Analysis of Agricultural Substrates for Nutritive Values and Biomethane Potential

Bio-methane from agricultural waste has enough potential to compete with other sources of energy. This study aims to examine the bio-methane potential of numerous agricultural wastes, including cotton waste, wheat bran, lentil straw, barley straw, rice bran and peanut peels straw with the aim to produce renewable energy and solve waste disposal issues. The proximate, ultimate and chemical composition analyses were performed to predict the theoretical biomethane potentials in silico. However, the potential was experimentally assayed at mesophilic conditions. Moreover, elemental and lignin based biodegradability of substrates have also been determined. The methane contents in biogas are in the range 57–64% and the yield varied from 216.3 (barley straw) to 317.6 (cotton waste) ml/g volatile solids. These results indicate that higher biodegradability of substrates resulted in higher methane production. The prediction of bio-methane potential from chemical composition, elemental composition and organic fraction were not as fit accurately as being assessed for methane potential. It merely provided the extent of biodegradability. During digestion, volatile fatty acids were produced, viz. acetic acid (58–63%), butyric acid (28–32%), propionic acid (6–13%) and converted into methane but limited concentrations of intermediate acids indicated similar microbial consortium in all digestions. Hence, it was also concluded that the lignin and hemicellulose content played a limiting role in digestion and posed negative impact on biogas production.