Summary
Power‐to‐gas technologies are considered to be part of the future energy system, but their viability and applicability need to be assessed. Therefore, models for the viability of farm‐scale bio‐power‐to‐methane supply chains to produce green gas were analysed in terms of levelised cost of energy, energy efficiency and saving of greenhouse gas emission. In bio‐power‐to‐methane, hydrogen from electrolysis driven by surplus renewable electricity and carbon dioxide from biogas are converted to methane by microbes in an ex situ trickle‐bed reactor. Such bio‐methanation could replace the current upgrading of biogas to green gas with membrane technology. Four scenarios were compared: a reference scenario without bio‐methanation (A), bio‐methanation (B), bio‐methanation combined with membrane upgrading (C) and the latter with use of renewable energy only (all‐green; D). The reference scenario (A) has the lowest costs for green gas production, but the bio‐methanation scenarios (B‐D) have higher energy efficiencies and environmental benefits. The higher costs of the bio‐methanation scenarios are largely due to electrolysis, whereas the environmental benefits are due to the use of renewable electricity. Only the all‐green scenario (D) meets the 2026 EU goal of 80% reduction of greenhouse gas emissions, but it would require a CO2 price of 200 € t−1 to achieve the levelised cost of energy of 65 €ct Nm−3 of the reference scenario. Inclusion of the intermittency of renewable energy in the scenarios substantially increases the costs. Further greening of the bio‐methanation supply chain and how intermittency is best taken into account need further investigation.