification ($MM/y) 1. Crosscutting Activities 1.1 Regional Life Cycle Assessments and Integrated Assessment Modeling Model Development 1-3 1.5-5.0 10 0.5-1.0 $MM per project, 3-5 projects/y, 1-3 y projects Secondary Impacts 1-3 0.6-2.5 10 0.5-1.0 $MM per project, 2-3 projects/y, 1-3 y projects Spatial and Temporal 1-3 0.6-2.5 10 0.5-1.0 $MM per project, 2-3 Resolution projects/y, 1-3 y projects Food Security Impacts 1-3 0.5-2.0 10 0.5-1.0 $MM per project, 2-3 projects/y, 1-3 y projects Technology Assessments 1-3 0.5-2.0 10 0.5-1.0 $MM per project, 2-3 projects/y, 1-3 y projects 2. Biomass-to-Power with Carbon Capture 2.1 Biomass Supply and Logistics Pretreatment Technology 1-3 1.2-3.5 5 0.2-0.5 $MM per project, 6-7 projects per year, 1-2 years per project Feedstock Logistics Research 1-3 0.8-2.5 5 0.2-0.5 $MM per project, 4-5 projects per year, 1-2 years per project Bench-Scale Prototypes 4-5 2.0-5.0 5 0.5-1.0 $MM per project, bench-scale <1 t/d biomass, 4-5 projects per year, 1- 2 y projects Feasibility Study (Stage-Gate) 5|6 0.2-0.3 5 rule-of-thumb: 1% est. plant capex (100 t/d ~ 5 $MM), 0.05 $MM each, 4-5 studies/y Pilot-Scale Prototypes 6 6.0-12 5 2.0-3.0 $MM per project, pilot-scale ~ 10 t/d biomass, 3-4 projects per year, 1- 2 y projects Pilot Testing Facility 6 2.0-2.5 5 500k $/FTE, 4-5 FTE per facility, 1 facility, 5 y operation Engineering Study (Stage-Gate) 6|7 3.7-8.8 1 2% of depot-level demo project, at 1000-2000 t/d, 100-120 $/t, 5 y, 180- 440 $MM per project PREPUBLICATION COPY

Bioenergy with Carbon Capture and Sequestration 119 Budget Components and Tasks TRL Duration (y) Budget Justification ($MM/y) Depot-Level Demonstration 7-9 37-88 5 budget to be revised from engineering study, 180-440 $MM per project, 5-y project 2.2 High Efficiency Biomass Power Efficient Biomass Power 1-3 1.0-7.0 10 0.2-1.0 $MM per project, 5-7 projects Concepts per year, 1-3 years per project, 1-3 y projects Bench-Scale Prototypes 4-5 3.0-10 10 1-2 $MM per project, <1 t/d biomass, 3-5 projects/y, 1-3 y projects Feasibility Study (Stage-Gate) 5|6 1.0-3.0 10 rule-of-thumb: 1% est. plant capex (100 $MM), 1 $MM each, 1-3 studies. 1-3 y projects Pilot-Scale Prototypes 6 10-15 7 5-7 $MM per pilot-scale plant, ~10 t/d biomass, 2-3 projects per year, 1-3 y projects Pilot Testing Facility 6 2.0-2.5 7 500k $/FTE, 4-5 FTE per facility, 1 facility Engineering Study (Stage-Gate) 6|7 2.0-6.0 5 rule-of-thumb: 2% est. plant capex (100 $MM), 2 $MM each, 1-3 studies Demonstration-Scale Prototypes 7-9 20-50 5 20-25 $MM per demo-scale plant, ~100 t/d biomass, 1-2 projects a year, 1-3 y projects 3. Biomass-to-Fuel with Biochar Biochar Soil Amendments 1-3 0.4-3.0 10 0.2-1.0 $MM per project, 2-3 projects per year, 1-3 y projects Carbon Negative Pathways 1-3 1.0-7.0 10 0.2-1.0 $MM per project, 5-7 projects per year, 1-3 y projects Bench-Scale Prototypes 4-5 3.0-10 10 1-2 $MM per project, <1 t/d biomass, 3-5 projects per year, 1-3 y projects Feasibility Study (Stage-Gate) 5|6 1.0-3.0 10 rule-of-thumb: 1% est. plant capex (100 $MM), 1 $MM each, 1-3 studies. 1-3 y projects Pilot-Scale Prototypes 6 10-21 10 5-7 $MM per pilot-scale plant, ~10 t/d biomass, 2-3 projects per year, 1-3 y projects Pilot Testing Facility 6 2.0-2.5 10 500k $/FTE, 4-5 FTE per facility, 1 facility, 10 y operation Engineering Study (Stage-Gate) 6|7 2.0-6.0 5 rule-of-thumb: 2% est. plant capex (100 $MM), 2 $MM each, 1-3 studies Demonstration-Scale Prototypes 7-9 20-50 10 20-25 $MM per demo-scale plant, ~100 t/d biomass, 1-2 projects a year, 1-3 y projects PREPUBLICATION COPY

120 Negative Emissions Technologies and Reliable Sequestration: A Research Agenda TABLE 4.8 Continued Components and Tasks TRL Budget Duration (y) Budget Justification ($MM/y) 4. Biomass-to-Fuel with Carbon Capture Carbon Negative Pathways 1-3 4.2-6.0 10 0.2-1.0 $MM per project, 7-10 projects per year, 1-3 years per project, 1-3 y projects Component 1. Crosscutting Activities Task 1.1 Regional life cycle assessments and integrated Assessment Modeling The life-cycle assessment methodology is a mature tool available to determine the climate change mitigation potential of BECCS approaches in different contexts. It can therefore be used to estimate the total amount of CO2 that could be removed from the atmosphere using BECCS in the U.S. However, greenhouse gas emissions associated with indirect land use change and other potential indirect effects from competition between uses for biomass and land may occur. Integrated assessment models allow for the consideration of these indirect greenhouse gas emissions, as they combine economic and physical models within a coupled framework. However, improvements are still needed. Reducing uncertainty in the outcomes is crucial to increase the robustness of decisions that use these models as inputs (Popp et al., 2014). More sensitivity analyses should be made in order to understand the implications of various parameters and assumptions. Other carbon dioxide removal approaches such as direct air capture, biochar, or soil carbon sequestration should be incorporated to account for the full portfolio of potential solutions and improve our understanding of