Turning captured CO2 into products
Captured CO2 can be converted into a variety of products through chemical processes that combine CO2 with other inputs like hydrogen, heat, or catalysts. This approach can create market value from captured carbon and reduce reliance on fossil feedstocks.
Common conversion pathways
- Electrochemical reduction: using electricity (often from renewables) and catalysts to reduce CO2 into chemicals like carbon monoxide (CO), formic acid, or hydrocarbons.
- Thermochemical processes: reacting CO2 with hydrogen or other reagents at high temperatures to produce fuels such as methanol, methane, or synthetic hydrocarbons.
- Mineralization: reacting CO2 with minerals or industrial waste to form stable carbonates used in construction materials.
- Biological processes: engineered microbes can convert CO2 into compounds like oils, proteins, or specialty chemicals.
Examples of CO2-derived products
- E-fuels: synthetic gasoline, diesel, or jet fuel made by combining CO2-derived syngas with hydrogen.
- Chemicals: methanol, which can serve as a fuel or chemical feedstock, and urea for fertilizers.
- Building materials: CO2-cured concrete and aggregates that store CO2 permanently.
Challenges and energy needs
- Hydrogen requirement: many CO2 conversion processes need low-carbon hydrogen; producing that hydrogen adds to energy demand.
- Energy intensity: converting CO2 to high-energy-density products consumes substantial energy, which must be low-carbon for net climate benefit.
- Cost and scale: many conversion routes are currently more costly than conventional production and need scale-up and technology improvements.
Environmental considerations
Lifecycle analysis is crucial. Products that re-release CO2 when used (like synthetic fuels) can still yield climate benefits if produced with renewable energy and used in hard-to-decarbonize sectors, or if they replace more carbon-intensive alternatives. Permanently sequestering CO2 via mineralization offers clearer climate advantages.
Summary
Captured CO2 can become fuels, chemicals, and construction materials through several chemical and biological routes. Success depends on low-carbon energy supply, the availability of hydrogen, and market demand for low-carbon products.