Assessing the food recovery hierarchy concept from an eMergy accounting perspective: Validation and theoretical insights

The food recovery hierarchy (FRH) is an important concept widely used worldwide as a guideline for food waste management policies. It consists of different options for food waste management hierarchically organized, in which source reduction is the most preferable option, followed by food donation, feeding animals, industrial use, composting, energy recovery, and landfilling. The most common approaches used in the literature to validate the FRH concept consider both, a user-side and donor-side perspectives. While the former are typical of methods such as life cycle assessment and ecological footprint that are extensively explored in the literature, the latter is typical of methods such as eMergy accounting (EMA), a perspective that remains unexplored. This study aims to overcome that literature gap by discussing: (i) The validity of FRH concept under an EMA perspective; (ii) The differences on saving natural resources depending on the adopted FRH option; (iii) Obtaining a mathematical model representing the saved emergy as a function of invested emergy. Results show that the FRH is confirmed under the EMA lens as expressed by the proposed emergy return index (ERI). The most preferable options within FRH are by far more efficient in saving emergy than the least preferable options (about 250 times better). The obtained model EMS=2.44E+22/EMI ^0.51 describes the relation between the invested and saved emergy along the FRH hierarchy. Insights are presented to promote discussions on existing ERIs cluster within the FRH.