CO2 utilization could prove to be a fateful sidetrack in the climate mitigation debate

In 2014 the concentration of CO2 in the atmosphere surpassed 410 ppm [1]. Increasing concentration of greenhouse gases in the atmosphere increases the global mean surface temperature, which is widely accepted to be the main reason for human induced climate change. The Paris Agreement aims at cutting CO2 emissions to reach the target of maximum temperature increase of 2°C. Carbon Capture and Storage (CCS) is one technology able to limit emissions of anthropogenic CO2 to the atmosphere.

Capturing and storing CO2 underground

Carbon Capture and Storage (CCS) refers to capture and permanent underground storage of CO2. The purpose of CCS is to avoid CO2 emissions to the atmosphere. Large point sources such as industrial emissions are most suitable for CCS. Post-combustion capture based on amine solvents, also called gas sweetening, is currently the most mature technology for CO2 capture from large point sources. In the post-combustion capture concept, CO2 is separated from other flue gases, purified, and compressed to liquid CO2 before being transported to a permanent storage.

CCS is a costly affair

One of the first industrially operational CCS facilities for coal-fired power plants, the SaskPower Boundary Dam CCS project in Saskatchewan, has seen costs surpassing USD 1.5 billion – and counting. Cost estimates for the Norwegian full-chain CCS project (capturing CO2 from a cement plant and from a waste incineration plant and storing it in formations below the North Sea) reach roughly EUR 0.8 – 1.3 billion for planning and investment, with an additional EUR 37 – 94 million in operating costs per year [2].

Capturing and utilization of CO2 could stimulate the market

CCS business cases are few in the current CO2 market. This, coupled with the increasing pressure to decrease CO2 emissions has made industry look to an alternative; Carbon Capture and Utilization (CCU). CCU refers to the use of CO2 as feedstock to produce fuels, chemicals and materials. The demand for CO2 as feedstock in industrial processes could possibly create another source of income for CO2 emitters, either by selling waste CO2 as raw material or producing and selling products from waste CO2.

The capture part of the CCS and CCU processes is the same, but this is where CCS and CCU start to go separate ways. While carbon in CCS systems is permanently deposited underground, carbon in CCU systems is used in the production of new products. The use of these new products will eventually emit the CO2 to the atmosphere.

Abanades et al. [3] compared the climate change mitigation potential and associated costs of CCS vs. CCU and concluded with the mitigation costs for a CCU system to be significantly higher than for a CCS system producing the same fuel. The difference between CCS and CCU systems are illustrated in Figure 1.

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Figure 1. CCS (left) vs. CCU (right).

CCU has very limited potential as a climate change mitigation strategy

The potential of CCU as a climate mitigation tool lies primarily in the ability to replace fossil fuels in the production of a secondary CCU product. However, this only has a limited effect on net CO2 emissions to the atmosphere. Another major challenge when using waste CO2 as feedstock for other processes is the amount of energy needed to convert the zero-energy CO2 into a product.

Consequently, the effectiveness of the CCU system as a climate mitigation tool is strongly dependent on how the CO2 conversion is powered. For instance, converting CO2 into methanol for transportation fuel requires approximately 1.8 MW electricity for each MW of methanol produced. This electricity must originate from a low-carbon source, for instance wind power, solar power or sustainable bio-power. The source of the carbon also affects the role of CCU as a climate mitigation tool. Using waste CO2 originating from fossil carbon will have a lower effect than using CO2 from an atmospheric source (biomass or direct air capture).

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We need to stop talking and start acting

According to the Mercator Research Institute [4] the carbon budget for limiting the global temperature increase to 1.5°C was surpassed on September 9 this year. Similarly, we have 17 years left before the carbon budget for 2°C runs out. 17 years is not a long time when it comes to shifting industrial practices.

In a decarbonized society, CCU could play an important role by recirculating carbon already present in the carbon cycle. However, the urgency of reducing emissions combined with the relatively low potential of CCU for CO2 reductions further adds to the challenges of CCU as a climate mitigation tool. In the worst case, CCU could be a fateful sidetrack in the climate mitigation debate.

What we need to do now is to take a step further from the analyses and the debate, and start acting. More ambitious national climate targets, both for ETS and non-ETS sectors, long-term goals and industrial CO2 emission management tools can facilitate the investment environment in favor of CO2 reduction.

With no real alternatives to store CO2, Finland should be proactive and take advantage of the Norwegian full-scale CCS initiative. By demonstrating and facilitating CO2 capture from Finnish industries with subsequent storage in the North Sea, Finland could be among the first great movers in industrial CCS clusters across national borders.

Take-aways

  • CCS and CCU address the issue of climate change mitigation in fundamentally different ways. While CCS offers a permanent removal of CO2, the majority of CCU systems will only have a limited effect on climate change.
  • For the CCU system to have an effect on CO2 emissions to the atmosphere the energy used for CO2 conversion must be low-carbon and/or CO2 must come from an atmospheric source.
  • The implementation of CCS is urgent, and a significant large-scale effort is needed to handle the continuously increasing CO2 emissions.
  • We must act now and acting is dependent on political support. We need to demonstrate large-scale CCS in different industrial clusters, and prove that full-chain CCS on an international level is possible.

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Kristin Onarheim
Research Scientist, expert in techno-economic assessment and feasibility studies of CCS and CCU concepts at VTT
kristin.onarheim(a)vtt.fi

 

References:

[1] Scripps Keeling curve

[2] https://www.gassnova.no/en/Documents/Feasibilitystudy_fullscale_CCS_Norway_2016.pdf

[3] Abanades, J.C.; Rubin, E.S.; Mazzotti, M. and Herzog, H.J. 2017. On the climate change mitigation potential of CO2 conversion to fuels. Energy & Environmental Science, 10, 2491.

[4] https://www.mcc-berlin.net/en/research/co2-budget.html

 

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