“This is a big deal, because we are saying the primary amount of biomass will come from energy crops that have not yet been established, have not yet had enough research and information on optimizing production yield and systems. There is a lot of work to be done to make this come true.”
“We have the land, the will, and by bringing our sciences together we can provide the way for using biomass for feedstocks and commodities in our biorefineries.”
“Initially, advanced biofuels will be produced in integrated supply chains; no one will grow new crops without an assured customer, and no one will finance or build new conversion capacity without an assured source of feedstock. Truly fungible products will be traded as commodities, but most products will also form part of an end-to-end supply chain in early applications.”
As participants in the workshop discussed, biomass utilization is an important addition to the nation’s energy economy. Bryce Stokes explained the future potential of biomass production in the United States and noted that the billion-ton goal is attainable. Biomass could potentially be used to displace about 30 percent of the petroleum consumption or produce 5 percent of the electricity used in America. Brian Duff pointed out that biomass is also very useful for transportation, as it can be processed into high-density fuels for a wide variety of vehicles. The participants in the workshop discussed in detail the challenges and opportunities for developing biomass utilization for both electricity generation and production of fuels and chemical feedstocks.
The United States has enough land and technological knowledge to produce over one billion tons of biomass per year at $60 or less per ton for use in making fuels and chemicals and generating power without impacting current uses agricultural and forestry acreage, noted Bryce Stokes, senior advisor with CNJV, a contractor to DOE.
A significant amount of that biomass will come from increased production of energy crops, with increased use of corn stover and straws also making a significant contribution to the increase, said Stokes. Brian Duff, chief engineer and acting deployment team leader for the Office of Biomass Program at DOE, said that there is also a real opportunity to make efficient use of the woody component of municipal solid waste and construction and demolition wood. However, a major challenge to utilizing these resources will be developing a cost-effective system for getting widely distributed, non-uniform biomass to fuel, chemical, and power production sites. In the meantime, research has developed a variety of biological and thermochemical schemes for turning biomass into fuels, chemicals, and energy. The list of building blocks, secondary chemicals, intermediates, and end products that can be made from biomass feedstocks is virtually limitless, just as it is with petroleum.
Bryce Stokes noted that the United States has abundant, renewable biomass resources to use for feedstocks, although the supply today and the form in which most of it exists is not sufficient to meet the 30 percent petroleum displacement goal that the nation needs for energy, chemicals, and other materials. However, he said, with the supply of land in the United States, combined with the nation’s technological prowess and its people, it should be possible to grow enough biomass to meet those needs. Moreover, it should be possible to do so within a resource management and sustainability framework that meets other social demands.
Starting with available land, Stokes explained that there are six major classes of land, drawing mainly from a 2011 report from the U.S. Department of Agriculture:1
1Nickerson, C., R. Ebel, A. Borchers, and F. Carriazo. 2011. Major Uses of Land in the United States, 2007. Economic Information Bulletin No. 89. December 2011 [online]. Available: http://www.epure.org/pdf/0w3ea6c0898164-d04c.pdf.
- Cropland, which includes all land currently used to grow crops, idle cropland, and cropland used only for pasture. Total cropland in the lower 48 states is approximately 408 million acres.2
- Grassland pasture and range, including permanent grassland and other non-forested range and pasture, totals about 612 million acres.3
- Forest-use land is total forestland as classified by the U.S. Department of Agriculture (USDA) Forest Service, excluding an estimated 80 million acres used primarily for parks, wildlife areas, and other uses. Forest-use land totals 576 million acres in the lower 48 states.4
- Special-uses land includes areas for rural transportation, recreation and wildlife, various public installations and facilities, farmsteads, and farm roads, including the 80 million acres of forested land noted above. There are approximately 169 million acres in this category.5
- Miscellaneous land includes areas in various uses not inventoried, marshes, open swamps, bare rock areas, desert, tundra, and other land generally of low agricultural value and total about 68 million acres.6
- The urban land base includes streams and canals less than an eighth of a mile wide, and ponds, lakes, and reservoirs covering less than 40 acres. This category total about 60 million acres.7
Land use is not uniform across the United States but varies according to soil type, climatic conditions, and other facts. Figure 2-1 shows the major uses of land in 2007.
