Methanol from biogas via solid oxide electrolyzer cell technology: a techno-economic study on a novel process configuration

Methanol is a key platform chemical and energy carrier with a rapidly growing global demand; however, its conventional production relies heavily on fossil-based feedstocks, contributing substantially to greenhouse gas emissions. This thesis proposes and evaluates a novel, integrated biogas-to-methanol process designed to mitigate this environmental impact. The proposed configuration integrates oxy-combustion of biogas, a combined heat and power (CHP) unit, and high-temperature co-electrolysis of steam and carbon dioxide in a Solid Oxide Electrolysis Cell (SOEC), followed by catalytic methanol synthesis and multi-stage purification. The energy analysis demonstrates that strategic heat integration allows the plant to achieve full thermal self-sufficiency, eliminating the need for external steam utilities. Nevertheless, the process is fundamentally electricity-intensive due to the high energy requirement of SOEC, resulting in a significant net electricity demand of over 6.6 MWh /tonne of methanol produced. The detailed economic assessment, based on Capital Expenditure (CAPEX) of €35.4 million and Operating Expenditure (OPEX) of €28.9 million/year, reveals that the process is not financially viable under current market conditions, yielding a highly negative Net Present Value (NPV) of -€103.6 million in the baseline Italian case study. The environmental evaluation further highlights that the process's carbon footprint is critically dependent on the carbon intensity of the grid electricity. For the Italian scenario, the process exhibits a carbon intensity of +1.05 tonnes of CO₂ equivalent per tonne of methanol, offering only marginal improvement over conventional natural gas reforming. A carbon-negative footprint is achievable only in regions with access to near-zero-carbon electricity. Despite these economic challenges, a comparative analysis confirms that the SOEC-based configuration is technologically and economically superior to a similar process employing a conventional Alkaline Water Electrolysis (AWE) unit, primarily due to the SOEC's higher electrical efficiency. This work, therefore, contributes a robust techno-economic analysis of a promising pathway for sustainable methanol production, concluding that while the proposed process is technically feasible, its viability is contingent upon significant shifts in energy markets and policy. The findings underscore that fundamental process energy efficiency remains the most critical parameter driving both the economic and environmental performance of Power-to-X technologies.