how BECCS and other land use based mitigation interact in different economic and political contexts (Popp et al., 2014). Most integrated assessment models also miss important elements such as impacts on ecosystem services, water resources, and biodiversity. Indeed, increasing bioenergy production is likely to lead to losses in ecosystem services and biodiversity, radiative impacts from albedo changes, and water resources depletion (Calvin et al., 2014). There is a need to better represent these secondary impacts in integrated assessment models. Finer scale modeling may be required to better consider the effect of more local parameters. IAM’s should also be updated to reflect the most recent understanding of the responses of consumers to demand-side incentives to reduce meat consumption and waste (Griscom et al., 2017 Stehfest et al. 2009, Clark and Tilman 2017), Poore an Nemecek 2018). The committee recognizes the need for additional social sciences research on reducing meat consumption and food waste, but also that there is already substantial work on these topics motivated by health and economic concerns. Finally, there is a need to improve our understanding of social consequences such as the effect of food prices increase on food security. This research program should be performed by academic researchers and national laboratories due to the large-scale, integrated analyses required and the relevant work that is ongoing in these institutions. National laboratories should be engaged to develop and curate publicly-accessible integrated assessment model platforms that can be leveraged by academic researchers and to coordinate international integrated assessment modeling efforts. This program would fall within existing research portfolios at the USDA, DOE, and EPA and a coordinated, cross-agency effort to develop integrated assessment models is recommended. Model Development The objective of this activity is to improve the robustness of integrated assessment models including other carbon dioxide removal approaches and to get better estimates of critical parameters. Competition among different uses of land is likely to accelerate as global population increases along with demand for food, fiber, and other ecosystem services such as biodiversity. Of particular concern for PREPUBLICATION COPY

Bioenergy with Carbon Capture and Sequestration 121 BECCS deployment will be competition for the land needed to produce biomass for bioenergy and the same land needed for other carbon dioxide removal approaches such as afforestation. Integrated assessment models are well suited for analyzing how land use decisions at an aggregate scale are influenced by prices for different commodities as well as policies that affect food, fiber, and bioenergy production; however, some of these demand-driven price factors may not be well represented in current models. Research is needed to improve the estimation of critical parameters such as biomass yields in integrated assessment models and to include other carbon dioxide removal approaches to account for the full portfolio of potential climate mitigation techniques while developing future scenarios. Secondary Impacts Improve integrated assessment modeling of bioenergy technology deployment impacts on ecosystem services, biodiversity, albedo changes, and water resources. Large-scale bioenergy production might result in negative effects on non-climate sustainability issues. A multi-criteria analysis has shown potential trade-offs between different sustainability issues and possible mitigation solutions (Humpenöder et al., 2018). However, research is still needed to better estimate and quantify these potential environmental impacts. For instance, water availability for energy crops remains an area of research. Improved geo-hydrological models and analysis at the regional level are needed to better understand constraints and potential solutions regarding impacts on water (Slade et al., 2014). Research is also needed to better understand impacts of biomass production for bioenergy on ecosystem services, biodiversity, and albedo changes, and then to integrate this knowledge in integrated assessment models. The recommended research should be performed by academic researchers and national laboratories. Such research is currently ongoing in universities, and additional support should be provided to accelerate knowledge development. Spatial and Temporal Resolution The objective of this activity is to create integrated assessment models with higher spatial and temporal resolution. Most integrated assessment models function at a global scale and therefore represent average conditions and system responses that probably do not accurately represent actual conditions and system responses at scales needed for effective policy and decision-making. As a result, it is necessary to explore ways to nest or link smaller scale models within global-scale models (similar to what has been done with global climate models) that can be tailored to more local circumstances, but still function adequately within the larger global context. Food Security Impacts The objective of this activity is to improve