Ozonolysis and Enzymatic Pretreatment of Fallen Norway Maple (Acer platanoides L.) Leaves for Anaerobic Digestion

Fallen leaves of Norway maple (Acer platanoides L.) were evaluated as a lignocellulosic substrate for anaerobic digestion (AD). The aim was to identify the pretreatment variant that maximizes methane yield. Leaves were milled and dry sieved, and two particle size classes were selected. The 1–2 cm fraction underwent chemical pretreatment by ozonation only, whereas the 0.5–1 cm fraction was first ozonated and then subjected to biological pretreatment with stepwise dosing of an enzymatic preparation. Ozonation conditions were varied with respect to particle size, ozone concentration (O3), gas flow rate, and contact time. Reducing the particle size from 1–2 cm to 0.5–1 cm increased the cumulative biogas yield by 9.7% (from 64.73 to 71.01 mL g−1 VS) and the methane yield by 13.6% (from 42.01 to 47.75 mL g−1 VS) relative to the control. These findings indicate that particle size reduction combined with ozonation and staged enzymatic dosing is a promising route to improve biomethane recovery from autumn leaf feedstocks.