IEA (2020), The role of CCUS in low-carbon power systems, IEA, Paris https://www.iea.org/reports/the-role-of-ccus-in-low-carbon-power-systems, Licence: CC BY 4.0
Progress with carbon capture in power generation has not met expectations, but new projects are emerging in key regions
Currently, two large‑scale CCUS facilities operate in the power sector, the Petra Nova Carbon Capture project and the Boundary Dam Carbon Capture project, which are both CCUS retrofits to existing coal-fired power plants. At 240 MW, the Petra Nova project in Texas, which has been operating successfully since 2017, is the largest post-combustion carbon capture system installed on a coal-fired power plant. It captures up to 1.4 MtCO2 annually for use in enhanced oil recovery, which uses injected CO2 to reverse the decline in production of mature oil fields and to increase overall extraction.
In December 2019 J-Power began testing at its Osaki CoolGen Capture demonstration project in Japan, capturing CO2 from a 166 MW integrated gasification combined-cycle plant, enlarging the portfolio of capture technologies at operational coal-fired power plants.
Progress on bioenergy in combination with carbon capture has accelerated with Drax’s BECCS pilot project in the United Kingdom, a world-first demonstration capturing CO2 from a power plant fuelled by 100% biomass feedstock. The first pilot commenced capture operations in early 2019 (1 tCO2/day) and a second pilot project was announced in June 2020, set to capture 0.3 t CO2/day from Q3 2020. If the project proceeds to a full-scale operation, it could become the world’s first negative-emissions power station.1
While there are currently no large-scale CCUS gas-fired plants operating, the Oil and Gas Climate Initiative recently announced that a partnership involving several of its member companies will undertake a front-end engineering and design (FEED) study on a gas-fired power plant in the United Kingdom.
Separately, the NET Power 50 MWth clean energy plant in Texas is a first-of-its-kind natural gas-fired power plant employing Allam cycle technology, which aims to use CO2 as a working fluid in an oxyfuel supercritical CO2 power cycle. The NET Power demonstration project started operations in 2018. According to the developers, NET Power could make zero-emissions natural gas-fired power generation competitive with existing power generation technologies. It is also developing the application of Allam cycle technology to coal using coal gasification.
Twenty CCUS power generation projects are currently under development. Eleven of the twenty projects are in the United States; three are in China and the United Kingdom, respectively, as well as one each in Ireland, Korea and the Netherlands. Seven of the projects in development relate to gas-fired power: one involves converting a gas-fired plant to hydrogen, two relate to biomass and waste based power generation, and the remainder plan to apply CCUS to existing or new coal-fired power plants.
The two large-scale CCUS power projects operational today and the 20 in development have a potential combined capture capacity of more than 50 MtCO2 per year.This compares to around 310 MtCO2 captured from power generation in 2030 in the IEA Sustainable Development Scenario, reflecting that carbon capture, utilisation and storage in power is not currently on course.
Power sector CCUS facilities
A broad range of studies identify significant potential to reduce the cost of equipping power plants with carbon capture technologies
A series of studies have highlighted significant potential to reduce the cost of equipping power plants with carbon capture technologies.2 These studies highlight that significant cost reductions can be achieved from one generation of plants to the next through technology refinement and efficiency improvements, as well as capital and operating cost reductions, based on the lessons learned from the plants already in operation.
The operators of the Boundary Dam CCS Facility identified that cost savings of at least 30% are possible for the construction and operation of a similarly scaled CCUS facility, based on the early experiences and lessons learned from the plant’s commissioning and early operation. The subsequent Shand CCS feasibility study (undertaken by the operators of the Boundary Dam CCUS retrofit project) found that a second-generation capture facility could be built with 67% lower capital costs (per tonne CO2), achieving an overall cost of capture of USD 45/tCO2 and a CO2 capture rate of more than 90%.
In a study for the IEA Coal Industry Advisory Board, the International CCS Knowledge Centre (2019) identified a series of opportunities to reduce the cost of retrofitting post-combustion capture at plant level. Their findings are based on the learnings from the two large‑scale CCUS power plants in operation and the 2018 Shand CCS feasibility study. Reductions can be achieved in capital costs, operating costs and CO2 transport and storage costs.
Cost reduction potential for next-generation CCUS projects by cost type
Cost reduction measure
Scaling up the CCUS plant
Improved site layout and modularisation
Increasing capture capacity
Increased efficiency of the host power unit
Optimising CCUS operating envelope
Development of a CCUS supply chain
Reduced amine degradation
Lower maintenance costs
Optimisation of thermal energy
Optimised water consumption
Increased compression efficiency
Transport and storage costs
Siting with complementary partners in industrial CCUS hubs, allowing for shared infrastructure
Capital costs are an important component of CCUS projects and account for more than half of the total cost of capture at the first-generation CCUS retrofit plants in operation. Operating costs for CCUS-equipped plants are typically higher than for unabated plants due to the additional energy required to operate the capture facility. Further operating expenses relate to the consumption of solvents, chemical reagents, catalysts, the disposal of waste products and additional staff needed to run the CCUS facilities. CO2 transport and storage costs form an important cost component of a CCUS project if it requires new CO2 storage or transport infrastructure.