Stokes discussed some of the major forest and agricultural biomass resources that could serve as feedstocks. Forest resources include logging residues, which are very inexpensive to buy, but collecting them and converting them into something that can be transported can be expensive. Forest thinnings are trees removed for fire control or health improvements and the wood is usually not sellable, so it could be used as a feedstock resource. Conventional wood, in contrast, is marketable, but Stokes said that some of this wood may be diverted for use as a feedstock resource. Fuelwood is wood that goes to the pulp and paper industry for making heat and power for their plants. It also includes a few of the electrical power plants that use wood. Finally, there are the mill residues, pulping liquors, and urban wood resides, such as waste paper and yard trimmings, that could serve as energy feedstocks, though collection is the big issue because many of these are diffuse resources.
Agricultural resources include grains that go into biofuel production, oil crops, and crop residues. Energy crops include perennial grasses, such as switchgrass, bluestem, Miscanthus, and others, and perennial wood crops, which include poplar, willow, pine, and eucalyptus, among others. Agriculture also generates animal manures and food and feed processing residues that could serve as production feedstocks, as well as municipal solid waste, landfill gases, and annual energy crops such as sorghum.
He then reviewed the 2011 update of DOE’s Billion-Ton report, for which he was a co-lead. The Billion-Ton Update examines the nation’s capacity to produce a billion dry tons of biomass resources annually in the 48 coterminous states for energy uses without impacting other vital U.S. farm and forest products, such as food, feed, and fiber crops. The study provides industry, policy makers, and the agricultural community with county-level data and includes analyses of current U.S. feedstock capacity and the potential for growth in crops and agricultural products for clean energy applications. He noted that the 2011 study, unlike the earlier 2005 study, examined both current use and potential use up to 2030, and it included methodology to examine biomass potential at the county level. The 2011 study also included the costs for getting biomass to the roadside for transport and includes scenarios based on crop yields and tillage practices as well as sustainability criteria. The report, as well as all of the data, are available at www.bioenergykdf.net.
To develop county-level projections, Stokes and his colleagues used the POLYSYS economic model developed at the University of Tennessee Agricultural Policy Analysis Center (www.agpolicy.org). This model is anchored to the USDA’s 10-year baseline projections for eight major crops, and it includes projections for biomass resources that include corn stover, straws, and energy crops. The model also incorporates USDA-projected demands for food, feed, industry, and export, and works on a land base that includes
2Nickerson, C., R. Ebel, A. Borchers, and F. Carriazo. 2011. Major Uses of Land in the United States, 2007. Economic Information Bulletin No. 89. December 2011 [online]. Available: http://www.epure.org/pdf/0w3ea6c0898164-d04c.pdf.
3Nickerson, C., R. Ebel, A. Borchers, and F. Carriazo. 2011. Major Uses of Land in the United States, 2007. Economic Information Bulletin No. 89. December 2011 [online]. Available: http://www.epure.org/pdf/0w3ea6c0898164-d04c.pdf.
4Nickerson, C., R. Ebel, A. Borchers, and F. Carriazo. 2011. Major Uses of Land in the United States, 2007. Economic Information Bulletin No. 89. December 2011 [online]. Available: http://www.epure.org/pdf/0w3ea6c0898164-d04c.pdf.
5Nickerson, C., R. Ebel, A. Borchers, and F. Carriazo. 2011. Major Uses of Land in the United States, 2007. Economic Information Bulletin No. 89. December 2011 [online]. Available: http://www.epure.org/pdf/0w3ea6c0898164-d04c.pdf.
6Nickerson, C., R. Ebel, A. Borchers, and F. Carriazo. 2011. Major Uses of Land in the United States, 2007. Economic Information Bulletin No. 89. December 2011 [online]. Available: http://www.epure.org/pdf/0w3ea6c0898164-d04c.pdf.
7Lubowski, R.N., M. Vesterby, S. Bucholtz, A. Baez, and M. Roberts. 2006. Major Uses of Land in the United States, 2002. Economic Information Bulletin No. (EIB-14) May 2006.