our understanding of the impact of BECCS technology deployment on food prices and food security. The large-scale implementation of land-based carbon dioxide removal solutions might lead to food prices increase through competition for land, as has been shown in some studies (Kreidenweis et al., 2016; Smith et al., 2013). However, if extra land needed is already available or if biomass feedstock does not compete with agricultural land, food price increases may not be that high (Lotze-Campen et al. 2014), and mitigation measures can be implemented to limit impacts on food security (Smith et al. 2013). Integrated assessment models estimate food prices increase caused by large-scale bioenergy production. However, uncertainties are still high and potential impacts on food security issues (e.g. malnutrition, food riots) are not yet well understood. Research is needed to better understand these impacts and to develop policy guidelines for the implementation of potential mitigation measures. Research is also needed to design appropriate safeguards to ensure food security. A good deal of social scientific and policy-focused research has already been undertaken on the general safeguards required to ensure food security in the face of large-scale land use change. This work needs to be reinterpreted and revised for the special case of BECCS. PREPUBLICATION COPY

122 Negative Emissions Technologies and Reliable Sequestration: A Research Agenda Technology Assessments Few life-cycle assessment studies have been published to assess potential environmental impacts associated with carbon dioxide removal technologies. Life-cycle assessment methodology relies heavily on available data, models, and assumptions to quantify CO2 life-cycle emissions. It is therefore critical to follow similar methodological rules when comparing life-cycle assessment results to ensure valid conclusions. Product category rules allow consistency and comparability of results by providing product or sector-specific guidance. There is a need to develop such consensual life-cycle assessment guidelines specific to biomass energy carbon dioxide removal technologies in the United States. Component 2. Biomass-to-Power with Carbon Capture The research agenda for biomass-to-power with carbon capture has two main elements: (1) biomass pretreatment and logistics for the conversion of conventional pulverized coal power plants to biomass, and (2) high efficiency biomass power generation. Pretreated biomass feedstocks for operation in conventional coal-plants will, in the near-term, leverage worldwide fixed-capital coal power plant investments, while creating a biomass fuel supply logistics infrastructure for supporting future, more efficient biomass power generation. In the long-term, high efficiency biomass power generation, will be essential for carbon negative biomass-to-power to be sustainable, scalable, and cost-effective. Task 2.1 Biomass Supply and Logistics The development of a robust biomass feedstock supply and effective supply chain logistics is key to replacing today’s coal power plants with biomass fuel. This research task aims to establish a coal- compatible biomass feedstock depot capable of delivering enough fuel to completely convert a coal power plant to biomass. The program has two main research thrusts: (1) pretreatment technology for converting biomass into a drop-in replacement for coal and (2) logistics research to address biomass supply chain issues (production, storage, handling, and transportation). This research program will need to leverage the nation’s entire innovation ecosystem, from academia to private industry. Both the agricultural and electric power industries will need to be engaged early in this program. Applied research and bench-scale prototype development of pretreatment technology and logistics research would be carried-out by university researchers, national laboratories, and R&D organizations. Pilot and demonstration-scale development need to leverage public-private partnerships, with private industry and start-up companies taking the lead and supported by national laboratories. In particular, national laboratories would be needed to operate pilot-scale testing facilities. Program managers would have to contract with third-party engineering design and estimation firms to provide engineering and economic assessments of technologies under consideration for scale-up (stage- gate). The management and operation of the final biomass demonstration depot project would need to be a public-private partnership, preferably hosted by a large utility with coal power generation assets. This program would fit within research portfolios and funding priorities of the DOE and USDA and governance of these projects can be conducted following the guidelines of these departments. Pretreatment Technology The objective of this activity is to identify optimal biomass densification, pretreatment, and formation techniques that convert a variety of biomass feedstocks into a standardized drop-in replace for coal. Research is needed to evaluate and develop biomass densification, pretreatment, and formation techniques using variety of biomass feedstocks (agricultural byproducts, energy crops, wood, and organic waste) into a product that is compatible with coal-fired power plants. Promising technologies should be promoted from applied research to bench-scale prototypes (< 1 t/d biomass) and pilot-scale prototypes (10 t/d biomass). Process designs should be aimed at modualarized solutions with dry biomass capacity of about 100 t/d to enabled a distributed pretreated biomass supply chain. PREPUBLICATION COPY

