Comparative life cycle assessment of composting and anaerobic digestion technologies in the Greek context: Focus on energy and environmental impacts

This study compares composting and anaerobic digestion (AD) technologies for municipal solid waste (MSW) management in Greece using Life Cycle Assessment (LCA). The analysis evaluates the energy and environmental performance of both technologies, with and without biogas recovery, employing three impact-assessment methods: ILCD 2011 Midpoint+, Eco-indicator 99 (E), and ReCiPe 2016 Endpoint (E). Modeling was performed in OpenLCA 2.5 using the Ecoinvent v3.9 database, following ISO 14040/44 standards. Results show that composting causes substantially higher environmental burdens than AD in all methods and categories. According to ILCD, composting scored 5.47 × 10−5 species·year for ecosystem damage versus 1.96 × 10−10 for AD. Human-health impacts were also higher for composting (9.66 × 10−3 DALY, ILCD; 7.37 × 10−3 DALY, ReCiPe), except for Eco-indicator 99 (E), where AD with biogas recovery showed slightly greater impact due to system allocation. Regarding energy balance, AD without energy recovery has a higher energy demand than composting; however, AD with biogas utilization becomes energy-positive, producing more electricity and heat than it consumes and achieving a negative energy footprint. Overall, AD (particularly with biogas recovery) exhibits a markedly lower total environmental and energy footprint. Scaling up AD facilities under Greek conditions enhances sustainability and supports national waste-management goals and EU Circular Economy targets.