FIGURE 2-1 Land use summary. The first diagram shows land use for all states, and the second includes all states except Alaska and Hawaii. The land use is significantly affected by Alaska as it has a large forestry-use, special-use and miscellaneous other land areas and small cropland and pasture areas.
SOURCE: Cynthia Nickerson, Robert Ebel, Allison Borchers, and Fernando Carriazo. Economic Information Bulletin No. (EIB-89). 67 pp. December 2011. http://www.ers.usda.gov/Publications/EIB89/EIB89.pdf.
250 million acres of cropland, 22 million acres of cropland pasture, 61 million acres for hay production, and 118 million acres of permanent pasture. The update is based on the USDA baseline scenario extended to 2030 and a high-yield scenario that increases corn yields by 1 percent annually over the baseline projections and that energy crop yields increase by 2-4 percent annually as a result of a concerted research and development effort. The high-yield scenario also assumes that a larger amount of cropland will move to no-till practices that allow for greater residue removal for feedstock use within sustainability limits that prevent soil erosion and retain water and nutrients. Stokes noted that a significant amount of effort went into modeling crop residue sustainability.
The model also assumed that energy crops would only be grown on cropland, cropland pasture, and permanent pasture without irrigation and using minimum tillage practices. Energy crops also had to pay for themselves; that is, the economic return had to be greater than that from other agricultural uses. Land use was assumed to change slowly between now and 2030, though land use for energy crops will increase from 63 million acres in the baseline scenario to 79 million acres under the high-yield scenario. Stokes remarked that this is significant because the model predicts that the primary amount of biomass will come from energy crops that have not yet been established and for which there has not been enough research and information on optimizing production yield and systems.
The bottom line, said Stokes, is that current combined resources from forests and agricultural lands total about 473 million dry tons annually at $60 or less per dry ton. About 45 percent of that is currently produced and the remainder is potential additional biomass. Under both baseline and high yield scenarios, biomass resources are predicted to total from nearly 1.1 billion dry tons annually by 2030 under the baseline scenario to as much as 1.6 billion dry tons annually under the high-yield scenario. A significant amount of that biomass under both scenarios will come from
increased production of energy crops, with increased use of corn stover and straws also making a significant contribution to the increase. Very little of the increase comes from forestry because current production there is already high. Stokes made the point that woody mill residues will not contribute to increased energy production because very little primary mill residue goes unused. Waste from pulp and paper mills is already being used to make energy, he explained. There is, however, a real opportunity to make efficient use of the woody component of municipal solid waste and construction and demolition wood, with Stokes calling this combined resource a potential gold mine.
Figure 2-2 summarizes all of the data in a county-level map showing that there is the potential to have fairly well distributed access to many types of feedstocks at the $60 or less per dry ton by 2030. Stokes noted that the Billion-Ton study did not include algae as a potential feedstock—algae was the subject of a parallel study—but that it did identify 106 million acres of suitable land for algae production with the potential to produce 58 billion gallons of algal oil per year. Those figures drop to 2.4 million acres of land and 5 billion gallons of algal oil per year when only considering lands that optimize productivity and minimize water use. These maximally productive sites are clustered in the southwest and along the Gulf Coast.
The Feedstock Delivery System
Stokes then turned to the subject of raw material handling and supply systems, briefly discussing some of the different systems that are being developed and studied; see Figures 2-3 and 2-4. For example, a system to handle switchgrass produces large square bales as the switchgrass is being harvested. The resulting bales require industrial equipment to load onto trailers. Another system for switchgrass uses a field chopper and solar energy to dry the harvested grass in the field. This type of system eliminates bale handling and de-baling and increases the energy density of the final feedstock, but it does require two passes through the field, one to cut the switchgrass, the second to collect it after drying. He also described a single-pass system (Figure 2-4) for collecting corn residue that greatly increases the efficiency of collection and transport, and systems for harvesting trees and short-rotation wood crops such as willow.