Bioenergy with Carbon Capture and Sequestration 123 Feedstock Logistics Research The objective of this activity is to determine the supply chain logistics requirements (sources, collection, processing, storage, and transporation) to deliver pretreated biomass fuel to U.S. coal power plants with the aim of creating a national pretreated biomass demonstration depot capable of supplying enough biomass to convert a conventional coal power plant to biomass. Research projects are needed to evaluate the biomass supply chain logistics required to supply an existing U.S. coal power plant under 20- years old with pretreated biomass. The proposed research is distinct from the current feedstock supply and logistics research at DOE (BETO, 2017), in that the objective is to pretreat biomass at or near production; i.e. distributed biomass pretreatment. Consideration should be given to availability of geological CO2 sequestration for implimenting biomass-to-power with carbon capture and sequestration. Logistics research will need to include biomass production, waste resources, collection, processing, and transportations and include carbon life-cycle assessments, supply chain economics, and barriers to implimentation. Task 2.2 High Efficiency Biomass Power The fundamental challenge for biomass-to-power conversion efficiency is the relatively low fire- side boiler temperature in a conventional biomass power plant, which is typically well below 700°C. At these temperatures, the technology options for thermal-to-electric conversion are limited to conventional steam turbines (Rankine cycle) with efficiencies below 40%. Thus, research is needed to develop technology that convert biomass-to-heat and produce working fluid temperatures over 1100°C and/or biomass-to-power with conversion efficiencies over 60%. Some possible, but not exhaustive transformational research directions include: (1) liquid phase (molten glass or salt) combustion; (2) chemical looping combustion; 3) novel reactor designs that are process intensified and leverage additive manufacturing; (4) new high temperature, corrosion resistant materials and materials processing; (5) high efficiency heat exchanger designs that are process intensified and leverage additive manufacturing; (6) gasification pathways; (7) liquification and liquid combustion pathways; (8) in situ high temperature gas clean-up; (9) enabling biomass pretreatment processes; and (10) small-scale, modular power generation concepts. This research program will need to leverage the nation’s entire innovation ecosystem, from academia to private industry. Applied research and bench-scale prototype development of high efficiency biomass-to-power concepts should be carried-out by university researchers, national laboratories, and R&D organizations. Pilot and demonstration-scale development should be led by private industry and start-up companies with support from universities, national laboratories, and R&D organizations. In particular, national laboratories should be engaged to operate pilot-scale testing facilities. Program managers should contract third-party engineering design and estimation firms to provide engineering and economic assessments of technologies under consideration for scale-up (stage-gates). This program would fit within the research portfolios and funding priorities of the DOE. The DOE Office of Fossil Energy’s National Energy Technology Laboratory (NETL) has the most relevant expertise and experience for managing this program due to their long history developing coal power plant technology, advance power generation, and carbon capture technology—even though biomass power does not exactly fall within the priorities of Fossil Energy. Component 3. Biomass-to-Fuel with Biochar Biomass-to-fuel with biochar processes hold tremendous promise as a cost-effective, carbon negative pathway. Despite some recent high-profile failures to commercialize thermochemical biomass- to-fuels technology (Fehrenbacher, 2015), promising new biomass-to-fuel processes continue to emerge. PREPUBLICATION COPY

