Plausibility of assessing environmental impacts of a domestic biogas digester in the design stage

The construction of biogas system involves anthropogenic activities, which can have negative effects on the ecosystem. Environmental impact assessment of the biogas system at subsystem level before manufacture fosters design optimization. This minimizes environmental pollutants associated with the system during operation. In this study, a gate-to-gate life cycle assessment (LCA) of a domestic biogas digester at the design stage was performed. The biogas digester, which is to operate at mesophilic conditions with a functional unit of 24,900.3 kWh/10 years was investigated, and its anticipated outputs during operation were presented. The environmental processes investigated include the transportation of components, the digester manufacturing, the digester operations, and the recyclability and disposal of the digester after its useful life. Results showed that equipment manufacturing and transportation of components are of high environmental influence on the particulate matter deposit measuring 0.00493 ppm and 0.00932 ppm, respectively. However, the manufacturing process produces higher toxic waste (8.6 m³) than the transportation process (1.15 m³). More harmful than carbon dioxide in climate change is methane gas during biogas plant operation. As part of the measures to reduce environmental impacts around the product system, optimization of transportation trips is recommended. The use of mechanical seal, as opposed to the conventional rubber seal, is preferred to prevent methane leakage during the system operation. Integrating LCA studies at the early design stage of equipment enables informed decisions prior to equipment fabrication.