Environmental Assessment of Wastewater Treatment and Reuse for Irrigation: A Mini-Review of LCA Studies

This paper provides an overview of existing LCA literature analyzing the environmental impacts of wastewater treatment and reuses, with irrigation as a process or scenario. Fifty-nine (n = 59) papers published between 2010 and 2022 were reviewed to provide insights into the methodological choices (goals, geographical scope, functional units, system boundaries, life cycle impact assessment (LCIA) procedures). The results show that LCA research has steadily increased in the last six years. The LCAs are case-study specific, apply a process perspective, and are primarily conducted by European authors. The LCAs are mainly midpoint-oriented with global warming, acidification and eutrophication potential as the most common impact categories reported. Volumetric-based functional units are the most widely applied. The most commonly used LCIA models were ReCiPe and CML, with Ecoinvent as the most commonly used database and SimaPro as the primary LCA software tool. Despite the fact that these methods cover a wide range of midpoint impact categories, nearly half of the studies focused on a few life cycle impact category indicators. In many studies, the LCA scope is frequently narrowed, and the assessment does not look at the cradle-to-grave system boundary but rather at cradle-to-gate or gate-to-gate system boundaries. Regardless of technology or other system boundary assumptions, the design of environmentally efficient wastewater reuse schemes is primarily determined by the type of energy supplied to the product's life cycle. Our findings highlight that more holistic studies that take into account the expansion of system boundaries and the use of a broad set of environmental impact categories, supported by uncertainty and/or sensitivity analysis, are required. The overview presented in this paper serves as groundwork for future LCA studies in the field of irrigation with treated wastewater.