Renewable hydrogen and methane production from microalgae: A techno-economic and life cycle assessment study

Abstract

Microalgae is a potential candidate to produce renewable fuels. However, current gasification technologies are limited due to char- and tar-accumulation in the gasifier. We have reported a single step, tar-free catalytic reactive flash volatilisation (RFV) of microalgae to produce hydrogen or methane. In this work, the experimental results were used to develop a detailed ASPEN PLUS® flowsheet model to perform techno-economic assessment of hydrogen and methane production. A plant located in India, processing 12790 kg/h of microalgae to produce 1239 kg/h of H2 or 3484.96 kg/h of CH4 was considered. Process scale-up and heat integration principles were used to generate relevant data. Simultaneously, the experimental and simulation data are used to perform life cycle assessment (LCA). The results indicated that the payback period for hydrogen production was 3.78 years with 22% of IRR. Moreover, the life cycle climate change impact was 7.56 kg CO2 eq./kg H2 produced, which was 36.47% lower than the steam reforming of methane. Methane production was not economically feasible. However, it was environmentally preferred with the life cycle climate change impact of 1.18 kg CO2 eq./kg CH4 produced. Sensitivity analysis was performed to identify opportunities to achieve further reduction in costs and life cycle impacts. It was observed that the payback period was more sensitive to feedstock cost compared to other parameters. 25% increase in the feedstock cost resulted into 35.38% increase in the payback period.