Environmental and economic impacts of improper materials in the recycling of separated collected food waste through anaerobic digestion and composting

Separately collected food waste (SC-FW) is effectively recycled through industrial anaerobic digestion (AD) and composting. However, the presence of improper materials in SC-FW not only generates technical problems to AD and composting, but also lowers the quality of the outputs of the processes. As a consequence, improper materials found in SC-FW cause not negligible environmental and economic burdens.In this study, the environmental and economic impacts due to the presence of unsuitable materials in the SC-FW, de-termined through compositional analysis, were estimated through life cycle assessment and environmental life cycle costing approaches. Three different scenarios were analysed for both AD and composting processes: (i) the current sit-uation (CS); (ii) the improved scenario (AS) with an amount of improper materials in SC-FW reduced to 3 % (w/w); (iii) the ideal scenario (IS) with the total absence of foreign materials.Environmental benefits were determined for the AS and IS scenarios in 17 of the 19 analysed impact categories. Con-sidering the GHG emissions, higher savings were measured for AD in AS and IS scenarios (47 % and 79%, respectively) than in CS scenario. Similarly, savings of -10.4 kg fossil oil eq/tonSC-FW (AS) and - 17.1 kg fossil oil eq/tonSC-FW (IS) for AD could be obtained with respect to the CS scenario. Greater economic benefits were calculated for AD (-76.4 euro/ tonSC-FW) and composting (-52.2 euro/tonSC-FW) in the IS scenario. Savings up to euro 2,249,780 and euro 3,888,760 could have been obtained in 2022 by reducing to 3 % (w/w) and eliminating, respectively, the amount of improper materials in the SC-FW.