Life cycle analysis of incineration compared to anaerobic digestion followed by composting for managing organic waste: the influence of system components for an Italian district

The benefits and environmental burden of two different strategies (incineration vs anaerobic digestion followed by composting) to manage the organic fraction of municipal solid waste were assessed. Particular attention was also focused on system components, including collection, treatment, facility construction, and disposal, as well as the effect of the energetic context. Source segregation intensities considered for the scenario with incineration and with anaerobic digestion followed by composting were respectively of 0 and 52 %. The analysis was performed by an LCA approach, and the impact was assessed by the CML method. The functional unit was a single ton of organic waste generated in the area considered. System boundaries were expanded to include the differences in waste collection and multi-functionality waste treatments. Existing databases were retrieved, also adopting experimental data for the waste management area considered. Overall, the scenario with the highest rate of source segregation of organic waste, using anaerobic digestion followed by composting, gave a lower impact for human and terrestrial toxicity. Concerning the other impacts, incineration gave the maximum benefits. The impact of anaerobic digestion and composting arises mainly from energy consumption, greenhouse gas emissions (i.e., N2O, VOC), and landfilling of residues. The sensitivity analysis performed by varying the energetic mix of the context confirmed the advantages of incineration of the organic fraction. Incineration of organic waste leads to maximum environmental benefits compared to anaerobic digestion and composting. Furthermore, anaerobic digestion and composting was characterized by high gaseous emissions with high greenhouse gas potential even if the production of organic fertilizer gave some benefits concerning the avoided exploitation of mineral resources. The impact due to the collection phase and facility construction was quite limited and in some cases negligible.