The third session of the workshop examined the potential impacts of unconventional hydrocarbon production on aquatic and terrestrial ecosystems, air quality, and climate. Four plenary talks were followed by working group discussions, which focused on potential impacts, methods for reducing these impacts, and priorities for future research, as summarized below.
Potential Impacts of Unconventional Hydrocarbon Production on Stream Biota: Current and Needed Research
Kelly Maloney, U.S. Geological Survey
Maloney noted that little data have been collected on the direct effects of hydrocarbon production on stream biota, and so inferences have to be drawn from research on other types of disturbances to landscape conditions, such as agriculture, urbanization, and road construction. Stream communities—including primary producers (e.g., algae, plants), benthic microinvertebrates (e.g., insects, crayfish), fish, amphibians and reptiles, and birds and mammals—are sensitive to these disturbances and have been studied for decades to assess stream health.
Stream ecosystems may be affected by unconventional hydrocarbon production, particularly site preparation, which disturbs the land surface, and the use, treatment, and disposal of water. Recent research has highlighted three key potential issues for stream biota: habitat fragmentation, stream flow alteration, and degradation of water quality. Habitat fragmentation arises from the installation of roads and pipelines, which bisect landscapes, and from the loss of land through development of well sites. The Nature Conservancy (Johnson, 2010) estimated that the production infrastructure (roads, pipelines, well pads, impoundments) disturbs about 9 acres per well pad. Habitat fragmentation affects species in several ways. Smaller patches of habitat have lower diversity, and when patches of habitat become isolated from one another, it becomes more difficult for species to
interact. The net effect is lower recolonization, reduced population sizes, and genetic bottlenecks. A fragmented habitat also has more edges, which benefits some species and harms others.
Water used in the hydrocarbon production process is often taken from streams and rivers, reducing or altering stream flows in ways that may adversely affect stream biota. For example, withdrawals that reduce pools below a threshold size at key times (e.g., spawning, incubation) can result in habitat loss. Temporary dams constructed to impound water (cofferdams) can change the stream conditions from lotic (flowing water) to lentic (still water), altering the habitat. Withdrawals of water that expose substrate can desiccate taxa that cannot move and also isolate pools, potentially stranding species and raising water temperatures above levels tolerated by some species. In a worst-case scenario, water withdrawals could alter the natural flow regime (quantity, timing, and variability of stream flow) on which stream organisms depend, negatively affecting instream biota.
Stream water quality may be degraded by contamination from spills and by sedimentation. Of particular concern are contaminants that increase stream salinity or decrease pH, which control the distribution of species in aquatic habitats, and heavy metals, which may accumulate in tissues, affecting physiology, growth, behavior, and reproduction. Research documenting sediment runoff from well pads shows a positive correlation between well density and stream turbidity. Sedimentation in streams can result in a loss of habitat or a loss of sensitive species. The extra sediment carried by streams may bury primary producers such as algae or scrape them off rocks, or it may fill interstitial habitats favored by benthic microinvertebrates or overwhelm the ability of these organisms to filter feed or breathe. Impacts to fish include reduced foraging efficiency, loss of pool and spawning habitat, and increased mortality of eggs laid in interstitial areas as a result of oxygen deprivation or sediment burial. Sediment also coats egg masses of amphibians and reptiles and may lead to a loss of sensitive species.
A few programs are beginning to be developed to restore habitats affected by the energy industry. For example, Wildlife Incentives for Nongame and Game Species (WINGS) is an effort by local government agencies, land trusts, and energy companies to create or enhance wildlife habitats along natural gas pipeline and electricity corridors.1
Maloney concluded with some topics for discussion, including the extent to which the wealth of data from activities such as agriculture and construction can be used to guide management and research on unconventional hydrocarbon production. Other issues include the availability of indicator species or biomarkers to detect habitat disturbance, the effects of habitat fragmentation and invasive species on stream ecosystems, and the efficacy of industry best management practices.
Questions. A workshop participant noted that short-term impacts can be measured (e.g., number of fish killed from a chemical spill). How can long-term impacts be measured? Maloney said that events such as a spill can be hard to detect because they move through the system quickly. Real-time monitors that collect data routinely are needed to detect a stress or mortality event. Monitoring and research are also needed to assess longer-term impacts, such as those caused by sedimentation. Sediment can be held in reservoirs for decades, and so the impacts may lag the activity that produced erosion and runoff.
