Biogas Production from Chinese Herb-extraction Residues: Influence of Biomass Composition on Methane Yield

The Chinese traditional medicine industry is developing quickly in China, and there is a growing demand for the reasonable treatment of Chinese herb-extraction residues (CHER) that are generated during the process of preparing such medicines. Different from other biomass materials, the nutrient composition of CHER discharged from different producers may vary widely, which makes the study of CHER recycling quite difficult. The present study concerns the effect of nutrient composition on the specific methane yield from the anaerobic digestion of CHER in batch trials under mesophilic temperatures. Large differences were found in the nutrient compositions of the six kinds of CHER, and the total fat and neutral detergent fiber contents affected the specific methane yield more significantly than did the total protein and total sugar contents. The specific methane yields of the six kinds of CHER were 199, 208, 211, 144, 151, and 201 mL CH4 per gram of volatile solids. From the digestion experiments, a multiple linear regression equation, the Methane Energy Value Model (MEVM), was derived; this model estimates the methane yield from the nutrient composition of CHER. The model requires further validation and refinement.