Thermophilic anaerobic digestion of sugar beet tailings.

摘要

Tailings from sugar beet processing are currently managed by landfilling or land application. As an alternative option, beet tailings were anaerobically digested at thermophilic temp. It was found that tailings contain a large fraction of water-soluble organic matter and approx. 0.6 chemical O2 demand per g volatile solids (VS) that inhibited initiation of methanogenesis. Methanogenesis could be initiated if the solubilized material was removed. By using a process that involves leaching and removal of solubilized matter followed by flooding the bed with digested leachate containing acclimatized inoculum, anaerobic digestion of tailings was successfully accomplished. Most of the methane potential remaining in solids was generated within 1 wk. Methane yield of tailings was estimated to be 295 l at standard temp. and pressure per kg VS, of which 50-60% was from the readily solubilized organic matter. A volume reduction of 70-80% was achieved and approx. 60% of DM and 75% of volatile solids were degraded. All volatile organic acids (acetic, propionic, butyric) after an initial accumulation were degraded to low levels in all experiments. Individually, 53.3% of crude protein, 88.3% of nonfibrous carbohydrates, 81% of hemicellulose, 31.5% of lignin and 64.6% of cellulose were either degraded or solubilized. It was also shown that a robust inoculum for sustained thermophilic anaerobic digestion can be cultured by initially flooding a bed of tailings with a buffer solution. The inoculum developed was robust enough to carry out successive balanced digestions of several batches of tailings.