GNS scientist Brad Field on the promise of carbon capture and storage

Stuart Haszeldine’s article in Science this week identifies the main issues regarding the implementation of capture and underground storage of carbon dioxide: the technology exists, but how readily can it be up-scaled, and will there be enough economic and political push to deploy it extensively by 2020?

The CCS market is an artificial one, where incentives are more political than economic. However, if permission to establish sites that create large volumes of CO2 is made dependent on successful CCS, the economic equation shifts dramatically. A key factor that will probably become more cogent is public perceptions of climate change effects. If, or when, people come to believe climate change effects are as profound and severe as predicted by scientists then emitters of CO2 might find their reputations and customer base are harmed. What will cause such a shift in public perception, when will it occur, and which industries will be tarred?

Dr Haszeldine points out that public acceptance of CCS will be a crucial element in the speed of its implementation. Which fear will win out: leakage from geological storage sites (unlikely to be significant), short term power blackouts, or long term climate change?

In terms of emissions, there is nothing wrong with burning fossil fuels per se, as long as there is full CCS. Fossil fuels provide billions of dollars each year to our GDP. Countries with high per capita GDPs can afford high environmental standards and CCS. It would not be in New Zealand’s short term economic interests to immediately stop industries that produce CO2 but, at the same time, it will not be in our medium to long term interests for them to continue without CCS, because of the consequences of climate change. A 2oC rise in global temperatures should be seen as a maximum, rather than a comfortable target.

It is clear, from a broad geological perspective, that parts of New Zealand are likely to have vast volumes of rock capable of storing CO2, and that storage volume, in theory, should not be an issue. Pipelines can carry CO2 for hundreds of kilometres, but distance adds cost.

What CO2 does New Zealand have, ready for storage? Currently, our only point source of pure CO2 available for storage is from Vector’s plant in Taranaki, where CO2 is stripped from Kapuni natural gas. It would make sense to develop an underground storage site in Taranaki, near to potential new gas discoveries and where petroleum infrastructure is already present, or near major coal reserves such as the Southland lignites. As Dr Haszeldine notes, pipelines from point sources of CO2 can join at hubs near underground storage facilities. It might suit New Zealand to have one or two large storage sites fed by distributed, comparatively small point source emitters. Retro-fitting plants such as Huntly to capture CO2 is likely to be expensive and might be economically practical to implement only as part of plant replacements; we can probably expect most of our main point source emitters to continue to emit for some time, beyond the 2020 deadline recommended by Dr Haszeldine.

Dr Haszeldine points out that a significant issue for underground CO2 injection is the consequent build-up in pressure. He notes two features associated with this: that a depleted oil or gas field can be re-pressured to its original state, and that injecting CO2 can require pressure-relief wells to be drilled, to remove natural fluids from adjacent areas. The first assumes the reservoir and seal rocks retain their properties during pressure reduction during extraction of hydrocarbons and this does not always strictly hold, but it does provide a basis for initial assessments of capacity. The depleted Maui gas field could, for example, store all New Zealand’s current CO2 point source emissions for many years to come. The second – drilling pressure relief wells would probably provide saline water that, if treated, could be suitable for agricultural use.

Dr Haszeldine’s article discusses only storage of CO2 in underground pore space. Storage can also occur through injection into coal seams, but this might prevent future use of the coal and would store only comparatively small volumes of CO2. An interesting question for New Zealand is whether locking CO2 away permanently in minerals would be viable. Reacting CO2 with minerals to form new, stable minerals is energy-intensive and perhaps not economically competitive with large-scale underground storage. However, if New Zealand has good supplies of suitable minerals, and readily available “green” energy (e.g., wind, geothermal or solar), then this approach might be an economical option for our small emitters that might be isolated from future underground storage sites. Also of note is the possibility of New Zealand having “negative emissions” through CCS, if CO2 emissions from biofuel use were to be captured and stored.

New Zealand has been fortunate in having a close association with the Australian-based CO2CRC (Cooperative Research Centre for Greenhouse Gas Technologies) and the International Energy Association (IEA) for several years. This has enabled New Zealand to tap into international research findings and methods, and an initial review of underground storage options in New Zealand has just been completed. This has been supplemented by a government- and industry-funded programme through the Foundation for Research, Science and Technology. Government policies relating to CCS are currently being developed.

Dr Haszeldine is correct in saying CCS can be pivotal in reducing global greenhouse emissions. CCS can and should be implemented in New Zealand. This will probably be more in relation to new power station builds, processing gas from new giant gas discoveries and the use of other fossil fuel resources such as the Southland lignites. His article identifies some key points why CCS, and most particularly the capture side of CCS, has not yet been widely applied on a large scale. Some of Dr Haszeldine’s key questions are highly relevant to us: where, at what scale, how soon and how will it be funded? Two degrees of warming is too high a risk to take. We should act now to curb emissions, while still meeting our growing energy needs and safeguarding our economy – CCS can help to do both.

Brad Field, GNS Science, Lower Hutt