Anaerobic digestion of mechanically sorted organic waste: The influence of storage time on the energetic potential

The separate collection is the privileged practice to manage municipal solid waste (MSW) in order to meet the more and more ambitious recovery targets enforced by legislation. Nevertheless, considerable amounts of unsorted MSW are still produced at European level and mechanical biological treatments (MBTs) are widely spread to pursue their valorization. Most MBT plants rely on aerobic biostabilization methods, whose product cannot be qualified as compost and raises the issue of its fate. Anaerobic digestion is an interesting option to treat mechanically selected organic waste, but its feasibility may be limited by the prolonged storage time of this kind of waste. This study evaluated the variation of the energetic potential of the organic fraction mechanically sorted from MSW deposited for different periods. Results showed that such potential decreased by 46% after only 3 days storage and further reduction was observed with increasing the deposit time. Experimental outcomes allowed the identification of an inverse relation between methane production and deposit time and addressed the proposal of a simplified approach to estimate the maximum storage period to take the greatest advantage from the anaerobic treatment of mechanically sorted organic waste.