CO2 capture is benefiting from numerous research initiatives
New technologies and improvements are under development for post-combustion, pre-combustion and oxy-fuel combustion capture systems. It is currently unclear which CO2 capture technologies will be the most effective in delivering cost reductions and performance improvements as several are still in the early stages of development and demonstration. IEAGHG conducted a comprehensive assessment of emerging CO2 capture technologies for the power sector. Here is a high-level summary of the main technological developments by capture route:
Post-combustion capture. This capture route separates CO2 from the combustion flue gas. Chemical absorption using amine-based solvents is the most technologically mature CO2 separation technique for power plants and is applied in the two large-scale projects in operation today (Boundary Dam and Petra Nova). Scope exists for cost reductions, mainly due to the use of innovative solvents, standardisation of capture units and large-scale deployment leading to economies of scale and learning-by-doing benefits.
Several technological approaches are on the horizon with the potential to improve post-combustion capture, covering the full range of technological maturity, including sorbents and membranes. Some of these technologies may be able to outperform solvents over time, but each has its own challenges and requires further R&D and demonstration at scale.
Pre-combustion capture. In this capture route, the fuel is processed with steam and/or oxygen to produce a gaseous mixture called syngas, consisting of carbon monoxide and hydrogen (a process referred to as reforming or gasification). Reacting the carbon monoxide with more steam (water-gas shift reaction, [WGS]) yields additional hydrogen and converts the carbon monoxide to CO2. Separating the CO2 from the high-pressure gas mixture provides a gas for the generation of electricity (in a combined-cycle gas turbine or fuel cell).
Coal gasification and gas reforming are both mature technologies. Research focuses on novel technologies that aim to separate the CO2 and hydrogen from the gas mixture during the WGS reaction, including membranes and absorbents. Other research areas include technologies related to coal gasification, such as improved turbines, and fuel cell technology.
Oxy-fuel combustion capture. This capture route uses (nearly) pure oxygen instead of air to combust fuel, resulting in a flue gas composed of CO2 and water vapour . Dehydrating the flue gas results in a high-purity CO2 stream. The oxygen for combustion is commonly produced by separating it from air, often using an air separation unit (ASU). Research efforts focus mainly on improving the efficiency and cost-effectiveness of ASUs as well as those of novel oxygen production technologies, such as oxygen membranes. Chemical looping is another advanced oxy-fuel technology under development; it shows large energy reduction potentials but is still in its infancy.
Supercritical CO2 (sCO2) cycles promise substantial cost and emissions reductions, and have gained particular interest in recent years. While in conventional power plants flue gas or steam is used to drive one or multiple turbines, in sCO2 cycles supercritical CO2 is used, that is CO2 at or above its critical temperature and pressure. Supercritical CO2 cycles offer many potential advantages, including higher plant efficiencies, lower air pollutant emissions, lower investment costs and high CO2 capture rates. Two sCO2 technologies are currently being progressed to an industrial scale by US-based companies:
- NET Power’s 50 MWth clean energy plant in Texas employs Allam cycle technology. The company reports a net efficiency of 59% (lower heating value, natural gas) and electricity costs have been estimated to be around USD 75/MWh. To put this into perspective, the generation cost of a conventional gas-fired combined-cycle power plant is estimated to be around USD 60/MWh (without carbon capture technologies) and USD 85/MWh (with conventional carbon capture technologies) based on a natural gas price of USD 6/MWh. The Allam cycle is a specialised sCO2 system in which sCO2 produced from natural or synthetic gas (from coal gasification) is fired with pure oxygen under pressure. There is interest in demonstrating the coal-based route in the United States too. While this route involves roughly double the CO2 emissions per unit of electricity produced and requires more energy, it has potential in regions of the world where coal is cheap and abundant but gas rarer.
- Clean Energy Systems’ 150 MWe energy plant is at the Kimberlina power plant in Bakersfield, California. Estimations show a net efficiency of around 49% (lower heating value, natural gas) and a cost of electricity of around USD 100/MWh.
Supercritical CO2 cycles are among the technologies supported by the US Coal FIRST programme aimed at developing a new generation of near-zero carbon emissions coal power plants.
Drax (2019), Carbon dioxide now being captured in first of its kind BECCS pilot; Drax (2020), Negative emissions pioneer Drax and leading global carbon capture company – Mitsubishi Heavy Industries Group – announce new BECCS pilot.