Greenhouse gas emission of household plastic biogas digester using life cycle assessment approach

Abstract

Biogas is one of renewable energy sources capable to reduce greenhouse gas (GHG) emission. Plastic biogas digester is a popular type adopted by people due to its low cost and simplicity. The utilization of materials for digester fabrication, however, positively contributes to GHG emission. The purpose of this research is to evaluate GHG emission of household scale plastic biogas digester by using life cycle assessment (LCA) approach. The boundary system consists of fabrication of the digester, operation and maintenance, and utilization of the biogas. The research is conducted by making an inventory to collect related information on the quantity of materials utilized to construct a household size plastic biogas digester along with emission factor of each material. Other important parameters include biogas yield and its methane content. Emission reduction is calculated from LPG saving due biogas utilization to fuel kitchen stove. Result showed that a household size plastic tube biogas digester system potentially reduced GHG emission by 1400.78 kg CO2eq/year for a five years of service life time. The GHG emission (in kg CO2eq/year) is comprised of 59.11 for digester construction, 7.83 for biogas production, (-456.14 for biogas utilization, and -1011.58 for slurry digestate utilization.