Globally, there is a growing effort to offset the cost associated with CCUS. Apart from geological carbon storage there is a developing interest in finding commercially viable opportunities for utilising the captured CO2.
At a small scale, CO2 is widely used in a range of commercial applications, ranging from the building industry (synthetic cements, strengthening concrete), the food industry (carbonating beverages and refrigeration), agriculture (enhancing plant growth in greenhouses), to firefighting (fire suppression, extinguishers) and manufacturing (inerting agent in electronics and semi-conductors).
Most of the anthropogenic CO2 released into the atmosphere is generated by combustion of fuels for energy production, including coal, petroleum, methane, biomass and bio-derived liquid fuels. The hydrocarbons are combusted to provide energy for transportation, electricity and heat. The anthropogenic CO2 molecule which is a product of combustion is therefore at a low energetic state. Converting the CO2 for instance by chemical or biological conversion into other products requires vast amounts of energy. This limits the opportunity to cost-effectively utilise CO2, constraining the potential for CO2 utilisation to comprise more than a small fraction of the CO2 emitted from energy usage each year.
However, there are some areas in which carbon dioxide can be re-used or recycled commercially. The most common is to use CO2 for enhanced hydrocarbon recovery – whether oil or gas – to boost the amount of oil (or gas) recovered. Oil fields that have supplied crude oil for decades, eventually slow down and produce less each year. However, a large amount of oil remains trapped in the pores of the rock – this can be extracted using enhanced oil recovery techniques.
CO2-Enhanced Oil Recovery (EOR)
CO2-EOR involves the injection of compressed carbon dioxide into an oil or gas reservoir. The CO2 acts like a solvent and causes the oil to expand and flow more easily to production wells. In CO2-EOR, a large portion of the injected CO2 remains below the ground. If the CO2 that returns to the surface is separated and reinjected to form a closed loop, this results in permanent CO2 storage.
Research by Imperial College demonstrates that, CO2-EOR can be optimised to store 1t of CO2 per 1.1bbls of oil produced. Assuming 0.43t CO2 emission per bbl of oil consumption (EPA GHG calculator, 2017), this results in a net negative emission of 0.52t of CO2 per bbl of oil produced through CO2-EOR.
EOR has been used for decades in the United States. CO2CRC is currently working with partners to examine the feasibility of using CO2 in EOR in Australia.
Carbon dioxide can also be used as a feedstock for new products. In this process the CO2 is reintroduced into the production process and treated as a carbon resource, rather than a post process emission. The three major processes are biological CO2 transformation by microbes and bacteria into new organic compounds, the chemical transformation for building blocks in the chemical industry or synthetic fuels in the transport sector, and the production of synthetic building materials through CO2 mineralisation.