Carbon dioxide: Production route
Why fertiliser plants are the cheapest CO2 source
What this tab covers How it is made: the main production routes or, for product families, the main product types and technologies, compared on share of supply, inputs per tonne, plant scale, yield, co-products and unit cost.CO2 for sale is almost always a by-product. The cheapest sources are streams that are already nearly pure: ammonia and hydrogen plants, ethanol fermentation, gas processing that strips CO2 from raw natural gas, and natural CO2 wells. Dilute sources such as boiler flue gas need chemical capture, which costs much more. Supply therefore depends on fertiliser, ethanol and gas industry economics, not on CO2 demand.
Routes compared
| Route | Share of supply | Inputs per tonne | Typical scale | Yield | Co-products | Unit cost |
|---|---|---|---|---|---|---|
| Recovery from ammonia and hydrogen plants | main merchant source in Europe and India (indicative); all urea CO2 | about 100-150 kWh per t for compression, purification and liquefaction (indicative) | 100-1,000 t a day; Billingham 750 t a day | near complete recovery of the process stream | none | not published; cheap while the ammonia plant runs, unavailable when it stops |
| Fermentation CO2 (bioethanol, breweries) | main US merchant source (indicative) | about 100-150 kWh per t (indicative) | 100-1,000 t a day | high | none | not published |
| Natural CO2 wells and gas processing | most US EOR CO2 (indicative) | compression power only | Mt a year per source | not applicable | none | not published |
| Post-combustion and direct air capture | small | about 2.5-4 GJ heat per t CO2 for amine capture (indicative) | Indian examples include small plants at Tuticorin (Carbon Clean, about 60,000 t a year for soda ash, indicative) | about 90% capture | none | about $50-100/t from flue gas; several hundred dollars per t for direct air capture (indicative) |
How each route works
Recovery from ammonia and hydrogen plantsThe reformer's shift gas is scrubbed with amine or hot potassium carbonate, giving a CO2 stream of about 98-99%. Part goes to the urea plant; surplus is compressed, purified and liquefied for sale.
Cheapest high-purity source; supply fails when gas prices close ammonia plants.
The Chemical Engineer (Oct 2021); indicative energy Fermentation CO2 (bioethanol, breweries)Yeast fermentation releases nearly pure CO2, about 0.95 t per t of ethanol. It is scrubbed, dried and liquefied. Ensus at Wilton can meet up to 40% of UK CO2 needs.
Biogenic and steady; seasonal with ethanol margins.
The Chemical Engineer (Oct 2021); stoichiometry Natural CO2 wells and gas processingUS domes such as McElmo and Bravo supply EOR by pipeline. Gas processing plants remove CO2 from raw gas; some inject it (Sleipner, Gorgon) or sell it.
Large and cheap; natural-well CO2 adds to atmospheric CO2 when used for EOR.
IEA (2019, indicative) Post-combustion and direct air captureAmine solvents capture CO2 from flue gas at 5-15% concentration; direct air capture works at 0.04%. Energy for solvent regeneration dominates cost.
Unlimited sources; much costlier than by-product CO2.
indicative Unit economics are indicative ranges from the sources named; costs move with feedstock and energy prices, plant size and region.