CCS is a proven technology, which has been used in heavy industry and the oil and gas sector for decades, however it has yet to be deployed on an industrial level in the UK and total global capacity is currently only 40Mt/yr, mostly from projects which utilise CO2 from a single source for the purposes of oil recovery. The Net Zero scenario envisages the UK along capturing and storing four times that amount, from diverse sources and not always with the economic benefit which drives enhanced oil recovery.
There are three technology areas required for CCS - CO2 capture, transportation and storage.
There are three methods of CO2 capture: post-combustion, pre-combustion and oxy fuel combustion.
- Post-combustion involves scrubbing the CO2 from flue gases released during the combustion process.
- Pre-combustion uses a gasification (solid fuel) or reforming (gaseous fuel) process, followed by CO2 separation to yield a hydrogen-rich fuel gas.
- Oxy fuel combustion involves combusting fuel in recycled fuel has enriched with oxygen to produce a CO2-rich gas.
Capture processes vary from well proven with decades of experience to developmental. Given the key role CCS will play in the Net Zero scenario, we expect significant process development in the future. The concept of ‘clustering’ CO2 from multiple and varied sources implies that multiple carbon capture technologies will be used.
The technological aspects of CO2 transport, compression, buffer storage and pipeline transport are all well understood and established technologies. The major impediment to increased CO2 transportation is the financing and contractual framework required for the increased infrastructure required.
CO2 can be permanently stored deep underground in geological formations. In the UK these are located offshore in either saline formations or depleted oil and gas reservoirs. Enough storage locations have already been identified in the UK to last approximately 100 years.