Carbon Capture Technologies

Carbon capture can refer to several different technologies. The most common technical term used today is carbon capture and storage (CCS), or CCS can also refer to carbon capture and sequestration.

One means of utilizing existing fossil fuel infrastructure in a less carbon-intensive manner is the process of CCS. CCS turns dirty fossil fuel sources into cleaner energy sources. CCS is a simple, albeit costly, technology.

CCS helps fight climate change by sequestering carbon dioxide (CO2), the most substantial of all greenhouse gas emissions (GHGs), from energy-intensive industries. 

CCS can be integrated into a range of CO2-emitting industries; such as fossil fuel power plants, concrete and steel manufacturing plants, and plants for other industrial processes (listed below).

CCS works to capture CO2 emissions so that CO2 emissions can be transported to a storage site deep underground. CCS can also work to sequester CO2 for use in industrial processes.

So, in addition to capturing CO2 for storage - sequestering CO2 can also result in carbon capture and utilization plus storage (CCU + storage).

Carbon capture utilization and storage (CCUS) is the term for when the captured carbon is used for a productive purpose. The captured CO2 can be stored, or it can be utilized. Captured CO2 is commonly used for enhanced oil recovery (EOR), or other industrial/ commercial uses (see more details about this below). Carbon capture technologies can also be used to enhance the production of hydrogen or synthetic gases/ fuels. 

Two types of carbon capture are pre-combustion and post-combustion capture. Often in pre-combustion carbon capture, fuel sources are gasified, and then CO2 is captured. CO2 is captured before any combustion takes place.

Post-combustion carbon capture separates the CO2 from emissions produced by fossil fuel combustion, and then CO2 is captured. Post-combustion CCS is primarily used in power plants, and pre-combustion CCS is primarily used in other industrial processes.

Although CCS can be used with any emissions-intensive process that produces CO2 (coal power plants and other industrial processes listed below), it has been demonstrated effectively with natural gas combined cycle plants. CCS used with combined cycle gas turbines (CCGT) would ideally be used to create low-carbon gas with natural gas operations.

This is a hopeful, promising future mix of technologies that could produce low-carbon natural gas (nearly GHG emissions-free) to power the grid. However, the high cost of CCS holds CCGT + CCS from being widely commercially available.

"Industrial processes where large-scale carbon capture has been demonstrated and is in commercial operation include natural gas processing, coal gasification, ethanol production, fertilizer production, refinery hydrogen production..." 

"CCS is applicable beyond the energy sectors and can be applied to industrial sources of emissions, such as iron, steel, and concrete, which have limited abatement options."

Ultimately, CCS can reduce CO2 emissions by 90% or more from fossil fuel-intensive industries, whether the CO2 is used for industry or stored deep underground. In practice, CCS is an important measure to reduce global CO2 emissions.

Removing carbon dioxide directly from the atmosphere is made possible by direct air capture (DAC), yet another carbon capture technology.

CCS can also be used with bioenergy. Bioenergy carbon capture and sequestration (BECCS) results in carbon-neutral, or even carbon negative, burning of biomass for energy; as the biomass is theoretically made carbon-free by the process of CCS.

DAC and BECCS are emerging carbon capture technologies, and represent exciting potential future uses of carbon capture. DAC and BECCS are potentially important future climate change mitigation technological pathways to help the world reach carbon neutrality.

BECCS is a technology that is still in various stages of R&D. BECCS can theoretically produce carbon-negative emissions (theoretically it must be said because there is no large-scale BECCS plant commercially operational globally yet).

With BECCS, there is a cycle that results in the net permanent removal of CO2 from the atmosphere. Carbon is sequestered from the atmosphere in biomass, the biomass is used to create energy, and the resulting carbon from the biomass energy production is again captured in the CCS process.

DAC is accomplished by sequestering carbon dioxide directly out of the air. DAC is being tested in demonstration phases and is not a large-scale commercially available technology yet (although on a small scale, DAC projects are operating in a few demonstration projects globally). DAC sequesters carbon from the air similar to how trees sequester carbon.

Carbon-intensive industries that should consider investing in and using carbon capture technology include fossil fuel power plants & oil/ gas refineries, fossil fuel-intensive product manufacturing companies, and cement and steel manufacturing companies.

***UPDATE: Although carbon capture is not yet a technology that is widely commercially available, as of 2023, there are about 40 commercial-scale CCS operations worldwide, with 50 more projects that are currently in various stages of development and aiming to come online this decade.

This article will mostly focus on the term referring to the original technology, used to burn fossil fuels cleaner; CCS – carbon capture and storage/ sequestration.

Integrated Gasification Combined Cycle (IGCC) is an additional technology that can also be implemented in power plants to burn fossil fuels cleaner (discussed below).

