Emily Grubert

Can switching fuels save water? A life cycle quantification of freshwater consumption for Texas coal-and natural gas-fired electricity

Thermal electricity generation is a major consumer of freshwater for cooling, fuel extraction and air emissions controls, but the life cycle water impacts of different fossil fuel cycles are not well understood. Much of the existing literature relies on decades-old estimates for water intensity, particularly regarding water consumed for fuel extraction. This work uses contemporary data from specific resource basins and power plants in Texas to evaluate water intensity at three major stages of coal and natural gas fuel cycles: fuel extraction, power plant cooling and power plant emissions controls. In particular, the water intensity of fuel extraction is quantified for Texas lignite, conventional natural gas and 11 unconventional natural gas basins in Texas, including major second-order impacts associated with multi-stage hydraulic fracturing. Despite the rise of this water-intensive natural gas extraction method, natural gas extraction appears to consume less freshwater than coal per unit of energy extracted in Texas because of the high water intensity of Texas lignite extraction. This work uses new resource basin and power plant level water intensity data to estimate the potential effects of coal to natural gas fuel switching in Texas’ power sector, a shift under consideration due to potential environmental benefits and very low natural gas prices. Replacing Texas’ coal-fired power plants with natural gas combined cycle plants (NGCCs) would reduce annual freshwater consumption in the state by an estimated 53 billion gallons per year, or 60% of Texas coal power’s water footprint, largely due to the higher efficiency of NGCCs.

Rigor in social life cycle assessment: improving the scientific grounding of SLCA

PurposeSocial life cycle assessment (SLCA) is developing rapidly and represents a valuable complement to other life cycle methods. As methodological development continues, a growing number of case studies have noted the need for more scientific rigor in areas like data collection, allocation methods, and incorporation of values and cultural context. This work aims to identify opportunities, especially in the social sciences, to improve rigor in SLCA.MethodsA review of existing literature and tools is based on both hand coding of the SLCA literature as represented in Web of Science’s “All Collections” database and on computer-aided review of the SLCA and other related literatures (including social impact assessment (SIA), life cycle sustainability assessment (LCSA), and corporate social responsibility (CSR)) using a text mining technique known as topic modeling. Rapid diagnosing of potentially valuable contributions from literatures outside of SLCA through computer-aided review led to more detailed, manual investigation of those literatures for further insight.Results and discussionData collection can benefit from increased standardization and integration with social science methods, especially frameworks for surveys and interviews. Sharing examples of questionnaires and ethics committee protocols will likely improve SLCA’s accessibility. SIA and CSR also represent empirical data sources for SLCA. Impact allocation techniques can benefit from reintegration with those in ELCA, in particular by allocating (when necessary) at facility—rather than product—level. The focus on values and subjectivity in SLCA is valuable not only for SLCA but also for other methods, most notably ELCA. Further grounding in social science is likely to improve rigor in SLCA.ConclusionsSLCA is increasingly robust and contributing to interdisciplinary discussions of how best to consider social impacts. This work makes three major recommendations for continued growth: first, that SLCA standardize human subject research used for data gathering; second, that SLCA adopt allocation techniques from ELCA; and third, that SLCA continue to draw on social science and other literatures to rigorously include value systems.

Energy for water and water for energy on Maui Island, Hawaii

Energy and water systems are interconnected. This work first characterizes 2010 primary energy demand for direct water services and local freshwater demand for energy on Maui Island, Hawaii, then investigates scenarios for future changes in these demands. The goal of this manuscript is to dissect the relationship and trends of energy–water connections to inform policymaking decisions related to water and energy planning. Analysis proceeds by inventorying water and energy flows and adjusting to a 2010 base year, then applying intensity factors for energy or water used at a given stage for a given sector to determine absolute energy and water demands for the isolated system of Maui Island. These bottom-up, intensity-based values are validated against published data where available. Maui consumes about 0.05% of its freshwater for energy (versus >6% for the US on average) and about 32% of its electricity (19% of its on-island primary energy) for direct water services (versus 8% of primary energy for the US on average). These values could change with policy choices like increased instream flows, higher wastewater treatment standards, electricity fuel mix changes, desalination, or increased biofuels production. This letter contributes a granular assessment of both energy for water and water for energy in a single isolated system, highlighting opportunities to address energy–water interdependencies in a context that could be relevant in other communities facing similar choices.

