Similar to how plant life functions, there are two routes for captured CO₂
1. Utilisation by converting into products (CCU)
2. Permanent storage (CCS)
Utilisation of Captured Carbon
Once carbon dioxide is captured they can be utilised on-site or transported for various other applications. This captured carbon can be used directly (without chemical alteration) or indirectly (post transformation). CO₂ is primarily used in the fertiliser industry and for enhanced oil recovery. Once transformed, CO₂ can be used to produce synthetic hydrocarbon fuels, CO₂-based chemicals and polymers, building materials and speciality carbonates. Utilisation has the added benefit of generating revenue to offset the cost of capture and transport.
Companies utilising CO₂
North America
Twelve, US - PANGAIA (CO₂ made sunglasses), e-Jet (carbon-neutral fuels). More here.
Skyonic, US - CO₂ capture at Capitol Aggregates cement plant to produce sodium bicarbonate, bleach and hydrochloric acid
CarbonCure, CarbonBuilt and Solidia Technologies - Development and commercialisation of carbonated concrete production through CO₂-curing
50kt/year barium carbonates demonstrator commissioned by China National Building Material in 2016
b. 2.3kt precipitated calcium carbonate plant commissioned by Guodian Electric Power Datong company in 2022
Europe
Carbon8 Systems - Integrated CO₂ capture and recarbonation technology of waste residues (‘’CO₂ ntainer’’) at Vicat cement plant in France in 2020
Storage of Captured Carbon and Monitoring
Once the CO₂ reaches the storage location, it can be injected deep underground into a suitable geological formation for permanent storage, such as saline aquifers (e.g. sandstones that are filled with brine), depleted oil or gas fields, and potentially in other types of rocks such as deep coal seams or basalts.
Oil and gas reservoirs present an opportunity for both geologic carbon dioxide storage and enhanced oil recovery. By injecting CO₂, additional oil can be extracted from developed sites, offering economic benefits. These reservoirs are considered promising for CO₂ storage due to their long-standing containment of fossil fuels and the availability of valuable data from past exploration, ensuring secure long-term storage.
Deep or thin coal beds, which may not be economically viable for mining, could also offer potential for CO₂ storage and enhanced resource recovery through methods like enhanced coal bed methane recovery (ECBM).
The safest method of storage is storing it reactive rock formations. Vast quantities of carbon are naturally stored in rocks. By imitating and accelerating the natural process of mineral formation it is possible to provide a safe carbon sink. Carbonated water (CO₂ dissolved in water) is injected into into the favourable rock formations preferably basalt, where the solution reacts forming stable carbonates via natural process of rock formation at a highly accelerated rate. These rocks will remain undisturbed for thousands of years making it a permanent carbon sink.
Source: Carbfix
The active rift zone in Iceland alone is estimated to store over 400 Gt of CO₂. The theoretical storage capacity of the ocean ridges is significantly larger than the estimated 18,500 Gt CO₂ stemming from the burning of all fossil fuel carbon on Earth making this a viable option for storage.
Monitoring, mitigation and verification (MMV) of CO₂ in the subsurface is critical and is mandated through regulations and legislation. Once the CO₂ is injected, it is essential to confirm that it is safely and permanently stored. This can be monitored using down-hole sensors, time-lapse seismic, fluid and soil gas analysis, and aerial/satellite imaging. Australia is currently working on
the oil reservoir that are water-dominated, and contain residual oil saturation tend to be unsuitable for economic production.
Limitations of Carbon Capture
1. High Costs
The technology can be prohibitively expensive requiring significant investments in R&D and infrastructure. If no subsidies are provided, the cost of production will increase to retrofit existing facilities with CCUS technology along with a 50% to 80% increase in the cost of electricity to pay for its implementation. There are currently no regulatory drivers in most places to incentivise or require the use of CCS. Many critics have questioned the cost efficiency of basalt formation storage. For this option, 25 tons of water will be required for each ton of carbon dioxide to be buried. There is a possibility that volcanic rock microbes can also digest the carbonates and hence produce methane gas which can be another problem.
2. Energy Intensive
Capturing carbon is energy intensive. Once captured, more energy is spent to transport it to storage facilities. In the process of Direct Air Capture, 2 MWh of energy to capture one tonne of CO₂. To capture a year’s worth of global CO₂ emissions, we would require 120,000 TWh of energy which is close to the amount of energy the world uses per year.
