Small-Scale Hybrid Methanol–Methane Production Based on Biogas: Stochastic Sensitivity Analysis of the Economic Sustainability

This study investigates the economic viability at the pre-feasibility level of a hybrid methanol and biomethane plant based on biogas coupled to a photovoltaic (PV) power plant and a proton exchange membrane (PEM) electrolyzer. The reference case settled in Uganda consisted of two units powered by a 200 kW PV plant and grid power: a 25 Nm3/h anaerobic digester and a 140 kW PEM electrolyzer-based methanol plant. Its production of 33.3 tons of methanol and 70.1 tons of biomethane per year can provide cooking fuel for 750 households. Response Surface Methodology was used to evaluate the impact of the three main factors on the simple payback period (PBP). The size of the PV plant had the most significant impact on PBP, followed by the cost of electricity, the interaction between these factors, and the PEM electrolyzer capital cost reduction, in this contribution order. These findings point to energy generation costs as the primary factor affecting the economic viability of these small-scale designs, even more than the PEM’s capital cost. The response surface analysis revealed that only in a reduced region of the design space are values found that meet the threshold of 10 years for plant economic viability.