Can Carbon Capture Produce Electricity?
Carbon capture and storage (CCS) is a process that captures carbon dioxide emissions from sources like coal power plants and either reuses or stores the CO2 so it will not enter the atmosphere (National Grid). The goal is to reduce the impacts of climate change by preventing large quantities of CO2 from reaching the atmosphere. One potential use of captured carbon is for electricity generation. This article examines whether carbon capture can be an effective method for producing electricity.
There are promising applications of carbon capture for generating electricity, but there are also considerable challenges and limitations that need to be addressed. On balance, the evidence suggests that while carbon capture alone cannot provide a complete solution for clean electricity production, it can play a valuable role as part of a broader strategy to produce low-carbon energy when implemented properly.
How Carbon Capture Works
Carbon capture and storage (CCS) involves separating CO2 from industrial and energy-related sources, transporting it, and securely storing it deep underground where it will not enter the atmosphere. There are three main steps in CCS: capture, transport, and storage.
The CO2 capture process separates CO2 from other gases produced in electricity generation and industrial processes by one of three main methods: post-combustion capture, pre-combustion capture, and oxyfuel combustion. Post-combustion capture, the most widely used method, uses a liquid solvent to absorb CO2 from flue gas after combustion. Pre-combustion capture converts fuel into CO2 and hydrogen before combustion, and extracts the CO2. Oxyfuel combustion uses oxygen instead of air for combustion to produce flue gas with high CO2 concentrations.
Once captured and separated, the CO2 is compressed into a liquid-like state and transported via pipeline or ship to a suitable storage site. Potential storage sites include depleted oil and gas reservoirs, deep saline formations, and deep unmineable coal seams. The CO2 is then injected deep underground for permanent storage. Careful site selection and monitoring helps ensure the CO2 remains trapped underground.
CCS technologies allow major CO2 emitting industries to reduce their emissions significantly. Capturing and storing CO2 can prevent it from entering the atmosphere when fossil fuels are used for electricity generation and industrial processes.
Using Captured Carbon Dioxide
Once carbon dioxide is captured from industrial processes, power plants, or directly from the atmosphere, there are several potential uses for the gas (1). One major use is enhanced oil recovery, where the CO2 is injected into declining oil fields to extract remaining crude oil. The injected CO2 mixes with the crude oil, decreasing its viscosity and allowing more oil to flow to production wells (2). Over 60% of captured CO2 in the United States is currently used for enhanced oil recovery (1).
Captured carbon can also be stored underground in a process known as geological sequestration. The CO2 is compressed into a dense liquid and injected deep underground into porous rock formations. The CO2 fills the pore spaces in the rock and becomes trapped, preventing it from escaping into the atmosphere. Potential underground storage sites include depleted oil and gas fields, deep saline aquifers, and deep unminable coal seams (3). While underground storage is considered safe and permanent, some concerns remain about leakage over time.
(1) https://www.c2es.org/content/carbon-capture/
(2) https://news.climate.columbia.edu/2019/05/29/co2-utilization-profits/
Generating Electricity from Carbon Capture
Once carbon dioxide has been captured, it can be used to generate electricity. One approach is to use the captured CO2 to drive turbines and generate power, similar to how natural gas is used in gas turbine power plants. This can potentially offset some of the energy penalty associated with carbon capture processes.
An emerging technology for electricity generation from captured carbon is the Allam cycle. This uses high-pressure supercritical CO2 to drive a specialized turbine. The Allam cycle has potential efficiency advantages compared to traditional steam cycles. For example, an Allam cycle demonstration plant in Texas achieved a 50% thermal efficiency, higher than typical coal power plants.[1]
However, generating electricity from captured CO2 is still in the early stages of development and faces challenges. The costs are generally higher compared to generation from natural gas or renewables. But as the technology matures, costs are expected to decline. Using captured CO2 for power generation can offset capture costs and provide environmental benefits by displacing fossil fuel use.
[1] https://netl.doe.gov/carbon-capture/power-generation
Case Studies
There are several notable examples of operational carbon capture electricity plants around the world. Two prominent case studies are the Petra Nova project in Texas and the Boundary Dam project in Canada:
The Petra Nova project, located at the W.A. Parish power plant near Houston, Texas, began operations in 2017. It is the largest post-combustion carbon capture facility in the world, capable of capturing up to 1.4 million tons of CO2 annually from a 240 MW slipstream of flue gas. The captured CO2 is then used for enhanced oil recovery in nearby oil fields. According to a case study from MIT Energy, Petra Nova demonstrated that carbon capture could be done economically at an existing coal-fired power plant. However, the project did receive over $190 million in funding from the U.S. Department of Energy.
At the Boundary Dam power station in Saskatchewan, Canada, Unit #3 was retrofitted with carbon capture capabilities and began operations in 2014. This was the world’s first application of full-scale post-combustion carbon capture technology on a coal-fired power plant. The project can capture up to 1 million tons of CO2 per year, which is then used for enhanced oil recovery. According to the International CCS Knowledge Centre, the Boundary Dam project faced numerous technical challenges during development and operation. This highlights the difficulties in scaling up first-of-a-kind carbon capture systems.
