High-solids anaerobic digestion of cassava pulp in semi-continuous bioreactors

• Published in: Bioresources Vol. 16; no. 4; pp. 6723 - 6736
• Main Authors: Zhao, Wei, Zhou, Chen-Yu, Zhang, Jun, Wang, Dun-Qiu
• Format: Journal Article
• Language: English
• Published: Raleigh North Carolina State University 01.11.2021
• Subjects: Acidification; Anaerobic conditions; Anaerobic digestion; Biodegradation; Biogas; Bioreactors; Cassava; Enzymes; Inoculum; Loading rate; Manures; Nitrogen; Organic matter; Pulp; Sewage sludge; Sludge; Volatile solids; China
• ISSN: 1930-2126; 1930-2126
• DOI: 10.15376/biores.16.4.6723-6736

The effects of two total solids contents (TS) and two inocula were studied for the semi-continuous high-solids anaerobic digestion (HS-AD) of cassava pulp under mesophilic conditions (35 ± 2 °C). In the 1.0-L bioreactors, two TS of 15% and 20% with digestate as a sole inoculum were chosen to run the HS-AD, and two inocula (the digestate from the AD of cassava pulp and sewage sludge) were used separately under TS 20%. All treatments were carried out at the organic matter loading rates (OLRs) of from 3.0 to 10.0 kg volatile solids (VS)/(m3·d), with each phase of 6 days followed by two 3-days phases of no feeding and then low OLR of 6.5 kg VS/(m3·d). Compared with TS 15%, the bioreactors of TS 20% with the digestate had a higher buffering capability to alleviate the rapid acidification and a higher level of the specific methane yields (SMYs) of from 0.212 to 0.233 m3/(kgVSadded) at the OLRs of 4.0 to 6.5 kgVS/(m3·d), while TS 15% obtained the highest SMY of from 0.152 to 0.182 m3/(kgVSadded) at the OLR of 4.0, 6.5, and 8.0 kgVS/(m3·d). In contrast, sewage sludge did not restrain the rapid acidification and only yielded quite small SMYs under TS 20%.