Carbon capture, utilisation and storage in the energy transition

CCUS has a vital, albeit limited, role to play in delivering a net-zero economy by mid-century alongside zero-carbon electricity and clean hydrogen.

Mike Hemsley
Deputy Director, Energy Transitions Commission

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Article Summary

Even with the most ambitious possible reductions in gross emissions, it is almost certain that cumulative CO2 emissions between now and 2050 will exceed the 'carbon budget' consistent with a 1.5°C climate objective. With clean electricity delivering 65-70% of the world's final energy demand, accompanied by a significant role for low-carbon hydrogen, and a modest role for sustainable, low-carbon bioresources, the capture of 7 GtCO2/year by 2050 will still be required, from 0.04 GtCO2/year today, and equivalent to around 20% of CO2 emissions from the world's energy system today. Carbon capture, utilisation and storage (CCUS) must therefore play three vital but limited roles in the energy transition:
- To decarbonise those sectors where alternatives are technically limited (i.e. industrial processes which by their nature produce CO2, such as cement)
- To deliver some of the CO2 removals required to achieve global climate objectives
- To provide a low-cost decarbonisation solution in some sectors and geographies where CCUS is economically advantaged relative to other decarbonisation vectors locally

The Energy Transitions Commission (ETC) recently completed its Making Mission Possible series of reports demonstrating that it is possible to achieve faster reductions in emissions than seemed feasible a decade ago, including in harder-to-abate sectors driven by clean electricity, low-carbon hydrogen and sustainable bioresources. This article summarises some key messages from the latest report, CCUS in the Energy Transition: Vital but Limited, which assesses the roles CCUS should play on the path to net zero and what action is required by governments, corporate, and finance to achieve it. The full report is available to download for free from www.energy-transitions.org

Supporting role of CCUS in decarbonisation pathways
The need for CCUS depends on the cost and availability of alternative decarbonisation technologies. ~7-10 GtCO2/year of carbon capture is likely to be required by 2050, of which around 65% relates to non-fossil fuel sources of CO2 such as cement process emissions, bioenergy with carbon capture and storage (BECCS), and direct air capture (DAC). The other 35% - around 2.5-4.0 GtCO2/year - would allow a significant but dramatically reduced scale of fossil fuel use (for example, around 10 Mb/d and 2,700 billion cubic metres (BCM) of gas, 90% and 30% below today's levels) to be compatible with achieving a zero-carbon economy.

Technological feasibility and carbon removal potential
The CCUS value chain can be considered in four stages — source, capture, transport, and end of life — which can entail either storage or use.

Capture The majority of CCUS costs occur in the CO2 capture stage and typically reflect CO2 concentration. Different sector applications present different concentration levels, varying from over 95% for coal-to-chemical processes to 0.04% for DAC (reflecting the concentration of CO2 in the atmosphere).

Over the last 10 to 15 years, there has been only a limited reduction in carbon capture costs, unlike in solar PV panels, wind turbines, batteries, and (more recently) electrolysers, where dramatic cost reductions have been achieved. As a result, the cost competitiveness of other decarbonisation vectors has significantly improved relative to CCUS. The costs of applying CCUS in many applications are still considered cost-effective, though significant future cost reductions are likely to be limited. In the case of DAC, however, improvements in energy efficiency and reductions in Capex costs driven by technology improvements and scale effects are expected to reduce costs from around $450/tCO2 today to below $100/tCO2 in advantaged regions by 2050.

Transport CO2 can be transported safely and at a low cost via pipeline, truck, or ship. The majority of transported CO2 is likely to be transferred via onshore and offshore pipelines.

Storage At end-of-life, CO2 can be permanently stored or used in products, materials, or fuels. Global theoretical geological storage volumes are vast and exist in nearly all regions. Potential storage volumes have been estimated at exceeding 10,000 GtCO2, which would be enough to store today's total annual CO2 emissions (circa 40 Gt) each year for more than 250 years.

Where available, storage costs are, on average, $10-20 per tonne, which is typically cheaper than utilising CO2 instead of storing it.
Importance of the source of CO2

The ultimate carbon balance of capturing, utilising, and storing CO2 will depend on the source of CO2 and the duration of its storage and/or utilisation.

The capture of CO2 from fossil fuel combustion or industrial processes can result in sector decarbonisation if the CO2 is stored or used in long-term applications such as construction aggregates. It can increase carbon efficiency if CO2 is used for short-term applications (for example, to produce a synthetic fuel product), but it will never result in net carbon removal.

In contrast, if CO2 is captured via photosynthesis or DAC and either stored or permanently used, it can generate net carbon removal. Any public policies that support CCUS, and all carbon accounting for CCUS, must therefore be based on a rigorous assessment of the carbon effect, combining both sources and end-of-life outcomes.

Carbon storage can be safe and permanent with strict regulation
Storage can be safe and permanent, provided it is well managed and strongly regulated. This is achieved through a series of manmade and natural factors, which act as barriers preventing leakage:
- Artificial measures include plugging injection wells with steel and concrete seals; natural factors relate to CO2 being injected under a cap rock which acts as a barrier to release; over time, the CO2 is dissolved in brine or physically absorbed into rock pores.
-  Although manmade storage sites have not been in operation long enough to prove their capacity to permanently trap CO2 naturally occurring subterranean stores of CO2 have remained trapped for thousands of years. This is further supported by real-world evidence from existing CCS facilities running since the 1990s and from academic studies of the technical feasibility.

Theoretically, there is a risk that CO2 injected underground may leak out of the reservoir through naturally occurring pathways (such as faults) or via manmade pathways (such as faulty wells). CO2 leaks will only be minimised if strong regulation is enforced. Oil and gas companies have experience in drilling, pumping, simulation of geological behaviours, and well management, which means the expertise required to inject and store CO2 underground is already available. Strong safety and regulatory regimes will need to be put in place to ensure the risk of accidental leaks is limited, with parties held accountable when managing large volumes of CO2.

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