Life cycle assessment of environmental impacts for two-stage anaerobic biogas plant between commercial and pilot scales

Abstract

This study presents the detailed life cycle assessment (LCA) of environmental impact potential for two-stage anaerobic biogas plants between commercial and pilot scales. It provides a comprehensive and systematic approach to evaluating the environmental impacts of producing biogas from livestock wastes in several phases: collecting, processing, and production. The commercial biogas plant (C-BP) system is located in Central Taiwan's pig farm, with 1500–2000 pigs a year. The Symnergy (symbiosis bioenergy model) biogas pilot plant (S-BP) is installed in Manado City, Indonesia. The Institute of Green Products, Feng Chia University, designed both C-BP and S-BP systems. The environmental impacts of both systems' gate-to-grave life cycles were assessed and compared using Simapro 9.0.0 software. The pilot-scale biogas plants produce bioenergy from the wastewater of the slaughterhouse. Therefore, 10,950 tonne/year of slurry feedstock flowing into the commercial biogas plant was considered a functional unit equal to 21 times larger than the pilot scale biogas plant. The LCA analyzes the impacts of three processes for feedstock collection, biogas production, and digestate production. It was found that Photochemical Ozone Creation Potential had the highest total impact on C-BP (33%), and Eutrophication had the highest impact on S-BP (33%). Both the biogas production systems of C-BP and S-BP showed very low environmental impacts, and the impacts of C-BP are lower than the S-BP. However, implementing digesters considerably reduced the potential environmental impacts of well manure feedstock handling and fertilizer applications. The LCA analysis among the three individual processes is developed to allow critical points and environmental impacts for local government. Consequently, the LCA report could help establish regional sustainability strategies for the management of livestock wastes by anaerobic two-stage biogas plant from manure.