It is important when developing any collection system, he said, to consider total cost, including the expense of drying materials at a refinery and labor costs. He added that a possible goal of research and development efforts could be to reduce the variability and uncertainty around feedstock quality specifications in terms of sugar content, moisture, and ash. A commodity feedstock for energy and chemical
FIGURE 2-2 Potential county-level resources at $60 per dry ton or less in 2030 under baseline assumptions.
SOURCE: 2011 U.S. Billion-Ton Update: Biomass Supply for a Bioenergy and Bioproducts Industry.
FIGURE 2-3 Bulk-format system to harvest, handle, store, and deliver low-moisture switchgrass.
SOURCE: Image taken from Stokes presentation.
FIGURE 2-4 Single-pass harvest system for corn and corn stover.
SOURCE: AGCO Corporation.
production, explained Stokes, needs to be reliably available, have uniform density and stability, and must be readily stored. As far as algae is concerned, he explained that the biggest production barrier today is that the fundamental biology of algae is poorly understood. There is active fundamental and applied research ongoing on algae as a potential source of biomass, but he noted that translating indoor lab results to outdoor production environments is not a trivial matter.
A variety of different programs are addressing research and development needs to address the grand challenges and achieve the vision of producing one billion tons of biomass annually at a cost of $60 or less per ton. A joint USDA-DOE program, for example, is focusing on genomics-based research that will lead to the improved use of biomass and plant feedstocks for the production of fuels. This five-year, $40.1 million effort focuses on a range of plants, including rice, switchgrass, sorghum, and poplar, among others. The private sector is involved, as well, developing high-biomass dedicated energy crops with increased nitrogen use efficiency. Stokes noted one effort, the Knowledge Discovery Framework supported by DOE, that will serve as a biomass research and development resource library into which the large network of institutions in the Regional Biomass Feedstock Partnership will deposit data annually.
The Uniform Commodity Feedstock Vision
The bottom line, said Stokes, is that there needs to be a transition from picking up materials with inefficient systems and just chopping it up or baling it and hauling it to the biorefinery. This approach, he said, is not meeting quality specs, is not integrating well into biorefineries, and is wasting money. Instead of trying to feed biomass directly to a biorefinery, the desired system should aim to transform raw biomass into high-density, stable, commodity feedstocks at or close to the site of production. Biomass preprocessing at local preprocessing depots could become the link between biomass producers and refiners. Such depots would provide flexibility for local communities to produce feedstocks customized for biochemical, thermochemical, and combustion conversion facilities. But in addition, he said, preprocessing depots would also enable the production of renewable products, such as livestock feeds and soil amendments, that would increase the economic return on such facilities. Stokes described an ongoing effort at the Idaho National Laboratory to develop a highly instrumented, portable, modular process demonstration unit designed to represent one replicable depot that would address scale-up issues and produce quantities of densified materials meeting specific formulations.
In a uniform commodity feedstock vision, preprocessing depots would serve biomass production operations within a 5- to 20-mile radius. The uniform feedstock would then be transported by interstate trucks, short-line railroads, and internal waterways to shipping terminals similar to centralized grain elevators and then on to biorefineries as needed.
In closing, Stokes said that the physical and compositional characteristics of the feedstock determine conversion process and process efficiency and costs. One of the goals of research is to increase the value of the biomass feedstock, which would increase costs on the front end, but reduce costs further at the conversion end. Another goal going forward should be to increase biomass accessibility, he said. The nation has sufficient biomass resources, but its distribution does not match that of industry today. Finally, conservation and operational practices affect not only costs but intangible benefits for society as a whole. In summary, the United States has the land, the will, and by bringing our sciences together, we can provide the way to use biomass for feedstocks and commodities in our biorefineries.
Paul Bryan asked Stokes to list a few low-hanging fruits in terms of biomass supply. In response, he listed forestry residues and crop residues. Since these are already produced, the development of economical collection and preprocessing systems could produce results in the short term.
Emily Carter, from Princeton University, asked about the potential importance of algae and oil crops. Stokes replied that there was not enough information to include those in the Billion-Ton report, but that they do have real potential as energy and chemical feedstocks. He noted that some studies are including those sources. In response to a comment from Rich Green, of DOE, about the feasibility of boosting yields of biomass crops, Stokes noted that the Billion-Ton report places great faith in research, and particularly genomics, to boost crop yields.
