Dealing with waste products and flows in life cycle assessment and emergy accounting: Methodological overview and synergies

Abstract

This paper considers the different approaches taken in dealing with waste products and flows in Life Cycle Assessment (LCA) and Emergy Accounting (EMA), from a methodological point of view, and aims to develop more standardized and synergistic procedures. LCA deals with the waste issue from the point of view of the impact of their disposal, as well as the potential benefit (‘environmental credit’) afforded by the avoided extraction and processing of additional primary resources when waste is recycled or its energy content recovered. The ‘environmental burden’ associated to the entire production and consumption chain leading to the waste item is generally not included in LCAs of waste management systems, due to the boundary being placed – consistently with the intended goal – around the actual disposal processes (including recycling alternatives and associated environmental credits). Instead, Emergy Accounting, a donor-side approach with its implicit boundary set at the biosphere level, in principle keeps track of the entire supply-chain at all times, considering even waste flows as products (or co-products), and calculating their intensity factors and assessing their role within the ecosystem's web and hierarchy. However, when the focus is limited to evaluating processes under human control, within the narrower space and time boundary of human-dominated production and consumption processes, waste products can arguably be regarded as something to be recycled or disposed of to minimize the environmental burden. When this is the case, and particularly in comparative analyses, the emergy perspective thus becomes closer to the LCA perspective and interesting methodological synergies may emerge. A clearly defined set of emergy algebra rules for waste products and flows, and specifically for recycling, was found to be still lacking in the available emergy literature. We propose here that a better and more consistent methodological solution may be arrived at by leveraging the work done in LCA.