Anaerobic Co-Digestion of Swine Manure and Corn Stover for Biogas Production

摘要

Anaerobic co-digestion of swine manure and corn stover for biogas production has been studied in two completely-mixed and semi-continuously fed reactors (Reactor 1 and Reactor 2). Each reactor had a working volume of 14 liters and was operated at 35°C, a hydraulic retention time of 25 days, and an agitation speed of 120 rpm. Initially the reactors were operated as duplicates and each was fed with 560 ml of swine wastewater per day. After a stable performance had been achieved in both reactors with almost the same results, corn stover was added to Reactor 2 to get a Carbon to Nitrogen ratio (C:N) of 10:1. Since then 560 ml of swine wastewater and 14 g of corn stover have been added to Reactor 2 every day to keep the C:N ratio at 10:1. In the meantime Reactor 1 has been fed the same as previously. Removal of chemical oxygen demand (COD), total kjeldahl nitrogen (TKN), fixed suspended solids (FSS), and volatile suspended solids (VSS) was 52%, 1%, 54%, and 55%, respectively in Reactor 1. When corn stover was added to Reactor 2, removal of COD, TKN, FSS, and VSS was 53%, 11%, 58%, and 59%, respectively. There was also a reduction of NH_4-N by 15% in Reactor 2, probably because of the better balance of nutrients compared to Reactor 1, where an increaseof ammonium was detected. Average gas production was 274 ml per day in Reactor 1 and 3,910 ml per day in Reactor 2. Gas chromatography (GC) analyses have shown that methane content is 67.8% in Reactor 1 and 50.7% in Reactor 2. Methane yield in Reactor 1and Reactor 2 was 0.22 and 0.18 m3 of CH_4 per kg of COD removed, respectively. Preliminary results indicate that corn stover could be substantially degraded to methane in an anaerobic co-digestion with swine manure.