124 Negative Emissions Technologies and Reliable Sequestration: A Research Agenda For example, a recent technoeconomic analysis of a fast pyrolysis with hydrotreating process suggests this technology can make a gasoline/diesel blendstock with a minimum fuel selling price of $29/GJ (3.46 $/gge) from 88 $/t dry wood and with negative carbon emissions of -3 kg/GJ CO2 per fuel produced (NREL, 2015). Another example is a new integrated hydropyrolysis with hydrotreating process (IH2) that makes drop-in gasoline and diesel fuels with a projected a minimum fuel selling price of $14/GJ (1.68 $/gge) from 79 $/t dry wood and negative carbon emissions of -0.89 kg/GJ CO2 per fuel produced (Maleche et al., 2014; Tan et al., 2014). While these technologies still have net positive life-cycle greenhouse gas emissions, the processes themselves can be carbon negative. The Carbon negative biomass-to-fuel with biochar processes can be advanced by determining the value of co-produced biochar and by optimizing existing processes or developing new pathways that maximize carbon removal. To this end, research in two main areas is proposed. First, biochar permanence in soil and impact on crop productivity needs better quantification to determine its long-term value as a soil amendment and viability for carbon sequestration. Second, carbon negative biomass-to-fuel conversion pathways need to be developed that are ideally both profitable from fuel production and carbon negative through the co-production of large quantities of sequestered biochar. This research program will need to leverage the nation’s entire innovation ecosystem, from academia to private industry. Applied research and bench-scale prototype development of carbon negative biomass-to-fuel processes and enabling subsystems should be carried-out by university researchers, national laboratories, and R&D organizations. Pilot and demonstration-scale development should be led by private industry and start-up companies with support from universities, national laboratories, and R&D organizations. National laboratories should be engaged to operate pilot-scale testing facilities. Program managers should contract third-party engineering design and estimation firms to provide engineering and economic assessments of technologies under consideration for scale-up (stage-gates). This program would fit within the research portfolios and funding priorities of the DOE and USDA. Biochar Soil Amendments Quantitative assessments are needed of how biochar soil amendments effects agricultural productivity, water use, and albedo. Additionally, the carbon sequestration limit and permanence of biochar as a soil amendment needs to be assessed to accurately quantify the carbon storage potential of this technology. Since biochar composition and structure depends upon the biomass feedstock and process by which it is produced, quantitative assessments should be coupled with promising biomass-to- fuel conversion processes. Carbon Negative Pathways A range of thermochemical conversion pathways for converting biomass to fuels have been developed; including gasification, pyrolysis, hydropyrolysis, hydrothermal liquefaction, and others. Currently, none of these pathways have net negative life-cycle carbon emissions; however, most technology developers optimize processes for maximum fuel production, not carbon emissions—often burning co-produced biochar to provide low-cost process heat. Research is needed aimed at optimizing existing biomass-to-fuel processes and developing new pathways for net carbon negative emissions. Emphasis should be on robust processes and that can utilize a multitude of biomass feedstocks to maximize their long-term commercialization potential as well as enabling subsystem technologies that reduce the overall costs of carbon negative biomass-to-fuel processes. Component 4. Biomass-to-Fuel with Carbon Capture Carbon Negative Pathways At the time this study, biological pathways for converting lignocellulosic biomass-to-fuels appears to be the most speculative carbon removal approach. The fundamental problem is the recalcitrance of lignin and the inability of organisms to metabolize it. Consequently, most integrated PREPUBLICATION COPY

Bioenergy with Carbon Capture and Sequestration 125 lignocellulosic biorefineries burn their lignin for process heat and power. Since lignin constitutes about 30% of the weight and 40% of the energy content of all biomass, burning it severely limits the potential for a scalable carbon negative process. Nonetheless, the merits of producing a pure CO2 stream during fermentation that can be easily captured and stored is sufficient motivation to warrant basic and applied research into net carbon negative biological pathways. Specifically, bioengineering research aimed at designing pathways to breakdown lignin and convert it into fuels should be investigated. Successful biological lignin valorization could completely transform the economics of biological biomass-to-fuel processes and their potential for carbon removal. Therefore, an ongoing applied research program to develop carbon negative biological conversion of lignocellulosic biomass into fuel, conducted at universities and national laboratories, and managed by the DOE is recommended. Future Research Considerations If BECCS technology is to be deployed at scale, additional research considerations will arise in its future implementation. Specifically, an efficient and coordinated supply and utilization system will be needed. These systems-level needs identified by the committee include: ● Spatially-explicit optimization of biomass-to-fuel and power implementation to design optimal BECCS network configuration accounting for plant scale, location relative to biomass supply, competition for biomass