3. Prolonging the Energy Transition
Since carbon capture technologies facilitate lower emissions, governments tend to become complacent with the existing infrastructure retrofitted with CCUS and removes incentive to transition to renewable sources at an accelerated pace. To achieve net zero, the focus should be more on a transition to clean energy as reducing emissions alone is not sufficient.
4. Defeating the purpose
Emissions from power generation using fossil fuels account to ¼ of the total GHG emission and about 60% come from agriculture, transportation etc. A majority of the emissions are from the activities directly related to CCUS. Using captured CO₂ to enhance oil refinery is counter-active since the mined oil when burned emits more CO₂ into the atmosphere. Hence captured CO₂ needs to account for all emissions including future emissions to help us get closer to Net Zero.
5. Environmental Risks and public perception
The possibility of leakages when transporting CO₂ or at the storage facilities exists since a large volume is concentrated in a small location. This is a significant threat to the immediate environment and to the people working in the vicinity. According to the Intergovernmental Panel on Climate Change, if CO2 were to leak from a pipeline, a concentration between 7% and 10% in the ambient air could pose an immediate threat to human life. The awareness of public when it comes to CCS is low according to a study by St. Petersburg Mining University in Russia. NIMBY (Not-In-My-BackYard) movements often interfere with CCS projects as people perceive this as as threat to their lifestyle and health
Road to capturing more carbon capture
According to McKinsey analysis, CCUS uptake needs to grow 120 times by 2050 for countries to achieve their net-zero commitments3, reaching at least 4.2 gigatons per annum (GTPA) of CO₂ captured, with some estimates ranging from 6.0 to 10.0 GTPA.
Government Regulations
- The United States government passed the Inflation Reduction Act of 2022 increasing carbon capture tax credits by 70%. This subsidy provides $85 per ton for sequestered industrial or power emissions, and $180 per ton for emissions captured directly from the atmosphere and sequestered.
- As part of Budget 2021, the Canadian government is accepting grant proposals to invested $319 million over seven years into R&D, and demonstrations to advance the commercial viability of CCUS technologies.
- In 2022, the Australian government announced an investment of over $500M to support low emissions across LNG and clean hydrogen production, and enhanced supply chain.
- The EU Innovation funds aims to allocate €25 billion towards low-carbon technologies by 2030. Similarly the UK and the Dutch governments have launched new strategies for industrialised decarbonisation and subsidies for CCUS respectively
- There are approximately 15 CCUS hubs (A CCUS hub is a cluster of emission facilities that share the same CO₂ transportation and storage or utilisation infrastructure) globally under various stages of development, with many more being planned.
Future use of captured carbon
- Fuel generation - Captured CO₂ can be reacted with hydrogen to create hydrocarbon chains that make up liquid fuels. Another way is to use microorganisms. They consume CO₂ during photosynthesis and produce sugars like glucose. Some microorganisms can ferment these sugars to produce ethanol whereas others can produce lipids, proteins and starches containing hydrocarbon components that can be refined into liquid fuel.
- Future emission sources may exist near facilities that use captured CO₂ to create products such as fuels, chemicals, and building materials, and near oil and gas wells where they can be used for enhanced oil and gas recovery (EOR/EGR)
- Beverage industry - Beverage (alcoholic and sof-drinks) companies are set to scale the re-use the CO₂ generated during production for carbonation, preventing them from escaping into the atmosphere. Finland-based start-up Aircohol takes CO₂ captured from breweries and distilleries and uses it as raw material to produce a new type of alcohol. The result is crop-free liquor with up to 50% reduced carbon footprint.
- Large scale use of captured carbon to produce CO₂ Enriched Concrete, bio-composite foamed plastics, fertilisers etc
With government regulations becoming tighter, facilitating scaling of captured CO₂ usage and innovation, we are hopeful to be on track to becoming a net zero world in 2050.
References
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[2] MIT Climate, “How much carbon dioxide would we have to remove from the air to counteract climate change?,” MIT Climate Portal, Oct. 26, 2023. https://climate.mit.edu/ask-mit/how-much-carbon-dioxide-would-we-have-remove-air-counteract-climate-change
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