Implicit prioritization in life cycle assessment: text mining and detecting metapatterns in the literature

PurposeLife cycle assessment aims to evaluate multiple kinds of environmental impact associated with a product or process across its life cycle. Objective evaluation is a common goal, though the community recognizes that implicit valuations of diverse impacts resulting from analytical choices and choice of subject matter are present. This research evaluates whether these implicit valuations lead to detectable priority shifts in the published English language academic LCA literature over time.MethodsA near-comprehensive investigation of the LCA literature is undertaken by applying a text mining technique known as topic modeling to over 8200 environment-related LCA journal article titles and abstracts published between 1995 and 2014.Results and discussionTopic modeling using MALLET software and manual validation shows that over time, the LCA literature reflects a dramatic proportional increase in attention to climate change and a corresponding decline in attention to human and ecosystem health impacts, accentuated by rapid growth of the LCA literature. This result indicates an implicit prioritization of climate over other impact categories, a field-scale trend that appears to originate mostly in the broader environmental community rather than the LCA methodological community. Reasons for proportionally increasing publication of climate-related LCA might include the relative robustness of greenhouse gas emissions as an environmental impact indicator, a correlation with funding priorities, researcher interest in supporting active policy debates, or a revealed priority on climate versus other environmental impacts in the scholarly community.ConclusionsAs LCA becomes more widespread, recognizing and addressing the fact that analyses are not objective becomes correspondingly more important. Given the emergence of implicit prioritizations in the LCA literature, such as the impact prioritization of climate identified here with the use of computational tools, this work recommends the development and use of techniques that make impact prioritization explicit and enable consistent analysis of result sensitivity to value judgments. Explicit prioritization can improve transparency while enabling more systematic investigation of the effects of value choices on how LCA results are used.

Response to "Discourse over a contested technology on Twitter: A case study of hydraulic fracturing"-Word choice as political speech.

Hopke and Simis (Public Understanding of Science, online 4 October 2015) find that #fracking, the most popular of five shale-related hashtags analyzed from a 2013 period, is associated with pro-shale attitudes only 13% of the time and note that the dominant voice of the activist community, coupled with a lack of engagement from industry, is unexpected. This comment offers additional perspective on the sentiment- and actor-skewed result by noting that the term “fracking” is highly political, specifically because the spelling “frack” versus “frac” is associated with activism. Furthermore, in public speech, the industry tends to deemphasize the hydraulic fracturing process in favor of the product, consistent with the findings that #natgas is a relatively pro-industry hashtag.

The Need for a Preference-Based Multicriteria Prioritization Framework in Life Cycle Sustainability Assessment

Life cycle thinking is a valuable tool for integrated assessment of the environmental, social, and economic outcomes of human activities. The combination of the three as life cycle sustainability assessment (LCSA) is a powerful decision support tool, but it also presents important design challenges. Among the most important challenges is how to include subjective information necessary for defining the major elements of a decision: prospects to decide among, uncertainty, risk attitudes, and preferences. Previous work on values in life cycle methods has addressed prospects, uncertainty, and risk attitudes. This article builds on that work by arguing that given LCSAs broad scope, explicit and standardized intercategory preferences are especially important for improving its value for decision makers. Practitioners should not be solely responsible for the value judgments necessary to integrate impact categories within and across environmental life cycle assessment (E†LCA), social LCA (S†LCA), and life cycle costing evaluations for LCSA. Neither should this task fall entirely to decision makers, particularly as life cycle–grounded decisions are highly sensitive to value frames. Individuals are unlikely to be able to meaningfully interpret, evaluate, and determine trade†offs without support. This article thus proposes that LCSA leverage its multiple paradigms to rigorously generate explicit, empirically grounded intercategory preference archetypes for use in evaluating decision robustness, much as cultural theory†based archetypes are currently used to test robustness to risk attitudes. Proof†of†concept data from the United States illustrate this approach, named WELFARES.