Brian Duff, from DOE, began his presentation with a review of why biomass and biofuels are so important. He said that while he would focus his remarks on biofuels, he considers biofuels to be a representative subclass of chemical products that should be made from biomass. He also noted that it is important to consider what he characterized as the awe-inspiring scale of today’s global petrochemical industry when thinking about where the biomass conversion field is today. He added, though, that today is a very exciting time for this nascent endeavor given the convergence of the chemical sciences, synthetic biology, biotechnology, and environmental biotechnology.
Energy, said Duff, is a global challenge involving issues of security, the environment, and the economy, and clean energy offers potential solutions for each of these. Clean energy can translate into energy self-reliance and developing a stable, diverse energy supply that does not depend on importing oil from countries that can be antagonistic toward the United States. Developing locally produced clean, renewable energy could also reduce the amount that our military now spends to protect our access to imported oil. In terms of the environment, clean energy means clean air, mitigating climate change, and reducing greenhouse emissions.
Clean energy can also translate into jobs, rural economic development, and rebuilding a manufacturing base, as well as maintaining our innovation edge and reducing our dependence on a resource whose price fluctuations have a significant impact on the economy. DOE estimates that each biorefinery would produce 50-75 new direct jobs and an additional 3,000 indirect jobs supporting the biorefinery and its employees. A local source of clean energy would also have a major impact on the nation’s balance of trade, potentially eliminating the flow of $300 billion a year in economic value out of the country that could instead go to biomass producers and processers here in the United States (Figure 2-5). Developing a sustainable local source of biofuels will contribute greatly to maintaining the nation’s economic prosperity and quality life, said Duff.
He noted that the Department of Defense and the airline industry are, at least in part, driving the demand to develop biofuels. The airline industry, for example, will have to meet European sustainability and biofuels requirements. Other considerations, he said, are that liquid fuels are a premium product application unmatched in terms of energy density
FIGURE 2-5 The value of biofuels. The cost difference between importing crude oil and biomass.
SOURCE: EIA Annual Energy Review (Duff presentation).
and convenience. In the near term, biofuels are the only alternative that fits the U.S. lifestyle. In addition, given that biomass is not unlimited, the “best use” of biomass dictates that it be used in the highest value product applications. And while converting the nation’s auto and truck fleet to electricity sounds like a laudable goal, Duff added, that does not solve the greenhouse gas emissions as long as powerplants produce electricity using coal and natural gas. Liquid fuels from biomass, he stated, are really the only option in the near term.
The Potential of Biomass for Fuels, Chemicals, and Power
Biomass, said Duff, has the potential to dramatically reduce dependence on foreign oil for fuels and chemicals. It can also promote the use of a diverse, domestic and sustainable energy resource and establish a domestic bioeconomy, as well as reduce carbon emissions from energy production and consumption. He estimated that a national system of biorefineries would consist of 300 to 500 plants, creating jobs in rural economies that cannot be outsourced. Developing a biomass-based fuel economy would reduce carbon emissions and mitigate the direct and indirect costs of oil imports, with positive impacts on the balance of trade and demands on our military. It would also support and potentially expand U.S. leadership and innovation in chemical engineering and chemistry.
In creating a biorefinery infrastructure, pace will be as important as direction, Duff explained. It is not possible to replace a multi-trillion-dollar petroleum-based infrastructure with a biomass-based infrastructure overnight. The supply of biomass needed to support that infrastructure will not be available immediately either. It will be necessary to balance the pace of the transition with the cost of the resulting disruptions. Economics, he said, must be the driving force behind this transition. However, the economics of oil presents a real problem given that there are many non-monetized costs that do not appear in the price of oil. Biofuels, for example, have to meet a greenhouse gas emissions reduction requirement to meet the requirements of the Renewable Fuel Standard (RFS2) that oil does not. As Duff put it, biofuels have to perform all of the miracles of sustainability and still be priced lower than oil. That is a conundrum that challenges the biofuels community. He also noted that even under the provisions of RFS2, biofuels will only replace less than a quarter of the U.S. demand for liquid fuels.
