Biogas Production from Surplus Plant Biomass Feedstock: Some Highlights of Indo-UK R&D Initiative

Abstract

Reliable supply of feedstock is one of the major factors accountable for acceptance and hence success of biogas technology. Cow dung (CD) has been the traditional feedstock for production of biogas which is utilized for domestic cooking in rural areas. Search for alternative feedstock becomes inevitable with increasing interest in biogas technology and prospect to extend its application up to power generation. Here, feasibility of two locally available surplus biomass viz., (i) Ipomoea carnea (IC) and (ii) rice straw (RS) were investigated for biogas production. Identified biomass was separately mixed with cow dung (in ratios of 40:60 and 60:40) and fed to 0.25 m3 commercial biogas reactors and 20 L batch biogas reactors. The work focused on biogas production potential, methane content and calorific value of biogas from the commercial biogas reactors. Biogas yield from the four treatments of different mixing ratios were compared with control i.e., CD as only feedstock. Both Ipomoea carnea and rice straw yielded more gas compared to the control. However, IC co-digested with CD yielded more biogas than rice straw co-digested samples (IC:CD::60:40 with 0.209 Nm3/kg volatile solid (VS) added per day and IC:CD:: 40:60 with 0.205 Nm3/kg VS added per day whereas, RS:CD::60:40 with 0.192 Nm3/kg VS added per day and RS:CD::40:60 with 0.190 Nm3/kg VS added per day). In addition, the work also focused on determination of the methane content of IC and RS co-digested biogas samples which were also more than the control.