Captured carbon dioxide can be used either directly or it may undergo various biological or chemical processes prior to being used as a raw material or ingredient in the manufacture of various products (Carbon Capture and Utilization, CCU). Currently, according to the International Energy Agency (IEA), about 230 million tonnes of carbon dioxide are directly utilized worldwide every year. Almost 130 million tonnes are used to make synthetic urea for fertilizers. Oil companies inject an estimated 80 million tonnes into the subsurface in order to extract oil reserves more quickly and as completely as possible (Enhanced Oil Recovery, EOR). The remaining carbon dioxide is utilized in the food and beverage industries or is pumped into greenhouses to enhance plant growth. Carbon dioxide can also be used as an extinguishing agent or refrigerant.
There are some relatively new proposals to use captured carbon dioxide as a carbon source in the production of synthetic fuels for ships and aircraft, for carbon-based feedstocks in chemical industry, or for plastics and construction materials. If these prove to be feasible on a large scale, products containing carbon from captured carbon dioxide could replace materials formerly made from fossil-sourced carbon. The ultimate goal of these ideas would be to establish an added-value chain and circular economy for carbon, in which carbon from coal, oil or natural gas is no longer needed.
For the production of chemicals and fuels from carbon dioxide, the gas must be synthesized with hydrogen. In this way, methanol and other hydrocarbons can be produced that will ultimately be useful in chemical industry or as synthetic fuels. A pilot project for this purpose is being planned at a refinery in Schleswig-Holstein, for example. If chemical industry implements the CCU projects it has already announced, the sector could see an estimated five million tonnes of captured carbon dioxide being used worldwide for fuel production in 2030. However, almost half of the proposed projects are still in the early development stage, and in many locations the pipelines and other infrastructures for transporting hydrogen and carbon dioxide are not yet in place.
fig. 8.11 > Captured carbon dioxide, and particularly the carbon it contains, can be used in a large variety of applications. However, to achieve a positive climate effect, the gas or carbon must be processed in such a way that it can no longer escape into the atmosphere.