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Revising the Role of Groundwater in Life Cycle Assessment

Final Report Summary - GWAT-LCA (Revising the role of groundwater in life cycle assessment)

Life Cycle Assessment (LCA) is a modular procedure to quantify and compare the environmental burdens of any product, service, or good. It is based on ISO standards (ISO 14040 series), and involves sequential procedures such as 'goal and scope definition', 'inventory analysis' (LCI), 'impact assessment' (LCIA) and 'interpretation'. The purpose is to fully examine the environmental burdens or benefits, that is, those that stem from the entire life cycle of a product, from cradle-to-grave. For example, a bottle of wine would not only be characterised by the net water in the bottle, but all the water that is spent for grapevine irrigation, grape-crushing, as well as water that is consumed for glass production, bottling, transport and all the effects from recycling and disposal. LCA follows a holistic paradigm, often at the expense of accurate estimations. This fact does not necessarily mean a disadvantage, as it gives LCA the space to perform a combined investigation of multiple different safeguard subjects and assessment criteria. These are distinguished by different standard impact categories such as global warming, ozone depletion, land use, depletion of natural resources, and toxic effects. The normative values that reflect the impacts within each category are scientifically based, but often have to be understood as rough reference figures for comparative assessment. This is due to the specific assumptions for calculating indicators and their commonly approximate nature.

Compared to standard impact categories within LCA, water is special. In contrast to other abiotic resources such as coal or crude oil, it can be replenished. In contrast to CO2 emissions, there exists an immense spatial dependency of impacts on natural water bodies. Total global freshwater resources are sufficient, but not evenly distributed and often scarce in regions of high demand. Natural resources are difficult to assess if their value is not just local (e.g. on a community or industry scale), but on a societal level (like health effects). Setting up functional relationships in order to derive a generally valid and practicable evaluation is tedious due to the complex, insufficiently understood, and uncertain natural processes involved. This is also true for those effects and processes connected to natural water, or more particular, groundwater systems.

Consequently, one overarching goal here is to identify requirements of LCA procedures in relation to hydrogeology if groundwater is to be properly integrated. The result is a conceptual framework, which extends beyond a streamlined screening LCA. It is intended as an initiative leading to more sophisticated and robust LCA applications, which realise the existence and nature of the different hydrological compartments. Emphasis is placed on the 'safeguard environment groundwater', both with respect to its central role for human and ecological users and its role as receptor.

As a focal point, we concentrate on the most water consumptive sector, agriculture, and show how to compile the water-efficiency of cropping and regional water availability. As an illustrative example, global wheat farming is chosen, as wheat is one of the crops with the greatest acreage worldwide. Additionally, global water and groundwater use for more than 120 crops is assessed on a high spatial resolution. The regionalisation procedure is implemented as versatile Matlab/GIS model.

Furthermore, as second focus, we selected shallow geothermal energy use, related legal issues as well as technical, hydrogeological and environmental effects. Detailed modelling studies on natural heat transport at the land surface are presented, as well as new simulation techniques for closed-system ground source heat pumps (GSHPs). A comprehensive LCA of environmental impacts from GSHPs is published that reveals the dominant role of (primary) resource use, greenhouse gas emissions and particle matter formation related to power supply for the heat pump.