A range of carbon dioxide capture technologies have been developed, including amine-based routes and calcium looping methods, some of which are now considered to be at technology readiness level (TRL) 9. These technologies have been deployed across the world in large-scale carbon capture, utilisation and storage (CCUS) projects, permanently storing the CO2 in geological formations, which in 2020 had a capture and storage capacity of 40 MtCO2 per year. Direct air capture (DAC) technologies, capable of capturing CO2 directly from the atmosphere, have recently been developed and demonstrated.
As well as storing the CO2 in geological formations, there is increasing interest in the chemical transformation of captured CO2 to value-added products, such as building materials, chemicals, polymers, and synthetic fuels. This is driven partly by goals to increase sustainability, lower emissions, and the move towards more circular production routes. Developments have also been driven by realisations that producing some products using CO2 as a feedstock could lead to improvements in the product or the process, such as enhanced properties or lower feedstock costs. CO2 is already used extensively for urea manufacture in the fertiliser industry, for enhanced oil recovery (EOR), and for food and beverage production, with other conventional applications including use in fire-extinguishers, greenhouses, and cooling systems. Carbon capture and utilisation (CCU) refers to CO2 utilisation in which the supplied CO2 is captured either from an emission point source (e.g. fossil fuel combustion in an industrial plant) or directly from the atmosphere (DAC). With large volumes of CO2 projected to be captured in the longer term, CCU and CCS can play complementary roles in climate change mitigation.
For many utilisation routes, CO2 sequestration is only temporary with utilised CO2 being emitted to the atmosphere as the product is combusted or degrades at its end-of-life. Fuel products may last for less than a year, chemicals less than 10 years, and polymers less than 100 years. At the end of the product's life, the carbon atoms contained within these products often enter the atmosphere as CO2, with exceptions where this carbon is captured and stored permanently, e.g. in building materials. In absolute terms, these re-emitting CCU routes are therefore carbon neutral at best but typically net-positive in emissions when their entire life cycle is considered.
- Almost all CCU routes showed potential for lower life cycle emissions per tonne of product compared to their counterfactual. The potential scale for deployment was much greater for fuels and building materials than for chemicals and polymers, which typically had existing markets orders of magnitude smaller.
- For fuels, annual abatement levels greater than 1 GtCO2-eq could be achieved for direct replacement 'drop-in' fuels. For building materials, annual abatement levels greater than 100 MtCO2-eq could be achieved. CCU building materials also have potential to offer negative emissions when CO2 is sourced from DAC. With the exception of methanol, the total mitigation potential of polymers and chemicals was limited to below 20 MtCO2-eq per year.
- Most CCU routes within the chemicals and fuels categories were found to be considerably more expensive than conventional fossil-based production routes, due to high energy requirements for green hydrogen feedstock, low yields and high catalyst costs. CCU building materials and polymers can offer cost reductions.
- There are a range of potential co-benefits (e.g. re-use of waste residues, raw materials reduction, safer production process, improved product properties, energy storage) for CCU routes but there can also be trade-offs (e.g. high energy demand, additional land-use, increased water consumption).
- Deployment of CCU routes may be more favourable in regions with: (i) low-cost or extensive availability of renewable energy; (ii) high cost or lack of available fossil resources; or (iii) significant low-carbon ambition coupled with political or regulatory mechanisms. The current distribution of CCU R&D projects is concentrated mostly in the EU and the US.
- CO2 utilisation opportunities are diverse, and each route has its own specific drivers, barriers, and enablers. There are, however, some common themes that span across, e.g.: regulations such as mandates or standards, financial provisions, policies that level the field by recognising sustainability benefits, sustainable product development, regional energy availability, costs.
- Report sufficient data to allow for life cycle and techno-economic assessments (LCA and TEA).
- Highlight priority areas for CCU development and identify end-uses where CCU is expected to be a necessary component of future decarbonisation pathways.
- Engage with the public and policy makers to improve understanding of the benefits and limitations of CCU routes.
- Increase awareness of upstream emissions in supply chains and identify opportunities to switch to more sustainable production routes.
- Introducing support mechanisms that allow CCU to receive recognition for sustainability benefits.
- Incorporate CCU products appropriately into existing support schemes, regulations, and product standards.
- Provide funding for research programmes, demonstration projects etc.
- Develop and clarify frameworks for the carbon accounting of CCU routes.