Development and evaluation of household biogas plant with twin digesters in series

Abstract

The study was conducted at PMAS-Arid Agriculture University Rawalpindi Pakistan to compare the biogas production from fresh material digester (FMD) and slurry feeding digester (SFD). The small biogas household plant was consisted of two digesters first Fresh Material Digester (FMD) and second Slurry Fed Digester (SFD) in series. The small size biogas plant was constructed with concrete rings available in the market instead of bricks and cement. The volume of each fermentation chamber is 9.2 m3 and the construction cost of this biogas plant is Rs. 50000. The household plant fulfills the cooking requirement of 3-4 family members. Three different treatments of feeding materials i.e buffalo dung (BD), buffalo dung plus sheep waste (BD+SW),buffalo dung plus chicken droppings (BD+CD) were studied. The highest biogas productions were recorded 0.46 m3/day, 0.51m3/day and 0.50m3/day from BD, BD+CD and BD+SW treatments, respectively in FMD. The highest biogas production in SFD was recorded 0.31 m3/day, 0.33m3/day and 0.34 m3/day from BD, BD+CD and BD+SW treatments respectively. The SFD gave enough gas production that was 45% of the FMD. Thus by increasing the retention time of feeding doze in the construction of 2nd plant in series, the production of gas can be doubled.