(57b) Carbon Capture and Storage (CCS): The Way Forward

Carbon capture and storage (CCS) is expected to play an important role in meeting climate change mitigation targets (IPCC, 2018), providing a least cost pathway to decarbonise different sectors. There are a variety of potential applications for CCS, these include delivering low carbon heat, power and fuels, decarbonising industry and net removal of atmospheric CO₂ (i.e., negative emissions). This paper presents the current state-of-the-art technologies for CO₂ capture, transport, utilisation and storage from a multi-scale perspective, starting from the global level and moving to the molecular scale (based on work in Bui et al. (2018)). We provide insight on how to move the discipline forward, highlighting key research challenges that should be addressed over the course of the next decade, giving a balanced perspective on the scientific, policy and commercial priorities.

Role of CCS and negative emissions technologies

There is a broad consensus that CCS has reached the technical maturity required for specific application (i.e., power sector and industry). There are presently 23 commercial-scale CCS facilities worldwide in operation or under construction, which permanently sequester up to 37 million tonnes of CO₂ per annum (Global CCS Institute, 2019). However, IPCC integrated assessment modelling (IAM) shows that scenarios limiting global warming to 2°C requires CO₂ removal rates of 10 Gt_CO2/yr by 2050 and 25 Gt_CO2/yr by 2100. When considering a 1.5°C limit, there are no feasible scenarios without negative emissions. It is clear current CCS deployment rates do not reflect projected level required to meet emission reduction targets. In many scenarios, the dominant negative emissions technology (NET) is bioenergy with CCS (BECCS), which is likely due to the lack of other NET options within IAMs. Thus, incorporating alternative NETs into IAMs is a key research priority (Bui et al., 2018).

BECCS is currently deployed for industrial applications in 5 plants worldwide. The estimated technical potential of BECCS is a CO₂ removal rate of between 3–20 Gt_CO2/year. The resources (e.g., land, water) required to deliver BECCS is case-specific, key factors include feedstock type, region specific constraints and decisions made along the biomass supply chain. Direct capture of CO₂ from air (DAC) is technically possible, with two demonstration plants currently operating in Switzerland (Climeworks) and Canada (Carbon Engineering). There are technical and economic challenges associated with the very dilute CO₂ concentration of air, i.e., high energy requirements, significantly higher capture costs. Therefore, there is a need to address policy questions around regulating and incentivising negative emissions. Furthermore, in the absence of a mature CCS industry, attempting large-scale deployment of BECCS or DACS will be challenging.

CCS technology improvements

For the CCS technology development to accelerate, technology benchmarks need to be updated, preferably with current industrial best practice. Comparing new sorbent materials against obsolete benchmarks (e.g., 30 wt% MEA) is potentially limiting progress. Importantly, experimental testing should study these materials under conditions representative of the “real world”, e.g., high CO₂ partial pressure for desorption, presence of contaminants. With an immense number of potential materials for CCS, pilot-scale testing of all of them is not practicable. A more efficient approach to screen materials is the use of high throughput modelling and simulation approaches, which combine molecular- and process- scale information. Future designs of next-generation CO₂ capture sorbents (e.g., ionic liquids, MOFs) need to consider the cost aspects in combination with reduced energy requirements and higher capacity.

The metrics used to assess CCS technology improvement can vary. The CCS community tends to focus on reducing the cost to capture CO₂. On the other hand, the owners of the CO₂-emitting facilities prioritise minimising the cost of their low carbon product, e.g., electricity. It is important to recognise that the majority of “CCS costs” are associated with increases in capital cost, as opposed to operating cost. Whilst continued focus on improving thermodynamics is helpful, priority must be given to research which promises reduction in capital costs. Rather than just minimising the cost of capturing CO₂, R&D initiatives aimed towards “improving” CCS should take a whole systems approach. Thus, shifting the focus towards reducing the cost per unit of decarbonised product (e.g., steel, cement, power) and how the decarbonised process will compete in the market (i.e., what will be displaced by what). As the energy system becomes more diverse, not all energy technologies provide the same services. Therefore, metrics such as the “system value” is a more holistic approach to evaluate and compare low-carbon energy technologies (as illustrated in Figure 1). Distinct from intermittent renewables, coal/gas/biomass-CCS offers reliable dispatchable power, thereby providing energy system resilience and flexible operability.

CCS commercialisation and political considerations

Large-scale deployment CCS is needed for deep decarbonisation. The technical elements of CCS are well-understood. The financial and commercial models to enable CCS deployment are becoming increasingly clear. There is substantial evidence of the economy-wide GDP and employment benefits associated with CCS deployment. However, public acceptability and understanding of the impact on the political economy are at an early stage. Some governments provide generous subsidies to low-carbon technologies such as offshore wind and nuclear power, these are similar in scale as what would be required for CCS. Unlike nuclear power or onshore wind, there are no strong opponents, but neither are there advocates willing to lobby strongly for CCS. Thus, shifts in incentives and regulations are needed to enable changing of interests and economics, which will eventually lead to large-scale deployment of CCS.

References

Bui, M., Adjiman, C. S., Bardow, A., Anthony, E. J., Boston, A., Brown, S., Fennell, P. S., Fuss, S., Galindo, A., Hackett, L. A., Hallett, J. P., Herzog, H. J., Jackson, G., Kemper, J., Krevor, S., Maitland, G. C., Matuszewski, M., Metcalfe, I. S., Petit, C., Puxty, G., Reimer, J., Reiner, D. M., Rubin, E. S., Scott, S. A., Shah, N., Smit, B., Trusler, J. P. M., Webley, P., Wilcox, J. & Mac Dowell, N. (2018). Carbon capture and storage (CCS): the way forward. Energy & Environmental Science, 11 (5), 1062-1176.

Global CCS Institute (2019). CCS Facilities Database. https://www.globalccsinstitute.com/resources/ccs-database-public/ [accessed 4/2/2019].

IPCC (2018). Global warming of 1.5°C. Switzerland: Intergovernmental Panel on Climate Change (IPCC), https://www.ipcc.ch/sr15/.