Techno-Economic Assessment of Biohydrogen Production from Dark Fermentation of Wastewater Sludge

Abstract

This paper explores a simulation model for biohydrogen production by dark fermentation of wastewater sludge using the Aspen Plus process simulation software. The process includes sludge pretreatment, hydrolysis, fermentation and post-treatment of the products though separation and purification. The outcomes of the model serve as inputs for a techno-economic analysis to assess the economic viability of the process. Additionally, a sensitivity analysis is employed to scrutinize the influence of crucial variables on the overall process. Finally, a greenhouse gas emission potential of the proposed system was obtained from literature, to ensure the environmental benefits from this process. The cost analysis for 23 ton/day sludge processing capacity dark fermentation plant showed a biohydrogen production cost of $11.4/kg of hydrogen produce. The capital cost and the labor cost have been the key contributors to the production cost. The biohydrogen price decreased to $5.9/ kg when the plant was scaled up to 500 ton/day capacity. Examining the greenhouse gas (GHG) emission potential of the process from literature unveiled a substantial reduction in GHG emissions and a carbon credit of $90/ ton CO2-eq can lower the biohydrogen production price to $1.28/kg, rendering it competitive to hydrogen price produced from natural gas-based technology.