The same participant observed that research, monitoring, and impact analysis cost money. Work on acute events is difficult to do without timely access to funds, and funding for water monitoring is declining. Some participants added that funding for stream flow measurements has been declining since about 1980. Moreover, proposals that include monitoring are not well reviewed by peers or by National Science Foundation program managers. Other participants thought that government and academic researchers are always going to be behind the curve because of the difficulty of raising funding, the time it takes to analyze results, and the dynamic nature of the industry.
Several participants suggested ways to stretch funding or partner with industry. Maloney thought that more use could be made of existing data sets, such as those collected by state agencies. Other participants suggested university or government collaborations with industry to obtain industry funding, data, or insights. Sustained collaboration could generate the knowledge and data sets needed to answer key questions and monitor environmental impacts.
Assessing and Minimizing Ecological Impacts of Shale Development
Michael Powelson, The Nature Conservancy
Powelson discussed the potential environmental footprint of unconventional hydrocarbon development. The Nature Conservancy develops ecological scenarios using information on reserves and current trends in energy development to create models of future development patterns. Ecological data on intact habitats, species distribution, migration patterns, and climate resilience are then integrated into the models to project potential long-term ecological impacts. Powelson showed several example projections. Under a medium-development scenario (10,000 new well pads by 2030, about 60 percent in forested areas), most of the intact forest blocks in central Pennsylvania would be eliminated or fragmented by 2030 (Figure 4.1). This is important because intact forest blocks are the critical resource that maintains biodiversity. A high level of development (15,000 new well pads by 2030) would affect more than half of the habitat occupied by brook trout and by black-throated blue warblers, two potentially endangered species.
Powelson emphasized that certain habitats, species, and ecosystems provide crucial ecological value to larger systems and landscapes. Development in these areas could reduce the viability and resilience of the entire ecosystem or landscape. He thought that avoiding development may be the
FIGURE 4.1 Projected forest fragmentation in 2030, assuming 10,000 new well pads with an average of 6 wells per pad. SOURCE: The Nature Conservancy.
most effective way to minimize ecological impacts. When avoidance is not feasible, steps can be taken to minimize impacts (e.g., by collocating roads and pipelines) or to offset impacts (e.g., by restoring affected areas). Both strategies would be facilitated by landscape-level planning, which examines cumulative effects across a broad geographical region and conservation priorities, as well as investigation and monitoring of ecological impacts.
Questions. A workshop participant said that many environmental advocacy groups are trying to articulate best management practices for industry, but ongoing technological developments cause these best practices to constantly evolve. What is the current landscape of best management practices, and are industry players sharing their most recent developments? Powelson agreed that there are many sets of best management practices, including some developed in partnership with industry (e.g., practices for minimizing methane emissions and impacts on water quality developed for the Marcellus Shale by the Environmental Defense Fund, Shell, Chevron, and QET). Most of the industry is trying hard to minimize the environmental footprint; the problem is that there are some bad actors.
Assessing Emissions of Hydrocarbons from Rural and Natural Gas Drilling Impacted Areas in Pennsylvania
Jose Fuentes, Pennsylvania State University
Fuentes noted that hydrocarbons enter the atmosphere from several sources, including active and abandoned wells, storage tanks, and pipelines. The heavy machinery and vehicles used in the gas production process also release compounds into the air. These hydrocarbons remain in the atmosphere only in trace amounts, but they react with constituents such as hydroxyl radicals and thus can influence the oxidation capacity of the atmosphere. The reaction products of these gases are precursors to pollutants such as carbon monoxide and ozone. They also condense readily in the atmosphere and form aerosols, which affect cloud formation and regional climate. Finally, elevated concentrations of hydrocarbon species such as benzene, toluene, ethylbenzene, and xylene (BTEX) can adversely affect human health.
Fuentes’s research team has been taking air samples across Pennsylvania to determine whether activities associated with natural gas production have a measurable impact on regional levels of hydrocarbons in the atmosphere. Samples were taken from rural areas to establish a baseline, from state parks to examine diurnal variability in biogenic hydrocarbons (i.e., those produced by trees in the daytime), and from areas near different types of gas production activities (drilling, flaring, operating for different periods). The results show that BTEX levels are very low in mostly forested areas. In areas with a high density of wells, the atmosphere contains more anthropogenically emitted hydrocarbons and fewer biogenic hydrocarbons.
Approximately 120 chemical species of hydrocarbons were found in the Pennsylvania air samples. For the most common of these species, the alkenes, concentrations were similar in all settings: native, forested, agricultural, gas well-impacted, and urban. BTEX was higher in urban settings than other settings, likely because cities have many sources of toluene, benzene, and xylene. Finally, isoprene and other gases that come from forests are among the hydrocarbon species with the greatest potential to affect the chemistry of the atmosphere through reactions with hydroxyl radicals.
