Catherine Raptis

Water in life cycle assessment—50th Swiss Discussion Forum on Life Cycle Assessment—Zürich, 4 December 2012

Water use, its impacts and management, have become a focus of attention in the past decade in the context of climate change and increasing consumption (in particular of food and agricultural products) due to a growing global population. Many efforts have been made to include water-related issues in life cycle assessment (LCA) in various ways, from the long-standing eutrophication, acidification, and ecotoxicity methods, to the more recent water consumption aspects. Four years on from the first discussion forum on water in LCA (35th Swiss Discussion Forum on LCA, Zürich, 5 June 2008), numerous developments have occurred, resulting in a rich palette of approaches. Significant challenges still remain, related to the complexity of water systems and ecosystems, and certain impacts are still not considered. New challenges have emerged, such as how to fit these “pieces” together to form a coherent and comprehensive approach for assessing the impacts of water use (both degradative and consumptive). Practice has started to apply certain water consumption-related approaches and an early feedback between practitioners and developers is essential to ensure a harmonious further development. The 50th Swiss Discussion Forum on Life Cycle Assessment (DF-50) gave a brief overview of the current status of water use in LCA, and then focused on the following topics in three main sessions: (1) a selection of recent research developments in the field of impact assessment modeling; (2) identification of new and remaining challenges where future effort could be concentrated, with a focus on spatial and temporal resolution; (3) and experiences and learnings from application in practice. Furthermore, several short presentations addressed the issues of inventory requirements and comparison of impact assessment approaches. The DF-50 was concluded with a discussion workshop, focusing on four issues: which degree of regionalization is desirable, how to address data gaps in inventories, the comparability of different impact assessment approaches, and the pros and cons of including positive impacts (benefits). Numerous recent developments in life cycle impact assessment have tackled impact pathways, spatial and temporal resolutions, and uncertainties. They have lead to an increase of the completeness of impact assessment, but also of its complexity. Although developments have also occurred in inventories, the gap between impact assessment and inventory is challenging, which in turn limits the applicability of the methods. Regionalization is confirmed as an essential aspect in water footprinting; however, its implementation requires concerted effort by impact assessment developers and software developers. Therefore, even though immense progress has been made, it may be time to think of putting the pieces together in order to simplify the applicability of these tools: enabling the support of improvements in companies and policy is the ultimate goal of LCA. The recordings and presentations of the DF-50 are available for download from www.lcaforum.ch.

Global thermal pollution of rivers from thermoelectric power plants

Worldwide riverine thermal pollution patterns were investigated by combining mean annual heat rejection rates from power plants with once-through cooling systems with the global hydrological-water temperature model variable infiltration capacity (VIC)-RBM. The model simulates both streamflow and water temperature on 0.5° ×0.5° spatial resolution worldwide and by capturing their effect, identifies multiple thermal pollution hotspots. The Mississippi receives the highest total amount of heat emissions (62% and 28% of which come from coal-fuelled and nuclear power plants, respectively) and presents the highest number of instances where the commonly set 3 °C temperature increase limit is equalled or exceeded. The Rhine receives 20% of the thermal emissions compared to the Mississippi (predominantly due to nuclear power plants), but is the thermally most polluted basin in relation to the total flow per watershed, with one third of its total flow experiencing a temperature increase ≥5 °C on average over the year. In other smaller basins in Europe, such as the Weser and the Po, the share of the total streamflow with a temperature increase ≥3 °C goes up to 49% and 81%, respectively, during July-September. As the first global analysis of its kind, this work points towards areas of high riverine thermal pollution, where temporally finer thermal emission data could be coupled with a spatially finer model to better investigate water temperature increase and its effect on aquatic ecosystems.

Assessing the environmental impacts of freshwater thermal pollution from global power generation in LCA

Freshwater heat emissions from power plants with once-through cooling systems constitute one of many environmental pressures related to the thermoelectric power industry. The objective of this work was to obtain high resolution, operational characterization factors (CF) for the impact of heat emissions on ecosystem quality, and carry out a comprehensive, spatially, temporally and technologically differentiated damage-based environmental assessment of global freshwater thermal pollution. The aggregation of CFs on a watershed level results in 12.5% lower annual impacts globally and even smaller differences for the most crucial watersheds and months, so watershed level CFs are recommended when the exact emission site within the basin is unknown. Long-range impacts account for almost 90% of the total global impacts. The Great Lakes, several Mississippi subbasins, the Danube, and the Yangtze are among the most thermally impacted watersheds globally, receiving heat emissions from predominantly coal-fuelled and nuclear power plants. Globally, over 80% of the global annual impacts come from power plants constructed during or before the 1980s. While the impact-weighted mean age of the power plants in the Mississippi ranges from 38 to 51years, in Chinese watersheds including the Yangtze, the equivalent range is only 15 to 22years, reflecting a stark contrast in thermal pollution mitigation approaches. With relatively high shares of total capacity from power plants with once-through freshwater cooling, and tracing a large part of the Danube, 1kWh of net electricity mix is the most impactful in Hungary, Bulgaria and Serbia. Monthly CFs are provided on a grid cell level and on a watershed level for use in Life Cycle Assessment. The impacts per generating unit are also provided, as part of our effort to make available a global dataset of thermoelectric power plant emissions and impacts.