Other notable operational examples include the Searles Valley Minerals plant in California, the Shute Creek gas processing facility in Wyoming, and the Alberta Carbon Trunk Line connected to an fertilizer plant in Canada. While most current projects are focused on carbon utilization or enhanced oil recovery, these plants demonstrate that carbon capture at scale is possible today.
Challenges and Limitations
Carbon capture technology faces some key challenges and limitations that have prevented more widespread adoption and scalability so far. The two biggest challenges are the high costs involved and the energy penalties associated with carbon capture processes.
Most carbon capture methods require substantial amounts of energy input, reducing the overall efficiency and output of power plants. The energy penalty can reduce a power plant’s output by up to 30% for post-combustion capture and 15% for pre-combustion capture (Fu, 2012). This lost energy translates to higher operational costs and can make carbon capture less economically viable.
Additionally, the capital costs of building carbon capture facilities are very high. Retrofitting existing plants is expensive, with estimates ranging from $500 million to $1 billion for a 500 MW coal plant (Smit, 2014). The costs involved limit how many companies and utilities are willing to invest in and adopt carbon capture capabilities.
Finally, some carbon capture systems like DACS can have intermittency challenges. Factors like weather and air flow affect the consistency and reliability of CO2 capture, meaning the technology may not work around the clock. Overcoming these intermittency issues can add further expenses (The Japan Times, 2024).
Research and Development
There is ongoing research and development focused on improving carbon capture technology and reducing costs. The U.S. Department of Energy has invested over $4 billion in carbon capture and storage research since 1997 (https://www.eenews.net/articles/epa-says-carbon-capture-is-within-reach-utilities-arent-biting/). Key areas of R&D include:
Reducing the energy requirements of carbon capture systems. Current systems require significant amounts of energy to operate. MIT researchers have developed a new electrolyzer that can capture CO2 while also generating electricity, providing a more energy efficient approach (https://news.mit.edu/2023/study-suggests-energy-efficient-route-capturing-and-converting-co2-0906).
Developing new materials and processes to lower the cost of carbon capture. This includes new solvents, sorbents, and membrane materials that can selectively separate CO2 from flue gas emissions.
Optimizing system integration and process configuration to improve overall efficiency and reduce parasitic energy losses.
Utilizing waste heat and developing thermal cycles to reduce energy penalties.
There is still significant room for innovation and cost reduction in carbon capture technology. Continued R&D to improve efficiency and lower costs will be critical for wider deployment and adoption.
Regulatory Landscape
Government policies and regulations have a major impact on the development and adoption of carbon capture technologies. According to the International Energy Agency, “clear and predictable regulation will be essential in enabling investment in CCS [carbon capture and storage]” (A Policy Strategy for Carbon Capture and Storage).
In the United States, the Bipartisan Infrastructure Law passed in 2021 provides tax credits for carbon capture projects, which helps offset the high capital costs (Legislation – Carbon Capture Coalition). The 45Q tax credit provides $50 per ton for geologic storage and $35 per ton for utilization. This policy aims to accelerate deployment of carbon capture to help achieve emissions reductions goals.
However, some experts argue current regulations are not yet sufficient. The Government Accountability Office states “absent technological advances and supportive policies, carbon capture is not expected to be deployed at a scale needed to meet 2050 climate goals” (GAO Report). More policies and incentives may be needed to drive widespread adoption and innovation in carbon capture technologies.
Environmental Impact
Carbon capture and storage (CCS) has many potential environmental impacts that must be considered. When evaluating CCS from a lifecycle perspective, the full emissions from construction, operation, and decommissioning of facilities must be analyzed and compared to alternatives like renewable energy generation.
According to a report by the Center for International Environmental Law (CIEL), the lifecycle carbon emissions of CCS could be even higher than business-as-usual fossil fuel plants without CCS when factoring in fugitive emissions from pipelines, energy required for capture/compression, and embodied emissions in construction materials.
Proponents argue CCS can enable continued use of fossil fuels while reducing emissions. However, investing in CCS could divert resources away from deploying renewable energy at the pace and scale needed to meet climate goals. Some experts warn relying on future carbon removal instead of cutting emissions now is risky and could delay necessary action.
More research is needed to fully understand the lifecycle impacts of existing and emerging CCS technologies compared to renewable energy alternatives. Environmental assessments should inform policies that aim to mitigate climate change in a socially responsible and ethical way.
Conclusion
In summary, carbon capture involves capturing carbon dioxide emissions from industrial sources before they enter the atmosphere. The captured carbon can then be used in various ways, including generating electricity through advanced conversion technologies. While carbon capture shows promise for reducing emissions and providing a secondary revenue stream, it comes with substantial economic and energy costs. More research and development is still needed to improve the efficiency and viability of carbon capture technologies.
Overall, carbon capture alone cannot realistically produce enough electricity to fully replace traditional power plants. The conversion technologies are still too inefficient, costly, and energy intensive to scale up in a major way. However, carbon capture could play a supplemental role in reducing emissions from fossil fuels and providing some additional electricity, especially when combined with enhanced oil recovery. With continued innovation and declining costs, carbon capture may become a more significant part of the energy mix. But for now, other low carbon technologies like renewables and nuclear offer greater potential for clean electricity production.