supply, CO2 transport network and CO2 and/or char sequestration sites is needed. ● Integration of biomass power plants with an electricity grid that may have a high fraction of various renewable energy technologies (e.g. solar, wind, etc.) in the future will present challenges in terms of load following, requiring improved understanding and control over ramping and flexibility. ● Reductions in the capital cost and energy consumption of carbon capture and sequestration are needed to improve economic and technical viability of BECCS, with particular attention paid to any challenges that biomass feedstocks may introduce for carbon capture and sequestration. ● The quality and variability of CO2 produced from biomass power plants and the impacts on carbon capture system components will need to be analyzed to understand long-term impacts on pipeline, well-head, and subsurface equipment. ● Coherent policy and governance, such as emissions accounting when biomass supply is not collocated with consumption (e.g. different countries) is needed to promote biomass markets, and extension and outreach may be needed to encourage landowners to adjust crops and practices. Implementation of the Research Agenda Funding Scale of Funding The research agenda budgets for prototype development were estimated assuming a 1000 t/d dry biomass commercial-scale plant has a capital cost of about $100 million, which for a 50% efficient power plant corresponds to capital cost of about $900/kW electrical capacity—on par with the cost of natural gas combined cycle power plants. Then using the “2/3 law” for economies of unit scale: = where k is the plant capital cost ($), c is the plant capacity (t/d), c0 is the reference unit capacity, and α is the scaling factor of 2/3; an order-of-magnitude cost was estimated for bench, pilot, and demonstration- scale prototypes, Table 4.9. PREPUBLICATION COPY

126 Negative Emissions Technologies and Reliable Sequestration: A Research Agenda TABLE 4.9. Estimated bench, pilot, demonstration-scale plant costs, dry biomass capacities, and technology readiness levels. Plant Scale Bench Pilot Demonstration Commercial Technology Readiness Level 4-5 6 7-9 10+ Dry Biomass Capacity, t·d-1 1 10 100 1000 Fuel Power, MW 0.2 2.2 22 220 Capital Cost, $MM 1 5 22 100 Cost per Capacity, $MM/(t·d-1) 1 0.5 0.2 0.1 Sequencing of Funding The research agenda budgets for bioenergy with carbon capture technology development are intended to be staggered over a period of 15 years. This approach is intended to reduce technology and financial risk. Figure 4.10 provides an example of this sequence of research funding for each of the three BECCS pathways for the research agenda. FIGURE 4.10. Illustrative research agenda budgets per year showing possible sequencing for biomass-to-power with carbon capture (top), biomass-to-fuel with biochar (middle), and biomass-to-fuel with carbon capture (bottom) pathways. PREPUBLICATION COPY

Bioenergy with Carbon Capture and Sequestration 127 Sources of Funding Though not explicitly called out in the research agenda, it is generally assumed that most of the funding is coming from the government. That said, for more mature technology development projects it would not be unreasonable to expect industry participants to provide some or even all project funding. While the details of how this research agenda should be funded is outside the scope this study, mechanisms other than traditional federal instruments for funding research and development, such as market-based policy incentives, could be worth exploring. Institutional Structures The U.S. government currently has several agencies engaged in and capable of effectively carrying out most of the proposed basic and applied research components and tasks, the most active being within the U.S. Department of Agriculture (USDA), Department of Energy (DOE), and Environmental Protection Agency (EPA). While these agencies have programs well-suited to carrying out basic and applied research, it is not clear they are currently equipped to effectively run a technology demonstration program. In the past, public-private partnership entities have played a critical role in the demonstration and deployment of new technology. For example, two such organization were the Electric Power Research Institute (EPRI) and the Gas Research Institute (GRI) that received their funds from taxes on interstate transmissions (electricity and gas) until utilities deregulation phased out this funding mechanism in the 1990s. In the absence of such organizations, Deutch, 2011 proposed the creation of a new institution that would be responsible for managing and selecting technology demonstration projects that is supported by, but separate from the U.S. Government that he called “the Energy Technology Corporation”. This organization would house a well-designed technology demonstration program with the appropriate authority, tools, and expertise to accelerate technology development. The evaluation of existing government agency technology demonstration capabilities and the investigation of institutional structures that will have the necessary capabilities required to effectively