Enhanced Biogas Production Using High-Density Polyethene Digester Insulated with Saw Dust

Abstract This study was carried out to investigate the production of biogas by the anaerobic digestion of cow dung using doubled high-density polyethene digester (HDPE) drum insulated with sawdust. The key objectives of this paper is firstly to develop a suitable heat capacity bio-digester made of doubled high density polyethene drum (30L fabricated into 60L) using sawdust (as doubled drum space filler) to further stabilize the slurry temperature, and secondly to remove the biogas generated impurities using optimal scrubbing method. The developed doubled high-density polyethene digester (HDPE) drum was charged with 10kg of cow dung mixed with 20L of water in a ratio of 1:2. The digestion process was performed in two different types; doubled high-density polyethene bio-digester with no sawdust and doubled high-density polyethene bio-digester with sawdust. Biogas production started on the 2nd day after charging when performance test was carried out in two different types; pre-scrubbing (with and without sawdust) and post-scrubbing (with and without sawdust) using optimal scrubbing method of steel wool (500g) + lime (500g) and lime (500g) + water (1L). The results showed that a maximum percentage CH4 yield of 65%, 60%, 52% and 48% were obtained in the 24th day for doubled high-density polyethene bio-digester (sawdust and scrubbed), doubled high-density polyethene bio-digester (sawdust and unscrubbed), doubled high-density polyethene bio-digester (no sawdust and scrubbed) and doubled high-density polyethene bio-digester (no sawdust and unscrubbed) respectively. Similarly, a maximum percentage reduction of CO2 level and H2S level at 8% and 0.5%, 30% and 8%, 9% and 0.5%, 40% and 8% were obtained in the 24th day for doubled high-density polyethene bio-digester (sawdust and scrubbed), doubled high-density polyethene bio-digester (sawdust and unscrubbed), doubled high-density polyethene bio-digester (no sawdust and scrubbed), and doubled high-density polyethene bio-digester (no sawdust and unscrubbed) respectively. This result showed that insulation of the surface doubled high-density polyethene bio-digester improved CH4 yield to 65% and reduced impurities effect of CO2 level to 75% and H2S level to 92%.