Synthetic methane: solid oxide electrolysis

Technology

What is it?

Methane is synthesised directly from steam and carbon dioxide gas in a solid oxide electrolysis cell at elevated temperatures.

Why is it important?

Methane can be synthesised directly from water and carbon dioxide, without requiring a precursory hydrogen production step. This reduces system complexity and could yield energy savings.

Characteristics

• Volumetric hydrogen density: Liquid state = ~100kg H₂/m³. At standard temperature and pressure = 0.7946g/100L
• Gravimetric hydrogen density: ~25% H₂ by weight
• Storage conditions: 90 to 120 bar

Benefits

• Single reactor means reduced system complexity and lower associated capital costs
• Allows integration of waste heat streams, reducing the required energy input
• Makes use of carbon dioxide as a process input

Limitations

• Balancing reactor temperature is a challenge. Methane product decomposition occurs at typical solid oxide cell operating temperature

RD&D priorities

• Improve catalyst selectivity
• Develop cell designs and electrolytes capable of operating at thermodynamically favourable conditions
• Understand fundamental reaction mechanisms

Known active organisations

• CSIRO