develop and demonstrate new biomass energy technology is necessary to ensure success of scale-up and deployment of new technologies. Research Management The governance of a technology development program that includes demonstrating pilot prototype systems require engineers with industrial experience as well as the development of standards for managing and evaluating new processes. The most recent example where this has been done by the government is the Carbon Capture and Sequestration (CCS) Program5 run by the National Energy Technology Laboratory (NETL). NETL developed a standard methodology for assessing the cost of carbon capture from coal power plants and corresponding impacts on electricity costs. In addition, they developed a comprehensive technology development roadmap that spanned from basic research to demonstration-scale plants. The development of pilot and demonstration-scale process evaluation standards is essential for the effective governance of biomass energy technology development. These standards include process design engineering, equipment costing, and techno-economic analysis. Once a standard design basis has been developed, the use of third-party, independent, for-profit process engineering and estimating firms to provide technology assessments and techno-economic analyses is the most cost-effective way to vet new 5 See https://www.netl.doe.gov/research/coal/carbon-capture/carbon-capture-program. PREPUBLICATION COPY

128 Negative Emissions Technologies and Reliable Sequestration: A Research Agenda biomass energy processes. It is important that these technology evaluations are made available to the public and how results were obtained is transparent. Carbon Accounting and Monitoring One practical implementation challenge for any carbon removal technology is the accounting and crediting for carbon removal. By contrast, CO2 emissions from the combustion of fossil fuels is straightforward and easily accounted for using existing reporting on fossil fuel extraction, imports, and sales. For biomass energy carbon removal approaches, carbon accounting is particularly challenging as the amount of net carbon removal is highly dependent on the specific pathway chosen (production, transport, conversion, sequestration). Policy research may be necessary to assess methods that could provide a simple and fair system to track net carbon removal. Monitoring the impacts of increasing biofuel production on land area and leakage, as well as CO2 accumulation rates on land used for biofuel, are essential aspects of program implementation. Research needs that build on existing land monitoring programs are covered in the land chapter. Likewise, there is a need to consider monitoring the leakage of sequestered carbon gases from CCS, which is covered in the Geologic Sequestration chapter. SUMMARY Developing and deploying carbon negative bioenergy technology that is sustainable, scalable, and commercially viable is a daunting task with many possible approaches, each with their own unique benefits and challenges. A research agenda that attempts to group and prioritize the most promising of these approaches and put forth a realistic path for researching, developing, demonstrating, and deploying commercial BECCS technology is recommended. This research agenda has four components: (1) integrated assessment modelling; (2) biomass-to-power with carbon capture; (3) biomass-to-fuel with biochar; and (4) biomass-to-fuel with carbon capture. Biomass supply is the overarching concern and consideration for large-scale implementation of BECCS technology. Worldwide, full-scale BECCS deployment will require addition 300-600 Mha of land (roughly equal to the area of Australia) for energy crops. In the United States, assuming a billion tons of biomass is needed, a sufficient supply could be achieved with energy crops, forest biomass, organic waste, and agricultural residues, but the associated greenhouse gas emissions and environmental impacts are still unclear. To accurately assess the impact of BECCS on net greenhouse gas concentrations and climate change, a model is needed that includes the following essential elements: (1) land use change impacts, including long-term nutrient and productivity changes; (2) biomass harvesting, processing, and transportation related emissions (supply-chain emissions); (3) combustion efficiencies and related emissions of different fuels (referred to as “fuel substitution”); (4) indirect impacts, such as changes in land use or reductions in timber product inventories due to increased biomass demand; and (5) carbon capture, transport, and storage related emissions. In addition, the changes in albedo and other biophysical processes that alter how greenhouse gases affect the climate should be factored. Currently, no such comprehensive integrated assessment model exists. To accurately assess how BECCS impact greenhouse gas concentrations and climate change, research is required to build a holist integrated assessment platform that incorporates the essential elements above, as well as albedo and other climate impacts. Today’s biomass-to-power plants suffer from being unable to sustain a consistent biomass supply, price, and composition and from low power plant efficiency, which present barriers to the deployment of carbon negative biomass-to-power with carbon capture. Therefore, the biomass-to-power with carbon capture research agenda focuses on (1) biomass supply and logistics through conversion of conventional pulverized coal power plants to pretreated biomass fuel; (2) next generation high efficiency biomass power generation. In the near-term, the development pretreated biomass as a drop-in replacement for coal in conventional coal-fired power plants will leverage existing fixed-capital investments (coal power plants), while creating a robust, distributed biomass fuel supply logistics infrastructure able to support PREPUBLICATION COPY

