A Comparison of Performance between Two Anaerobic Biodigesters Configurations for Biogas Production

Abstract

A comparison of performance was made for the two most common anaerobic biodigesters existing configuration to date, continuously stirred tank biodigester (CSTBR) and plug-flow biodigester (PFBR) to produce biogas and electricity by anaerobic digestion using as feedstock dairy manure feasible for application in rural areas of Latin America to generate renewable energy as electricity and liquid fertilizer, while reducing animal wastewater pollution, greenhouse gases, and odor. The two configuration CSTBR and PFBR systems were installed at bench scale by using dairy manure as feedstock. The results showed that under the same operation conditions HRT 1 day and OLR 19.4 g COD/L day the CSTBR produced more biogas (1.0 L/L d), methane (0.8 L/L d) than the PFBR corresponding values were biogas (0.8 L/L d), methane (0.6 L/L d), and removed more organic matter, 12% COD, 8.7% VS than did the PFBR, 11.5% COD, 8.1% VS. The performance resulted similar when the HRT was increased to 3 days and the OLR decreased to 9.8 g COD/L day. The microbial communities between the CSTBR and PFBR configurations were performed by using pyrosequencing molecular technique. The microbial communities are highly variable with the distribution and abundance of taxonomic groups differing between the samples taken from the two AD configuration systems, more richness of archaeal microbial diversity were present in the PFBR whereas higher bacterial microbial diversity were present in the CSTBR sample. It is recommended the application of CSTBR configuration for AD. However, the PFBR configuration can be improved by intermittent mixing application, that failure because of clogging of solids due to long HRT and SRT, particularly for small PFBR installed in developing countries.