Sustainability & CSR
The advantages and challenges of CCUS
Carbon Capture Utilisation and Storage will play a role in decarbonisation but realising implementation at scale will require significant cost reductions or technological breakthroughs.
By Bart Linssen
When we burn fossil fuels, we take carbon out of the ground that has gradually been stored there over millions of years. By doing that we risk recreating the extreme climate of millions of years ago rendering earth less suitable for humans and other species. Why not put carbon back into the ground?
Carbon Capture Utilisation and Storage (CCUS) is a technology designed to reduce carbon dioxide (CO₂) emissions from industrial processes and power generation. It involves capturing CO₂ and either using it or storing it underground.
1. Capturing CO₂
The first step in the CCUS process involves capturing CO₂ emissions produced during industrial activities or fossil fuel combustion. There are several methods for capturing CO₂:
Post-combustion capture captures CO₂ after fossil fuels have been burned. Flue gas passes through a chemical solvent, such as an amine, which binds to the CO₂. The solvent is then heated to release the CO₂ for further processing.
Pre-combustion capture: In this approach, fossil fuels are gassified before combustion, allowing CO₂ to be removed from the fuel source itself. This method is still being developed for power plants but is used in some industrial applications.
Oxy-fuel combustion: Fuel is burned in an environment with nearly pure oxygen, resulting in a more concentrated stream of CO₂ that is easier to capture.
Direct Air Capture: CO₂ is removed directly from the atmosphere using chemical reactions.
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Advantages and challenges of CCUS methods |
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Technology |
Description |
Advantages |
Challenges |
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Post-combustion |
Captures CO₂ from flue gases using chemical solvents after combustion. |
Can be retrofitted to existing power plants. Widely researched and tested. |
Energy-intensive. Requires solvent regeneration and disposal. Lower CO₂ concentration. |
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Pre-combustion |
Separates CO₂ from synthetic gas produced by gassifying fuels before combustion. |
Higher efficiency in capturing CO₂. Produces hydrogen as a clean fuel. |
Complex process. Expensive. infrastructure limited to new plants or major retrofits. |
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Oxy-fuel combustion |
Burns fuel with oxygen instead of air, producing a concentrated CO₂ stream. |
Produces a high-purity CO₂ stream. Reduces nitrogen oxides (NOx) emissions. |
High cost of oxygen production. Requires significant changes to existing combustion systems. |
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Direct Air Capture (DAC) |
Removes CO₂ directly from the atmosphere using chemical reactions. |
Can be deployed anywhere. Potential for negative emissions. |
Highly energy intensive. Current technology is expensive. Needs significant scale-up. |
2. Transporting CO₂
Once captured, the CO₂ is compressed and transported to a storage site. This can be done via pipelines, ships, or other transport methods. The compression process reduces the volume of CO₂, making it more efficient to move.
3. Storage
3a. CO₂ storage
The final step involves injecting the captured CO₂ into geological formations deep underground for permanent storage. Common storage sites include:
- Depleted oil and gas reservoirs: These formations can securely hold CO₂ while potentially enhancing oil recovery through techniques that inject CO₂ into existing reservoirs.
- Saline aquifers: These are porous rock formations filled with salty water that can also store significant amounts of CO₂.
- Basalt formations: In some cases, CO₂ can be dissolved in water and injected into basaltic rock formations, where it mineralizes over time.
Saline aquifers are made of a porous and permeable rock which is saturated with water. The top layers are commonly used for drinking. However, deeper underground, the aquifer salt content makes it non-potable. Of all the potential reservoirs that are considered for carbon storage, deep saline aquifers provide the greatest potential storage capacity.
A layer of impermeable rock traps the carbon dioxide inside the aquifer. The CO₂ is injected into the aquifer by a prepared pipeline which has breached the rock layer. The CO₂ is injected in a supercritical state (both gaseous and liquid), which is lighter than water. Once injected the supercritical CO₂ floats up to the impermeable rock layer. It then slowly dissolves into the saline water and is sequestered within the aquifer.
3b. CO₂ utilisation
Carbon Capture and Utilisation (CCU) is being adopted across various industries, offering innovative solutions for reducing carbon emissions while creating valuable products. Key sectors currently utilising CCU include the chemical manufacturing industry, where captured CO₂ is converted into chemicals such as methanol and urea, and the construction industry, which uses CO₂ in the production of carbonated concrete and other building materials. The energy sector, particularly in the production of sustainable fuels, is also a significant area for CCU applications, with technologies that convert CO₂ into synthetic fuels for transportation, including sustainable aviation fuels (SAF) and fuels for maritime and trucking industries.
4. CCS and CCU in Taiwan
4a. Storage
In Taiwan, there is potential for storing CO₂ in saline aquifers deep underground below an impermeable barrier rock layer (the caprock) where it is permanently stored.
The Taishi Basin is located offshore to the west of Taiwan, specifically north of the Miaoli and Hsinchu regions. It is part of a series of sedimentary basins in the Western Offshore Taiwan (WOT) area. This basin is characterised by a relatively low fault activity and stable tectonic background, making it a candidate for geological carbon storage (GCS) initiatives.