Fuentes also showed some preliminary results from air samples taken at a farm. Passing vehicles create spikes in nitrogen oxides, which affect ozone formation and air quality. Steps that could be taken to understand the interaction between nitrogen oxides and hydrocarbons in the Appalachian region include establishing an air sampling network to identify species and sources of
hydrocarbons and developing numerical models to calculate emissions. A baseline of observations would also help industry determine when and where leaks of methane occur.
Questions. A participant asked how to reconcile top-down and bottom-up measurements when designing a monitoring network. Fuentes said that both approaches are necessary. For reactive gases, monitoring stations must be close to the wells because some of those gases are short-lived. For long-lived gases such as methane, inferential (top-down) methods can be used to calculate the source or the strength of the leaks.
Climate Impacts of Shale Gas
Paulina Jaramillo, Carnegie Mellon University
Jaramillo discussed the climate impacts of unconventional shale gas production from a life-cycle perspective, which tallies impacts from preproduction (well-pad preparation, well drilling, hydraulic fracturing, well completion), production, processing, transmission and distribution, and combustion of the shale gas. Sources of emissions include fuel use, flaring and venting, methane leaks throughout the system, water consumption, pad construction, vegetation clearing, and the production of drilling mud and additives. Studies (e.g., Jiang et al., 2001) show that combustion is the dominant source of emissions over the life cycle of shale gas. The main sources of emissions from preproduction through distribution depend on the production rate and lifetime of the well. For a well that produces 3 million cubic feet of gas per day for 25 years, emissions are dominated by the production stage. For a well that produces only 0.3 million cubic feet of gas per day and lasts only 5 years, a significant fraction of emissions comes from the preproduction stage.
The data used to estimate emissions have a variety of uncertainties. The results of an uncertainty and variability analysis of life-cycle greenhouse gas emissions from natural gas are shown in the probability distribution in Figure 4.2. Superimposed on this distribution are life-cycle emissions estimates from other published studies (colored dots). Most of these estimates fall within the 90 percent confidence interval (62–72 g CO2e/MJ) of the probability distribution, although one (Howarth et al., 2011) is significantly higher, in part because the analysis assumed a higher loss of natural gas throughout the life cycle of the system.
The effect of natural gas on climate depends not only on how much methane and carbondioxide is going into the atmosphere (discussed above), but also on how the gas is used (e.g., electricity generation, industrial and home heating, transportation). Gas use has many elements. Emissions associated with electricity generation, for example, depend on the relative efficiencies of natural gas and coal power plants, how power plants are scheduled to produce energy (which depends on the marginal cost of production, technological constraints, and the need to instantly match supply and demand), plans to retire coal plants, and how renewable energy sources, which produce variable and intermittent energy, are integrated into the power system. Emissions from electricity generation can be reduced by replacing coal with natural gas because emissions from natural gas are lower than those for coal, and new natural gas power plants are significantly more efficient than coal plants. However, the reductions depend partly on the price of natural gas. A recent study (Venkatesh et al., 2012) found that the maximum reduction in emissions from the power system is about 15 percent when the life cycle of the fuels is considered, and much less if the price of natural gas rises above $3.5 per million BTUs (British thermal units).
These factors add considerable complexity to the analysis of climate impacts from natural gas. Climate impacts are generally assessed using climate models, but complexities in emission sources and energy uses are only beginning to be incorporated in models. For example, a recent study (Wigley, 2011) used a simplified climate model to examine how replacing coal with natural gas at
FIGURE 4.2 Probability distribution (histogram) representing the uncertainty and variability in greenhouse gas emissions from activities in the life cycle of domestic natural gas. SOURCE: Adapted with permission from Venkatesh et al. (2011b). Copyright 2011 American Chemical Society. Superimposed are estimates from studies of life-cycle emissions from unconventional and conventional hydrocarbon production (blue and green dots, respectively). SOURCE: Paulina Jaramillo, Carnegie Mellon University.
a rate of 1.25 percent per year would affect temperature, assuming that a percentage of methane leaks into the atmosphere. The study found that the switch to natural gas would produce short-term (decades) warming because methane leakage warms the atmosphere and aerosols produced by coal combustion cool the atmosphere.
