Use of Agricultural Residues of Rice Straw and Sheep Manure as Substrates for Biogas Production by Anaerobic Co-Digestion

Agricultural activities related to rice processing and sheep farming generate solid waste such as rice straw, and manure that can be processed to generate renewable energy. An efficient way to transform this waste into biogas and methane is efficient through anaerobic co-digestion, which represents a viable alternative for energy production. The objective of this research was to produce biogas with potential methane content, through the anaerobic co-digestion of rice straw (RS) residues, which provide carbon, and sheep manure (SM), which mainly provides nitrogen. The methodology included the physicochemical characterization of the substrates, followed by the pretreatment of the rice straw in alkaline sodium hydroxide solution (8 and 10%) in order to optimize the co-digestion process during 15 days. The doses of manure applied in co-digestion in relation to rice straw were 0%, 30%, 50%, 70% and 100%. Under these conditions, completely random combinations were made with 56 experimental units for the determination of the biochemical potential, which lasted 15 days. Biogas measurement was performed by volume displacement. The results indicated that a mixture of 50% pretreatment of the RS was more efficient than the other mixtures, with a maximum accumulated production of 1801 mL of total biogas. The technique of pretreatment of lignocellulosic substrates is appropriate in the processes of co-digestion of agricultural waste for the generation of biogas.