Water for Biomass-Based Energy on Maui, Hawaii

Biomass-based energy has characteristics that could help Maui Island meet multiple long-term goals, including decreasing reliance on oil for electricity and transportation fuels, increasing use of local resources that do not need to be shipped long distances, and diversifying the island economy beyond tourism by preserving agriculture. Biomass can be used for liquid fuel production and for electricity production. On Maui, sugarcane has been grown at plantation scale for over a century. Accordingly, sugarcane-derived ethanol and combustible sugarcane bagasse have long been of interest as energy sources for the island. State and county level focus on increasing renewable energy utilization on Maui have renewed study of potential crops and available land, with a special emphasis on sugarcane. However, there is some concern about the water requirements associated with biomass-based energy. A primary motivation for using local, renewable energy sources is that Maui is an island with limited resources, fresh water among them: thus, exploring ways to increase energy sustainability without compromising water availability is of interest to many. This work examines the water needs associated with growing sugarcane for ethanol and combustible biomass on Maui Island. Virtually all sugarcane on Maui is irrigated because soil and sunlight resources do not generally coincide with natural precipitation patterns. Growing sugarcane for energy represents a large water demand that is limiting under certain development scenarios on Maui, such as a scenario where environmental streamflows are highly prioritized. By comparing the irrigation demand of Maui’s currently grown sugarcane with published figures for ethanol yield from cane, this work finds that 700 to 1,500 gallons (gal) of irrigation water are needed per gallon of sugarcane-based ethanol (from fermentable sugars and fiber; 0.7 to 1.5 cubic meters, m3 , per liter, L). More water is needed for processing. However, combustible waste streams could provide additional energy return per unit of water. This paper discusses how water demand for sugarcane-based energy interacts with other island water demands, given that about 37,000 acres (150 km2 ) of sugarcane land are potentially available for bioenergy production. Though seawater cannot be successfully directly used for irrigation, sugarcane can tolerate some salinity and other contamination, so this paper also considers brackish water and treated wastewater — for which there is little other demand — as potential irrigation resources. Notably, the range of tolerable water quality expands significantly when sugarcane is not intended for human ingestion or when biomass yield, not sugar content, is targeted (as for cellulosic ethanol or combustible biomass production).Copyright

Water Use in the United States Energy System: A National Assessment and Unit Process Inventory of Water Consumption and Withdrawals

The United States (US) energy system is a large water user, but the nature of that use is poorly understood. To support resource comanagement and fill this noted gap in the literature, this work presents detailed estimates for US-based water consumption and withdrawals for the US energy system as of 2014, including both intensity values and the first known estimate of total water consumption and withdrawal by the US energy system. We address 126 unit processes, many of which are new additions to the literature, differentiated among 17 fuel cycles, five life cycle stages, three water source categories, and four levels of water quality. Overall coverage is about 99% of commercially traded US primary energy consumption with detailed energy flows by unit process. Energy-related water consumption, or water removed from its source and not directly returned, accounts for about 10% of both total and freshwater US water consumption. Major consumers include biofuels (via irrigation), oil (via deep well injection, usually of nonfreshwater), and hydropower (via evaporation and seepage). The US energy system also accounts for about 40% of both total and freshwater US water withdrawals, i.e., water removed from its source regardless of fate. About 70% of withdrawals are associated with the once-through cooling systems of approximately 300 steam cycle power plants that produce about 25% of US electricity.

Communication Science for Science Communication: Water Management for Oil and Natural Gas Extraction

AbstractWater management for oil and natural gas extraction in the United States has become a topic of public interest and concern. This societal relevance simultaneously heightens the need for rig...

Synthetic Flows for Engineered Systems with Nonstationary Parameters: Study of Maui’s Wailoa Ditch

AbstractWater flow through engineered channels is important for decision making given its close ties to availability for allocation. However, planners often rely on estimates for natural streamflow, then use stream-by-stream assumptions and aggregation to estimate allocatable flows rather than directly assessing flows through engineered channels. Further, synthetic flows based on historical records can be unreliable when parameter nonstationarity due to effects like climate change is likely. This case study of the Wailoa Ditch, a major engineered surface water supply system on Maui, Hawaii, uses a natural experiment based on Maui’s declining rainfall to demonstrate and validate that both problems can be addressed. For Wailoa, synthetic and actual flow characteristics differ by less than 5% when historical records are adjusted to reflect changing rainfall. Direct simulation of Wailoa’s flows reproduces modern conditions more accurately than stream-by-stream approximations. Precipitation-based scenario anal...