Electrolysis-enhanced co-digestion of switchgrass and cow manure

BACKGROUNDAnaerobic digestion of agricultural wastes is a cost effective way for combining resource recovery and methane production. This paper evaluates the co-digestion of cow manure and switchgrass in a completely stirred tank reactor (CSTR) by the electrolysis-enhanced anaerobic digestion (eAD) process. RESULTSThe electrodes for water electrolysis were installed directly in an anaerobic digester and were used to create micro-aerobic conditions. Significant gains in process performance and biogas quality were obtained at current densities of 20-25 mA L-R(-1) (per digester volume) with a corresponding volumetric energy consumption of 0.07-0.08 Wh L-R(-1). In particular, the COD removal rate was increased from 0.6 to 0.9 g COD L-R(-1) d(-1), methane production increased by 26%, and H2S content in the biogas declined from 2500-3000 ppm to less than 10 ppm. CONCLUSIONSThe improved performance was achieved due to methane production from hydrolytic H-2 and possibly due to the enhanced hydrolysis of organic matter. (c) 2013 Her Majesty the Queen in Right of Canada Journal of Chemical Technology & Biotechnology (c) 2013 Society of Chemical Industry