Environmental sustainability of an integrate anaerobic digestion-composting treatment of food waste: Analysis of an Italian plant in the circular bioeconomy strategy

In light of the adoption of recent global policies and strategies for a more sustainable food waste management system and a greater control of environmental impacts, this study describes a circular bioeconomy plant model, currently operating in South Italy, for treatment and enhancement of organic fraction of municipal solid waste. The key basis for plant activity is dry anaerobic digestion of separately collected organic fraction of municipal solid waste (SC-OFMSW) followed by digestate composting process. Biomethane for use in the transport sector is obtained by biogas cleaning and upgrading, while high-quality compost for organic farming is produced by digestate composting. Plant activities are completed by the transformation of part of the produced waste into refuse derived fuel (RDF) to be allocated to waste-to-energy plants and the treatment of odour emissions which allows the recovery of ammonium sulphate as a fertilizer. A rooftop photovoltaic system supplies most of electric energy needed by the plant. For plant activities relative to 2020, carbon footprint was equal to -112 kg CO2eq. for Mg of organic waste, while depletion of fossil resources was estimated at -89.6 kg oil eq. Mg-1 of waste. Primary energy demand of food waste treatment system was -2.66 GJ Mg-1 of input waste. Replacement of natural gas with biomethane for transport sector provided the greatest improvement contribution for all the examined categories.