LOCATION: 2306
16:00 Syeda Mariya AbsarMaria Fernanda Campa and Adam Taylor

Life Cycle Water and Carbon Footprint of Barnett Shale Gas

ABSTRACT. Shale gas and oil production is on the rise in the United States. While the increase in shale gas production is reducing the overall greenhouse gas emissions of the United States, because it is replacing coal usage, shale gas production is a water and energy intensive process.

This study estimates the life cycle water consumption and wastewater generation, and the life cycle greenhouse gas emissions from the production of Barnett shale gas in Texas. This life cycle assessment is done for a shale gas well from its construction to the end of life. The data for the Barnett wells is collected from literature review and publicly available natural gas extraction inventories. Similar studies have been done for the Marcellus shale play but there is little information available for the Barnett shale play. This data will be used to create a life cycle inventory for shale gas production using SimaPro software. The life cycle direct water quality pollution impacts will be assessed using the Environmental Protection Agency’s tool for the reduction and assessment of chemicals and other environmental impacts (TRACI). The water consumption index will be calculated using the Water Footprint – Hoekstra et al 2012 water scarcity method. Global warming potential will also be quantified using the TRACI model.

Our results will be reported as GHG emissions in kgCO2eq/MWh and water consumption in gal/MWh. Based on the results and life cycle assessments, wastewater treatment costs and management options will be proposed. The results will also provide a thorough understanding of the water consumption and greenhouse gas emissions from shale gas production in the Barnett shale play. These outcomes will help to estimate the impacts of the rapid growth in shale production on water availability in Texas. In addition, our results will inform discussions on the contribution of shale gas to greenhouse gas emissions reductions in the US.

16:15 Aranya VenkateshRamkumar Karuppiah and Adam Usadi

Spatially- and temporally-explicit water stress indices for use in life cycle assessment

ABSTRACT. In the light of local water scarcity concerns in regions across the world, it is important to understand the dynamics of regional water supply and demand. Water stress indices (WSIs) have been developed as quantitative indicators of water scarcity in different areas – they are typically estimated as a function of the water use and availability in any region. Application of these indices helps us understand water supply and demand risks for multiple users, including those in the agricultural, industrial, residential and commercial sectors. Previous studies have developed methodologies to calculate WSIs that were used to estimate characterization factors (CFs), in order to quantify environmental impacts of freshwater consumption within a life cycle assessment (LCA) framework. In these studies, global WSIs were based on data from publicly available databases and have been reported as annual averages for multiple watersheds. The resolutions used in these literature studies typically do not effectively differentiate between seasonal and permanent water scarcity. A recent study1 improves upon the temporal and spatial resolution of the water scarcity calculations used to estimate WSIs, and offers a more robust framework for risk assessment, with a case study focused on the Mississippi river basin. A physical hydrological model, the Soil and Water Assessment Tool (SWAT), was used to simulate water supply in the Mississippi river basin with high spatial and temporal resolution. The basin was divided into about 450 sub-basins for which water availability was simulated and aggregated to monthly and annual timescales time-scales. Input data to SWAT included weather, land use and soil characteristics, all from publicly available global data sets. The hydrological model was calibrated against observed monthly river discharge within sub-basins, and compared against observed evapotranspiration, with improved results compared to global models. The calibrated results were used to estimate monthly- and annually-averaged WSIs for the sub-basins. The results from this study suggest that global models previously used to estimate WSIs may not be able to rigorously capture spatial and temporal variability at the sub-basin scale. These uncertainties may have implications for LCAs that account for water impacts of supply chains at regional or global scales.

