Characterization and Dilution of Sheep Manure for Optimization of Biogas Production

This study investigated the suitability of sheep manure for biogas production by optimization of the biogas yield and methane content at different manure-to-water dilution ratios. Sheep manure contained 35.77% dry matter, 64.23% moisture, 15.95% ash, 7.62% acid-insoluble ash, 84.05% organic matter, 48.75% organic carbon and C:N (carbon-to-nitrogen) ratio of 30.09: 1. It contained a gross energy of 4421.75 kcal/kg, 7.80 pH, 621.00 ppm total dissolved solids and an electrical conductivity of 1.25 mS/cm. Fibre analysis of sheep manure revealed 29.23% cellulose, 19.94% hemicellulose and 16.74% lignin. Nutrient analysis showed 9.36% crude protein, 2.34% ether extract and 1.62% total nitrogen. In sheep manure, mineral concentrations were 83.84 ppm zinc, 31.08 ppm copper, 116.49 ppm manganese, 757.72 ppm iron, 1.24%calcium, 0.20% sodium, 0.43% potassium and 0.77% phosphorus. Biogas production at manure-to-water dilution ratios of 1:2, 1:3 and 1:4 was 0.289, 0.260 and 0.255 Nm³/kg TS, respectively. The corresponding methane content in the biogas was 54.06, 55.54 and 53.72%. The findings suggested that sheep manure is a renewable source of bio-energy and a manure-to-water dilution ratio of 1:2 provides the most effective balance for maximizing biogas yield.