Optimizing hydrogen and e-methanol production through Power-to-X integration in biogas plants

Abstract

The European Union's strategy for achieving net zero emissions heavily depends on the development of hydrogen and e-/bio-fuel infrastructure and economy. These fuels are poised to play a critical role, functioning both as energy carriers and balancing agents for the inherent variability of renewable energy sources. Large-scale production will necessitate additional renewable capacity, and various Power-to-X (PtX) concepts are emerging in countries with significant renewable potential. However, sourcing renewable carbon presents a significant challenge in scaling the production of carbon-based e-fuels, and this is anticipated to become a limiting factor in the future. This investigation examines the concept of a PtX hub that sources renewable CO₂ from modern biogas plants, integrating renewable energy, hydrogen production, and methanol synthesis at a single site. This concept facilitates an internal, behind-the-meter market for energy and material flows, balanced by an interface with the external energy system. The size and operation of all plants comprising the PtX hub were co-optimized, considering various levels of integration with surrounding energy systems, including the potential establishment of a local hydrogen grid. The levelized costs of hydrogen and e-methanol were estimated for a site commencing operation in 2030, taking into consideration the recent legislation about renewable fuels of non-biological origin (RFNBOs). Our findings indicate that, in its optimal configuration, the PtX hub relies almost exclusively on on-site renewable energy, selling excess electricity to the grid for balancing purposes. The connection to a local hydrogen grid facilitates smoother PtX process operations, while the behind-the-meter market reduces energy prices, providing a buffer against external market variability. The results demonstrate the feasibility of achieving a levelized cost of methanol below 650 € /t and hydrogen production costs below 3 €/kg in 2030. In comparison, a standalone e-methanol plant would incur a 23% higher cost. The ratio of CO₂ recovered to methanol produced was identified as a critical technical parameter, with recovery rates exceeding 90% necessitating substantial investments in CO₂ and H₂ storage. Overall, our findings support the planning of PtX infrastructures that consider integration with the agricultural sector as a cost-effective pathway to access renewable carbon resources.