Techno-Economic Analysis and Life Cycle Assessment of the Biogas Extraction and Upgrading from Lake Kivu

Abstract

Various biogas upgrading technologies are currently used to remove CO2 and increase biomethane purity. Water scrubbing is the only method used in current Lake Kivu projects, where captured CO2 and H2S are reinjected into the bottom of the biozone, with CO2 eventually being released into the atmosphere. Additionally, the potential impact of H2S flux into the biozone on oxygen depletion needs to be considered. Amine scrubbing offers an alternative approach to biogas upgrading, potentially addressing environmental concerns associated with the current method while enabling the use of captured CO2. We estimate and compare the investment costs and environmental footprints of water and amine scrubbing, utilizing a blend of methyldiethanolamine and monoethanolamine. Our results indicate that the carbon-removal cost for amine scrubbing is more than twice that for water scrubbing. However, integrating waste heat recovery into amine scrubbing reduces CO2 capture costs by 30%. Furthermore, under the current study’s assumption, GHG emissions can be reduced by up to 70% by implementing amine scrubbing. The results reveal that the heat requirement in amine scrubbing presents a significant challenge. Steam generation via waste heat recovery is a critical factor influencing economic and environmental outcomes.