References [1] Scherer et al, Large-Scale Hydrological Modeling for Calculating Water Stress Indices: Implications of Improved Spatiotemporal Resolution, Surface-Groundwater Differentiation, and Uncertainty Characterization, Environmental Science & Technology, 2015

16:30 Anne-Marie BoulayJane BareLorenzo BeniniMarkus BergerCecile BulleMichael LathuillièreAlessandro ManzardoManuele MargniMasaharu MotoshitaMontserrat NúñezTaikan OkiBradley RidouttSebastien Worbe and Stephan Pfister

New scarcity indicator from WULCA: consensus to assess potential user deprivation

ABSTRACT. The need for consensus-developed and recommended methods for water use impact assessment is clear in order to perform a water scarcity footprint consistently with ISO 14046:2014 and the challenge was undertaken by the WULCA working group, of the UNEP-SETAC Life Cycle Initiative. Including method developers and experts from different fields, the group is developing consensus-based indicators to assess impacts from water use, complying with the requirements of the ISO document. This work presents the results of the working group on the consensus method development. The work was divided in 6 parts:1) Identification of the question that the indicator should answer, 2) Identification of the modelling choices and possible options, 3) Consensus findings on each of these modelling choices, 4) Building of the resulting indicator(s), 5) Testing of the resulting indicator(s) and 6) Final recommendation. In order to answer these questions, a series of three expert workshops were held on three different continents: in Zurich (Switzerland), San Francisco (USA) and Tsukuba (Japan), with a total of 48 experts participating. The group agreed that the indicator chosen should answer the following question: “What is the potential of depriving another user of water in this region?”, independently of whether the user is human or ecosystem. Consensus finding of these modelling choices led to three possible indicators: 1) Demand-to-Availability ratio (DTA), 2) DTA*(Area/Availability)0.34 and 3) UWworld/UW (with UW referring to unused water, availability minus demand). Following a first testing phase and criteria analysis, a preliminary recommendation is made for the latter of these indicators. It is agreed that the final result will consist of a single metric covering the entire globe, modelled at various temporal and spatial scales for application in LCA with different inventory datasets. The group is proposing the result of its work and new consensus-based indicator with the hope that it will be adopted widely and hence decrease disparity and confusion when it comes to applying the new ISO standard on water footprinting, by providing an internationally approved, robust and simple indicator for assessment of potential impacts from water consumption.

16:45 Uta Krogmann and Kate Sullivan

Life-Cycle Assessment of Centralized versus On-Site In-Building Wastewater Treatment

ABSTRACT. Water scarcity has led to increased efforts to reduce residential water consumption. One measure is in-building wastewater treatment and reuse of water for toilet flushing and cooling towers. This raises two questions: what are the life-cycle environmental impacts of in-building wastewater treatment and reuse and their major contributors in an urban setting and how do on-site treatment systems compare to a centralized municipal system.

In this study, the life-cycle energy consumption and air emissions of water consumed daily in a residential green high-rise building in the Northeastern US with and without on-site wastewater treatment and in-building reuse were assessed by the Water-Energy Sustainability Tool (WEST) and the Wastewater-Energy Sustainability Tool (WWEST). Developed at the University of California at Berkeley, WEST and WWEST combine process-based and input-output based life-cycle assessment of the water supply and wastewater infrastructure and their operation.

Due to diseconomies of scale, the life-cycle energy consumption and release of greenhouse gas emissions of the on-site wastewater treatment facility exceeded those of the centralized system. Life-cycle energy and greenhouse gas savings from replacing potable water with reuse water were not enough to offset the increased energy and greenhouse gas emissions of the on-site wastewater treatment system. The contribution of potable water treatment and supply was not significant in the life-cycle for either scenario. The largest contributor to the impacts for both scenarios was the energy consumed during the operational phase while the impact of the construction phase varied. For the centralized scenario, the construction phase performed within the same order of magnitude as the operational phase, suggesting that its impact may be overlooked. For the on-site reuse scenario, construction was less significant, which is a potential benefit for on-site reuse if the operational energy consumption can be decreased. The neighborhood scale and the effect of the region other than the Northeastern US are still being assessed. A limitation of the study is life-cycle energy consumption, greenhouse gas emissions and major air emissions were included in this assessment.