Jaramillo concluded that the life-cycle greenhouse gas emissions from shale gas can be higher than those from conventional gas. However, she noted the need for additional impact assessments and climate modeling to assess the impact of shale gas on climate and for displacement analysis to assess the effect of changing fuel sources on climate. She also thought that a proper regulatory framework is needed to manage all environmental impacts.
Questions. A workshop participant noted that the maximum leakage rate (7.7 percent)2 estimated in a National Oceanic and Atmospheric Administration study (Pétron et al., 2012) is controversial. In an analysis of the work, Levi (2012) estimated that leakage rates are closer to 1 to 2 percent. Greg Frost, a coauthor of the Pétron et al. (2012) article, said that the Levi (2012) paper correctly pointed out the unreliability of inventory information used to interpret the atmospheric measurements in terms of emissions. However, alternative methods produce the same results: a leakage
2 Pétron et al. (2012) report natural gas losses ranging from 2.3 to 7.7 percent, with an expected value of 4.4 percent.
rate of about 4 percent in the Denver-Julesburg Fossil Fuel Basin in Colorado and about 9 percent in Utah. Jaramillo added that published studies suggest an overall leakage rate of about 3 percent, although rates may be higher in particular fields.
Another participant commented that two ExxonMobil researchers recently evaluated life-cycle emissions using data from Marcellus well sites, compressor stations, and other measurements (see Laurenzi and Jersey, 2013).
Each working group was asked to consider the following themes:
• Potential effects on landscapes, including soil and living organisms, and other environmental systems—Connections between hydraulic fracturing and other production technologies and processes on environmental systems, including scientific data and methods in assessing impacts;
• Technical and engineering processes—Methods for limiting and mitigating the impacts of developing and producing hydrocarbons from unconventional resources on landscapes, ecosystems, and climate; and
• Research priorities—Scientific and engineering research needed to narrow or characterize uncertainties.
A wide range of issues related to these themes were raised by the working groups. Issues that were raised by multiple working groups or that were raised for the first time in the workshop are summarized below. The complete working group reports appear in Appendix D.
Research Priorities and Issues
Working groups identified a wide range of environmental issues for further study. These included understanding impacts at different temporal and spatial scales, from individual species (thresholds and tipping points) to landscapes (erosion and sedimentation, spills, topographic alteration, road use, and habitat disruption) to the atmosphere (toxins and particulate matter) and climate (greenhouse gas emissions over the life cycle of the well). Some of the working groups discussed the need to compare or untangle the environmental impacts from legacy conventional wells and modern shale gas wells.
The long timescales required to study the environmental impacts of shale gas development pose problems for research (e.g., difficulties of obtaining funding for monitoring). Some working groups thought that industry might be willing to provide long-term funding for applied research and the development of low-cost monitoring networks and large data management systems. However, industry practices change much faster than research results are generated, so it is a challenge to keep research studies and partnerships relevant to industry.
Baseline and monitoring data were key issues of the working groups. Several working groups stressed the need for standardized data collection and sampling methods. Careful thought about the problem could help target data collection to the right parameters, areas, and timescales. Some working groups suggested involving citizens, extension services, or county conservation agents in data collection or monitoring. For example, the development of sensors that are inexpensive and easy to operate, such as those on weather stations operated by volunteers,3 could significantly
expand data collection. Better access to government and industry data would also increase the pool of data available for research.
Public Perception and Education
Some of the working groups noted that citizens make decisions and take positions on shale gas production based on potential impacts to people (e.g., increased traffic, light, noise, and odors from generators and compression stations) or to ecosystems (e.g., habitat fragmentation or loss). Consequently, it is important that scientists communicate clearly what is known about sociological and ecological impacts. Extension services may also be able to play a role in public communication and education.
One working group pointed out that research alone is unlikely to change public perceptions. Good management could reduce the sociological impacts of light, noise, and traffic and also improve public perceptions. Proceeding conservatively with development until potentially large ecological impacts are better understood may also be a useful strategy. Some individuals said that the industry already takes ecological impacts into consideration when planning development.
Technical and Engineering Issues
The working groups identified a number of technical and engineering issues that need further attention, including placing wells, pipelines, and facilities in locations that minimize environmental impacts while optimizing hydrocarbon production; and developing techniques and strategies to reduce the effect of noise and light pollution on ecosystems and communities. Although one working group agreed that measures to reduce fugitive emissions are needed, it disagreed on where mitigation efforts should be focused (e.g., leaky pipes in cities may have higher fugitive emissions than shale gas production). One working group noted the importance of a responsible operation philosophy and best management practices.