Batch anaerobic co-digestion of proteins and carbohydrates

Batch anaerobic studies were conducted using five mixtures (M1–M5) of bovine serum albumin (BSA) and starch. The results showed that co-digestion of BSA and starch had a positive impact on the methane production. The highest methane production of 288 mL, the highest methane yield of 360 mL CH4/g CODadded, and the highest maximum methane production rate of 62 mL CH4/d were achieved for M4 (20% BSA and 80% starch). Most of the particulate proteins (90%) as well as particulate carbohydrates (95%) were degraded in the first 3 days. The hydrolysis coefficients of particulate proteins and particulate carbohydrates ranged from 0.65 to 1.01 d−1 and from 0.53 to 1.06 d−1, respectively. The highest methane production was achieved at C:N ratio of 12.8 for M4. For BSA only, propionic acid was the main volatile fatty acid (VFA), while for the starch only, butyric acid was the predominant VFA.