Bioenergy with Carbon Capture and Sequestration 129 future, more efficient biomass power generators. In the long-term, it is essential for biomass-to-power conversion to have higher efficiency for this carbon removal approach to be cost-effective, sustainable, and impactful. To accelerate technology deployment, this research agenda calls for the development of bench, pilot, and demonstration-scale prototypes of the most promising biomass pretreatment and biomass-to-power conversion technologies. Biochar is one of the most promising near-term commercially viable carbon removal approaches. However, emerging commercial thermochemical biomass-to-fuel with biochar processes seek to either maximize the production of liquid fuel and minimize biochar or maximize biochar production for sale into niche, high-end, home garden markets and minimizing liquids. Several thermochemical processes approaches have the potential to be commercially viable without a price on carbon and have net negative carbon emissions, but not at not at the same time. However, if the economics of biochar co-production could be positively changed by definitively demonstrating that biochar soil amendments can increase crop yields—it would allow technology developers to co-optimize for both fuel and biochar, potentially making their process net carbon negative. As such, one of the research agenda aims is to quantify biochar permanence in soil and impact on crop productivity. The research agenda also aims to optimize existing biomass-to-fuel processes for carbon removal and investigate completely new carbon negative pathways. To accelerate technology deployment, the research agenda calls for the development of bench, pilot, and demonstration-scale prototypes for the most promising carbon negative approaches, scaling the process dry biomass capacity from roughly 1 t/d bench-scale to 100 t/d demonstration-scale. Biomass-to-fuel with carbon capture (or biological conversion) pathways are the last potentially carbon negative biomass technology considered in this chapter (see Figure 4.1). However, biological conversion pathways were determined to have a low potential for being carbon negative because the microorganisms currently used are unable to effectively decompose lignin. In integrated biorefineries, lignin derived from biomass is typically burned for heat and power. Given that lignin represents about 30% by mass and 40% by energy content of all biomass, bioengineering pathways to break down and convert lignin to liquid fuels is specifically recommended. More broadly, only basic and applied research on carbon negative pathways is recommended for biological biomass conversion until a breakthrough is made in lignin valorization. PREPUBLICATION COPY

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To achieve goals for climate and economic growth, “negative emissions technologies” (NETs) that remove and sequester carbon dioxide from the air will need to play a significant role in mitigating climate change. Unlike carbon capture and storage technologies that remove carbon dioxide emissions directly from large point sources such as coal power plants, NETs remove carbon dioxide directly from the atmosphere or enhance natural carbon sinks. Storing the carbon dioxide from NETs has the same impact on the atmosphere and climate as simultaneously preventing an equal amount of carbon dioxide from being emitted. Recent analyses found that deploying NETs may be less expensive and less disruptive than reducing some emissions, such as a substantial portion of agricultural and land-use emissions and some transportation emissions.

In 2015, the National Academies published Climate Intervention: Carbon Dioxide Removal and Reliable Sequestration, which described and initially assessed NETs and sequestration technologies. This report acknowledged the relative paucity of research on NETs and recommended development of a research agenda that covers all aspects of NETs from fundamental science to full-scale deployment. To address this need, Negative Emissions Technologies and Reliable Sequestration: A Research Agenda assesses the benefits, risks, and “sustainable scale potential” for NETs and sequestration. This report also defines the essential components of a research and development program, including its estimated costs and potential impact.

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