Circularity of water - good for conscience or the environment? A deeper look into the water footprint of factories.

Abstract

Water plays an indispensable role in factories and is needed for a diversity of purposes. The circular use of water is an often-found approach nowadays which refers to the multiple internal recycling of water in factories before releasing it back to the environment. The intention behind that is clear and good – but the question is whether this is actually beneficial from an environmental perspective? This paper aims at providing a more detailed look into that important topic while analyzing efforts and benefits of water circularity. A generic life cycle assessment (LCA) model is presented and different industrial related scenarios serve as a base for deriving deeper and transferable insights into environmentally sustainable water management in factories. For the target objective water consumption, the recycling rate is of limited relevance as it only influences water use (withdrawal) but not the decisive evaporation rate. In a similar way, freshwater deprivation impacts resulting from water consumption (evaporation) depend on the location of the factory and the local scarcity – but not on recycling rates. Also for the global warming potential (GWP), the recycling rate is of limited relevance, as waste water treatment (WWT) is the decisive factor here. In cases in which the internal WWT causes more environmental efforts than municipal WWT and in which a relevant share of water is withdrawn from groundwater, an increasing recycling rate can reduce the depletion of groundwater resources – but causes higher carbon emissions. Depending on local scarcity and carbon intensity of electricity mixes, this can be justified but trade-offs need to be considered.