An evaluation of upstream assumptions in food-waste life cycle assessments.

Abstract

The aim of this paper was to evaluate the tenability of the “zero burden assumption” for a waste stream with an economic value. Thirty comparative life cycle assessments (LCAs) addressing food-waste treatment were analysed and five questions were asked: (i) was the “zero burden assumption” used and what percentage of the waste system environmental impact was contributed by food-waste production? (ii) was there any indication that the waste had economic value? (iii) was it a comparative study? (iv) was the approach different between peer reviewed journals and commercial studies? and (v) if an environmental burden were assigned to the waste in each study, how might it be estimated? It was evident that the upstream ‘zero burden assumption’ is commonly followed in food waste LCA and no quantitative environmental impact is associated with the food waste resource, be it a comparative study or not. Few studies acknowledged that waste has an economic value. The argument for including the environmental impact of food waste and waste in general was reasoned on two fronts. Firstly, it was shown that the environmental impact of the waste itself may hold a large percentage of the overall system impact and should therefore be included. Secondly, with the valorisation of waste and its subsequent use as a feedstock in other systems that produce a product with an economic value, it is no longer directed to a biosphere sink, and should therefore not be called a waste as it stays in the technosphere as a resource. Future food-waste and waste LCA in general could follow the approach that was explored and quantify the environmental impact of waste by using a ‘meta-waste-based accounting’ approach.