Leaf litter biogas digester residue—A nutrient supplement for mushroom cultivation

Abstract

Partially digested biogas digester residues (BDR) arising from leaf litter/agro-residues fed biogas plants (typically used as fertilizer) were tried and tested as a substrate for mushroom cultivation. Such digested residues are outputs of emerging MSW and peri-urban biomethanation plants and can greatly create value addition and increase economic sustainability of the overall MSW treatment systems. Low-value agro-residues such as sugarcane trash, groundnut husk, and sorghum stalk were substituted with 30% BDR and used as substrate for cultivation of Pleurotus florida and Pleurotus djamor. The biological efficiency, yield, and nutritional value achieved with these substrates were studied. The most suitable substrate that produced higher yields and biological efficiency was sorghum stalk mixed with BDR (2 kg/kg substrate). Addition of BDR with agro-residues could increase mushroom yield by 17–20% and reduce growth stages by 3–5d. Anaerobic digestion of biomass removes >60% of carbohydrates as gas while conserving the NPK in the BDR. BDR rich in N was also increased the protein content of both P. florida and P. djamor by 7–12%.