According to DOE estimates, said Duff, the use of agricultural, forest, and urban waste streams, combined with energy crops and algae, could replace about 50 percent of imported crude oil. What is needed to meet this target, he explained, are flexible platforms that can process current and future products, and a portfolio approach that can be optimized across multiple feedstocks and regions. In thinking about such platforms, Duff’s program at DOE considers fermentable sugars, syngas, and biological oils from pyrolysis, oil seeds, and algae. These would be used to produce ethanol, renewable hydrocarbon fuels that match our current infrastructure’s needs, and home heating oil.
As far as greenhouse gas emissions are concerned, the transportation sector’s contribution is dwarfed by the power sector. Of the 985 gigawatts (GW) of electrical power generated in the United States, biomass—primarily waste and
wood—accounts for about 13 GW, or 1.3 percent of the total. Even if all of the 1 billion tons of biomass were diverted to energy production, it would account for only 47 GW, or 4.7 percent of demand. However, that same 1 billion tons of biomass would generate about 65 billion gallons of gasoline, which would meet about 30 percent of U.S. demand. The best use of biomass, said Duff, is for fuels and chemicals, and that includes diesel and jet fuel and a variety of specialty chemicals that also come out of every barrel of oil. Duff pointed out that although 70.6 percent of a barrel of oil is converted into fuels worth $385 billion annually, the 3.4 percent that is converted into petrochemicals is worth some $375 billion annually (Figure 2-6). Tapping into the enormous value of petrochemicals and specialty chemicals is a place where chemistry can play a huge role in realizing value from biomass conversion, particularly since these are high value added products that would use very little of the available biomass.
Biomass Supply and Value Chain
At DOE, the biomass program’s strategic focus is on achieving sustainability across the supply chain. This includes producing feedstocks in a way that preserves nutrients and maximizes carbon cycling, as well as minimizing the impact on land and resource use. In the conversion phase, the emphasis is on minimizing water consumption and air pollution while maximizing efficiency by integrating technology from feedstock to product. In the distribution step, the goal is to reduce the carbon footprint of new facilities and to use the co-products in order to maximize return and minimize risk associated with relying on a single product, such as ethanol. And finally, there has to be a product that is in demand. Each of these components will need to be integrated, for as Duff said, no one is going to grow a crop if there is no plant to take it to, and no one is going to finance a new plant if there is no crop or market for its product.
FIGURE 2-6 Value in a barrel of crude oil.
SOURCE: DOE (Image taken from Duff presentation).
From a value perspective, existing waste streams, both agricultural and municipal, have potential because they avoid impacts on food, feed, and land, nutrient, and water use. Duff said that new oilseed crops, algae, and fast-growing grasses and trees are also likely to fit into the value chain needed to make competitively priced biofuels. The challenge, as Stokes noted earlier, is in integrating all of these different sources of biomass into a consistent feedstock. He noted that research is under way on a real-time near-infrared monitoring system that would provide a compositional analysis of each truckload of biomass coming into a preprocessing depot. He also commented that biomass resources have low energy density, high water content, are perishable, and above all, have a high oxygen content compared to petroleum.
Before leaving this subject, Duff commented on the goal of $60 per dry ton of biomass. Today, companies in the United States are building pellet mills to ship biomass pellets to Europe that sell at a price of $120 per ton. In this case, European countries have decided to reduce dependency on Russia and Ukraine for natural gas and power and they are willing to pay a premium price to achieve that goal. He said the only way to get to $60 or lower per dry ton is by developing processing technologies that increase bulk density and improve harvesting efficiency. Another possibility is to realize the potential of algal production of biomass and feedstocks as part of an integrated biorefinery.
