Promoting energy recovery from recalcitrant agro-industrial wastes through anaerobic digestion: A review on olive mill residues

Energy production from agro-industrial residues is a continuously expanding sector, due to high organic waste availability and the needs of finding new low cost and environmentally clean energy sources. Direct anaerobic digestion of such as residual biomasses is often hindered by the occurrence of inhibition processes. Nutrients addition, pH correction, thermal pretreatment or co-digestion are different effective options that can be adopted to increase process performances. Up to 2.4 m3 CH4 m-3 day-1 can be generated from the mono digestion of pure olive mill waste, while pretreatment and co-digestion can increase productivity up to 60% and 97%, with respect to the standard conditions.