BIOENERGY FROM GREEN WASTE THROUGH ANAEROBIC DIGESTION: SUBSTRATE, BIOGAS, AND DIGESTATE CHARACTERISATION AT LAB-SCALE

The green waste (GW), generated from private and public gardens, represents a noticeable stream of the organic fraction of municipal waste (OFMW). At the Italian level, the GW quantitative stream is mainly addressed to composting, instead of being valorise through anaerobic digestion (AD) to recover bioenergy as renewable source. On the other hand, the biogas production through AD poses some technical issues, such as the detailed knowledge and comprehension of the biogas composition and its evolution during the AD process; and the consideration of the characteristics of the substrate and digestate in the overall evaluation of the AD process. In view of these concerns, a biochemical methane potential (BMP) experiment was conducted on GW as substrate in mesophilic conditions at lab-scale. Detailed physico-chemical characterisations of the substrate, inoculum, and digestate were performed, in addition to the ultimate analysis on the GW. Moreover, biogas samples were periodically collected from the headspace of one of the digesters containing the substrate-inoculum mixture for the subsequent chemical characterisation. The findings of this experimental study would allow to better understand the mutual relations among substrate physico-chemical characteristics, AD process and biogas composition evolution, and digestate physico-chemical characteristics