There are two basic options for converting biomass to product—biochemical and thermochemical. Duff explained that there are two classic thermochemical options, gasification and pyrolysis, each of which produces different intermediates. Gasification involves rapid heating and partial oxidation to produce syngas, which is largely carbon monoxide and hydrogen (see Figure 2-7). This process operates at very high temperature and also produces unconverted tars that must undergo reforming. Contaminants in syngas output must be removed to avoid deactivating or destroying the efficiency of downstream catalytic process operations. While gasification works well with petroleum and natural gas, the sulfur, nitrogen, phosphorous, potassium, and mineral content of biomass complicates matters. Also, the high oxygen content of biomass results in the production of significant quantities of carbon dioxide, which reduces carbon efficiency. Research by chemists and chemical engineers is needed to develop new catalysts that resist contamination and have improved selectivity. The advantage of syngas is that it creates a blank slate of single carbon atoms that can be used to build many possible molecules, including gasoline, diesel, and jet fuel, and a variety of value-added building blocks such as methanol, ethylene, and naphtha. Syngas, said Duff, has the potential to replace the entire barrel of oil except perhaps for asphalt.
In pyrolysis, lower temperatures are used to break down biomass into smaller molecules such as oxygenated aromatics, ketones, organic acids, and other oxygenates, as well as light hydrocarbon gases (see Figure 2-8). In addition to the lower energy input to achieve biomass deconstruction, pyrolysis has a high theoretical yield for liquid products. With upgrading, the pyrolysis products can be fed directly into existing petrochemical refineries.
The classic biochemical conversion route involves pretreating biomass with either enzymes or acid to release sugars that are then fermented. Another biochemical route uses anaerobic digestion to produce methane, though several new technologies short-circuit this process prior to full degradation to methane in order to produce carboxylic acids that can then be converted into diesel and jet fuel. Duff believes there is a great deal of potential for other products to come
FIGURE 2-7 Thermochemical conversion of biomass via gasification.
SOURCE: DOE (Image taken from Duff presentation).
FIGURE 2-8 Thermochemical conversion of biomass via pyrolysis and drop-in points that could use today’s petrochemical infrastructure.
SOURCE: Image taken from Duff presentation.
out of this type of process development. In addition, there is a new process called electrofuels that is attempting to capitalize on geoautotrophs and other bacteria that create energy by metabolizing minerals or even electricity and use that energy to produce fuel molecules. DOE is investing heavily in research aimed at developing the electrofuels process to synthesize fuel. There are also hybrid systems under development, such as one that merges syngas production via gasification with bacterial fermentation to produce fuel and another that takes the sugars produced from biomass degradation and uses chemical catalysts to convert them into fuel.
The last pathway that DOE is investigating uses algal oil as an intermediate that is then upgraded to make fuel (see Figure 2-9). Again, substantial research and development is needed for the use of algal oil at a commercial scale. One of the most significant challenges algal oil faces is its heavy use of water.
Duff concluded his talk by noting that the list of building blocks, secondary chemicals, intermediates, and end products that can be made from biomass feedstocks is virtually limitless, just as it is with petroleum. One issue that needs to be solved is the high oxygen content of biomass; aviation fuels, diesel, and gasoline all have low oxygen requirements. Again, this a place where chemists can contribute greatly by developing catalysts to deoxygenate biomass intermediates.
Tom Richard, of Pennsylvania State University, asked why so much effort is being put into the production of sugars from biomass when organic acids may have more uses as chemical feedstocks. Duff agreed with that assessment and noted that work on oilseeds and algae are more heavily focused on organic acid production. He added that it would be a good idea to look at the conversion of lignocellulose into organic acids rather than sugars.
From the perspective of greenhouse gas mitigation, commented David Stern of ExxonMobil, the best use of biomass would be to burn it and make electricity and he wondered why DOE was not looking at the power option for biomass. Duff agreed with that assessment but noted that converting a billion pounds of biomass into electricity would be miniscule compared to reducing greenhouse gas output by the power generating industry. He added that sustainability is about more than greenhouse gas emissions; in his mind, quality of life is an important consideration. Stern agreed with that remark and added that he felt that the real value of biomass conversion lies in rural development and job creation as part of the bigger picture of sustainability. Paul Bryan also voiced support for looking at sustainability through this larger lens.
FIGURE 2-9 The intermediate produced by the algal pathway is algal oil.
SOURCE: Image taken from Duff presentation.
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