Revisiting mass, economic value, quality-based functional units in life cycle assessment of foods towards environmental benchmarking

Climate change is the big challenge, which definitely calls for a sustainable product declaration by life cycle assessment (LCA). In the recent years, a variety of functional units (FUs) have been applied to the comparative LCAs of product systems, but a persistent methodological challenge of applying FUs is still posed, especially in food systems. Responding to the research question of which FU is appropriate for proper environmental benchmarking, this present study revisits mass, economic value, and multiple (caloric value, protein, carbohydrate, fibre, saturated fat, minerals, vitamins) quality-based 12 FUs in food LCAs. Carbon footprints of 20 food products, expressed as Global Warming Potential 100, are calculated by openLCA 1.10.3 software, which are considered in the correlation test between the indicators per FUs using the statistical analysis, R 3.6.1. The results indicate that although the mass-based FUs (on dry/wet basis) do not reflect the actual function of food products, the FUs might be applied to the environmental benchmarking since both the FUs have a good correlation with others (R = 0.7-0.9) and vice versa, especially with the economic value-based FU to be integrated quantity & quality into a single FU. The results also reveal that it could be inappropriate to define a quality-based FU using all of macro & micro nutrients and minerals (R = 0.1-0.5), and the multiple quality-based FUs might not be appropriate for the environmental benchmarking. The comprehensive investigation of FUs for food LCAs could provide valuable insights into environmental benchmarking suitability.