The total available capacity in the Taishi basin for CO₂ storage in Taiwan is estimated at 46 billion tons, with 13.8 billion tons in onshore plains, 16.8 billion tons within 0-25 km from the coastline, and 15.3 billion tons within 25-50 km from the coastline. Considering cost and human activities, carbon storage wells in the sea area within 25 km from the western coastline of Taiwan are the most likely candidates for storage. Each well can store one million tons of CO₂ per year. Under Taiwan’s net zero 2050 plans, in total, Taiwan needs to store 40 million tons of CO₂ annually.
4b. Developments
Taiwan is actively developing several carbon capture and sequestration (CCS) demonstration projects as part of its commitment to achieving net zero emissions by 2050. Here are some key projects:
- Taiwan Power Company (Taipower) - Taichung Power Plant: Taipower is planning a carbon storage demonstration site at the Taichung Power Plant, which is expected to conduct trial injections of CO₂ in 2025. This project aims to verify the feasibility and safety of domestic geological storage technology.
- CPC Corporation - Miaoli Tiezhenshan: CPC is also involved in carbon sequestration tests at its site in Miaoli, contributing to the overall goal of capturing and storing approximately one million tons of CO₂ annually from various sources.
- Taiwan Cement Corporation: Taiwan Cement Corporation has established a pilot plant for calcium looping carbon capture technology, capable of capturing one ton of CO₂ per hour. Plans include scaling up to capture 100,000 tons of CO₂ per year by 2030. Calcium looping is a second-generation technology utilising a two-step process involving calcium carbonate (CaCO3) and calcium oxide (CaO) to capture and release CO₂.
- China Steel Corporation: China Steel has set up a demonstration plant that captures 100 kg of CO₂ per day using chemical absorption methods. This facility serves as a testing ground for various capture technologies.
5. Cost of CCS
The cost of CCS remains a significant barrier to widespread adoption. Firstly, when equipping an existing power plant with carbon capture equipment, the efficiency of the power plant is reduced by approximately 30%. In addition to the costs associated with the loss of efficiency, there are the direct costs of carbon capture. The International Energy Agency estimates these direct costs for CO₂ capture are NT$1,900-4,000 per ton of CO₂ for power generation applications. These costs per ton for carbon capture would translate into an estimated NT$3-5 per kWh addition to the cost of fossil fuel electricity generation.
Looking ahead, expectations for CCS costs are mixed. While some projections suggest that costs could decline significantly with increased deployment and technological advancements, however the pace of this reduction has historically been slow compared to other energy technologies.
Direct Air Capture (CO₂ capture directly from the ambient air), a technology frequently reported in the media, is even more expensive and costs an estimated NT$4,000-11,000 per ton of CO₂ and would of course need to be powered by a renewable energy source in order to be an effective carbon reduction technology.
Where CCUS is most likely to be deployed
Due to the high costs, the main use of CCUS is likely to be in hard to abate CO₂ emissions, those that are particularly challenging to reduce due to technological, economic, and physical constraints. These emissions primarily arise from sectors where current abatement technologies are either prohibitively expensive or not yet mature enough for widespread implementation, especially those listed below.
Heavy industry
Cement production: Cement manufacturing is energy-intensive and produces significant CO₂ as part of its chemical processes, making complete decarbonisation challenging.
Steel production: Like cement, steel production is reliant on fossil fuels and involves high-temperature processes that are difficult to electrify.
Chemicals: The chemical industry also faces hurdles due to the need for high energy inputs and complex production processes.
Transport
Aviation: Long-distance flights currently depend on high-carbon fossil fuels, with no viable alternatives available at scale.
Shipping and heavy-duty transport: These modes of transport require energy-dense fuels, which complicates the transition to cleaner alternatives like electric or hydrogen-powered vehicles.
Waste incineration
Waste generation: Taiwan’s waste management strategy emphasizes incineration to reduce landfill use and recover energy. Although no data is available, we can estimate emissions from waste incineration at 60 million tons partly hard to abate CO₂, equivalent to 20% of Taiwan’s reported CO₂ emissions.
Conclusion
Taiwan has significant potential for CCUS, particularly for storing CO₂ in saline aquifers, with the Taishi Basin being a promising site. Storage capacity is an estimated 46 billion tons of CO₂. Taiwan is actively developing several carbon capture and sequestration projects, including a demonstration site at the Taichung Power Plant and at the CPC Corporation site in Miaoli. However, the high cost of CCUS presents a significant barrier to widespread implementation; for example, adding carbon capture equipment to power plants reduces efficiency by approximately 30% and in addition the direct costs of CO₂ capture are estimated at NT$1,900-4,000 per ton CO2 for power generation. Direct air capture is even more expensive, at NT$4,000-11,000 per ton CO2. As a result, CCUS is most likely to be deployed only in hard-to-abate sectors in Taiwan, such as heavy industry, air transport, shipping, and waste incineration. Therefore, while CCUS is essential for reducing carbon emissions in Taiwan and meeting its 2050 net zero goal, its widespread implementation depends on cost reductions and technological advancements.
Bart Linssen is the Director of Renewable Energy at RCI Engineering
