Global CO2 storage capacity is much lower than previous industry estimates and should not be treated as a limitless commodity to help meet climate targets, according to a study published on 3 September by scientific journal Nature.
Global CO2 capacity is estimated at around 1.46 trillion t of CO2, and this could run out as early as 2200, according to the study led by the International Institute for Applied Systems Analysis. This is only a tenth of industry estimates of around 14 trillion t of CO2 — of which 13.4 trillion t is undiscovered and just 253mn t is currently considered economically viable. Almost all planned facilities intend to store CO2 in sedimentary rock formations. Most operational storage facilities are being used for enhanced oil recovery, which ultimately results in net-positive CO2 emissions, the study said.
Fully using this estimated geologic storage potential would cap the global temperature reduction to only 0.7°C.
Carbon capture and storage (CCS) is an industry that has attracted billions of dollars in investment globally over the past few years as a number of countries are increasingly viewing this as a solution to reduce emissions from the combustion of fossil fuels and from hard-to-abate industrial sectors, and to store the CO2 that is removed from the atmosphere.
There was just over 50mn t of CO2 capture and storage capacity as of the first quarter of this year, and this is set to reach around 670mn t of CO2 by 2030, according to IEA data.
Sites under consideration for CO2 storage are mostly depleted hydrocarbon fields or deep saline aquifers within geologically stable sedimentary basins.
There are multiple risks involved in the large-scale utilisation of CO2 storage that have not been well captured in emissions reduction models, the study said. CO2 leakage can occur because of seismic activity, and for storage sites located near population centres, stored carbon could potentially seep into local aquifers, posing health concerns. The rise in pressure during CO2 injections could also trigger low-intensity earthquakes.
Risks such as these, along with other considerations like the geopolitics of cross-border sedimentary basin boundaries and potential project failures, severely limit the available CO2 storage capacity that should be taken into account when planning national energy policies, the study said.
Implications on climate policy
The findings of the study have significant implications on countries' climate strategies that depend on carbon storage, as it highlights the importance of treating CO2 storage as a scarce resource and taking into account the consequences of continued emissions from fossil fuel use.
The study also points out the unequal impact on countries' storage reserves in terms of mitigation capabilities, as well as historic responsibility for emissions. More economically developed countries with high historic emissions like the US and Russia are better placed to implement geological storage solutions, while developing nations with high storage potential such as Indonesia and Brazil have contributed little to global emissions and "thus may have weak domestic incentive to exploit their storage resources unless the removals can be traded", the study said. But with trading comes large-scale transfers of captured CO2, which entails higher risks for leakage during transmissions, either through shipping or pipelines.
Some of the risks in the utilisation of CCS may be mitigated by sustainably deploying alternative approaches such as conserving and expanding land and coastal carbon sinks, and enhancing the carbon content of soils, the study said. Other carbon sequestration avenues such as mineralisation in basalt formations may also expand the CO2 storage limit, but this is still in early stages of development.
