Composting food waste or digestate? Characteristics, statistical and life cycle assessment study based on an Italian composting plant

Abstract

Agricultural use of food waste compost is the natural way to return nutrients to the soil. In application of the European waste hierarchy, the recovery of nutrients from food waste through composting is a more preferable option than incineration or disposal. Two different inputs are generally used for industrial composting processes: food waste as it is or digestate resulting from the anaerobic digestion of food waste. In this study, a life cycle assessment (LCA) analysis was performed for the production of compost from both organic fraction of municipal solid waste (OFMSW) and OFMSW-based digestate, processed by an Italian composting plant. The environmental footprint of the production of the two types of compost was determined by quantifying 19 impact categories. The treatment of OFMSW through anaerobic digestion prior to composting resulted more beneficial to the environment than direct composting of the feedstock. Indeed, OFMSW compost showed greater environmental impacts than digestate compost for 17 out of 19 categories. Savings were measured in 18 and 10 impact categories for digestate and OFMSW compost, respectively. In particular, for the climate change category, a total net saving of −12 kg and −434 kg of CO2 equivalent was measured for the production of 1 Mg of OFMSW and digestate compost, respectively. The reported results were obtained using only real plant data and compared with various literature LCA analyses. The chemical-physical characteristics of the two types of compost were also compared and subjected to principal component analysis.