Making synthetic fuels from CO2 and hydrogen
Synthetic fuels combine carbon from CO2 with hydrogen to create hydrocarbons that mimic conventional fuels. The process typically relies on low-carbon hydrogen (from electrolysis) and captured CO2 from industrial sources or direct air capture.
Steps in production
- Low-carbon hydrogen production: electrolysis separates water into hydrogen and oxygen using renewable electricity.
- CO2 capture: CO2 is sourced from point sources, industrial streams, or direct air capture.
- Conversion into syngas: CO2 and hydrogen are converted into synthesis gas (a mix of CO and H2) using processes like reverse water-gas shift.
- Synthesis: Fischer-Tropsch or methanol synthesis converts syngas into liquid hydrocarbons or alcohols.
- Refining: products are upgraded, blended, and treated to meet fuel specifications for transport or industry.
Types of synthetic fuels
- Synthetic gasoline and diesel: hydrocarbons with energy density and combustion properties similar to conventional fuels.
- Synthetic jet fuel: kerosene-type products tailored for aviation standards.
- Methanol and methane: alternative fuel forms useful in shipping, chemical production, or as gas replacements.
Advantages and challenges
- Advantages: compatibility with existing engines and infrastructure, and the potential for deep emissions cuts when produced with renewable energy and captured CO2.
- Challenges: high energy and capital requirements, the need for abundant low-carbon electricity, and currently higher costs than fossil fuels.
Lifecycle considerations
Net climate benefits depend on the carbon intensity of the electricity and the source of CO2. When renewable power and low-carbon CO2 are used, synthetic fuels can offer significant emissions reductions, especially in sectors that lack alternatives.