Carbon Capture and Storage (CCS)

Conversations focusing on implementing sustainable technologies to fight anthropogenic climate change and reach net zero focus heavily on renewable energy sources and low-carbon technologies. Solar and wind energy, and clean energy solutions like energy storage, electrifying HVAC systems, and electrifying vehicles, dominate the priority list of climate solutions.

However, there are other options available that work by upgrading current fossil fuel energy generation systems to harness the power of fossil fuels without heavy carbon dioxide emissions, such as CCS.

The process of CCS begins with the "capture" of CO2 from fossil fuel power plants (or potentially any GHG emissions-intensive energy generation plant).

The next steps involve compressing the CO2 gas, transporting it; and ultimately injecting the CO2 deep into the earth, or sequestering the CO2 for industrial use, where it also won't enter the planet's atmosphere.

The CO2 captured in CCS can be transported to a CO2 storage site, and then injected through a pipeline to a subterranean geological formation, several thousand feet below the surface.  In cases where pipelines are impossible, CO2 can also be transported to a storage site via ship. CO2 storage sites can be established under the ocean floor, as well as in subterranean caverns on land.

CO2 captured in the CCS process can also be used for various industrial purposes and the production of manufactured goods, instead of shipped to a storage location.

There are a wide variety of potential uses for the CO2 captured in the CCS process. Carbon dioxide can be transported to industries for use with mass-produced goods like soda, or use in oil development in a process known as enhanced oil recovery. 

Integrated Gasification Combined Cycle

IGCC can turn the production and use of coal (primarily) into a cleaner operation (IGCC can also be used with petroleum, biomass, and other carbon-based fuels). IGCC technology is a promising means of making fossil fuels a less emissions-intensive reality (especially when also combined with CCS technologies).

Essentially, IGCC technologies turn coal into a gas form creating a "cleaner", less emissions-intensive fossil fuel - synthetic gas. IGCC technologies make it possible to remove impurities, or “filter” fossil fuels, including extracting sulfur and mercury (as well as CO2).

The gasification and cleansing process produces steam, which in turn fuels the overall operation of the fossil fuel power plant, including the gasification and cleansing process itself. The cleaner gas is then sent (as well as steam) to combustion turbine generators to create electricity.

IGCC technologies incorporate several ideas into one complex cycle; constantly feeding the power plant with fuel and steam without heavy carbon dioxide emissions. IGCC does this without pumping other GHGs and pollution, like sulfur and mercury, into the atmosphere.

As with CCS, the high costs of IGCC technologies are holding it back from large-scale development; and, as a result, there are only a limited number of commercial-scale IGCC plants globally. (For an example of a case study of IGCC with CCS, please see the link from the European Commission below).

As of today, there are limited real-world examples of such technologies that are actually used in combination (IGCC + CCS), in demonstration projects globally; and only a small handful of these types of low-carbon gas plants operating anywhere worldwide.

CCS and IGCC are two viable options for combating global warming and creating "clean" (or more accurately - "cleaner") fossil fuel power plants. Despite the initial upfront costs of CCS and IGCC, current power plants utilizing these methods report high levels of success and dropping costs over the lifetime of the operation; these positives are in addition to the environmental benefits of removing CO2 from the atmosphere.

Additionally, the CO2 captured with IGCC + CCS can be used productively, instead of simply stored underground. Again, productive uses for the CO2 sequestered from the IGCC + CCS process include enhanced oil recovery, and use with manufactured products; and both CCS and IGCC technologies demonstrate promise in the enhancement of alternative fuels, such as hydrogen.

Following is a quote from a PDF on the pros and cons of CCS technologies; from the European Commission.

Among the benefits listed are the human and planetary health benefits of CCS technologies; such as the reduction of GHG emissions from energy generation, and resulting ecological and public health benefits. Among the cons of CCS is that implementing CCS technologies for fossil fuels, and even for bioenergy sources, still results in the depletion of natural resources>>>

"CCS is seen as a greener way to operate power stations, whilst ensuring an energy supply, allowing society time to make the transition to a low-carbon future. Nevertheless, energy is required to drive the CCS technology...

This study used life cycle impact assessment modelling...from three systems of power stations fitted with CCS technology: a pulverised coal (PC) combustion plant; a natural gas combined cycle (NGCC) power plant with post-combustion CO2 capture, and a coal-based integrated gasification combined cycle (IGCC) power plant with pre-combustion CO2 capture. The captured CO2 was assumed to be transported 300 km by pipeline and injected into a storage site beneath the seafloor.

The study suggests that CCS produces climate change benefits as a result of reduced CO2 emissions. These benefits significantly reduce climate-related damage to human health, by 74% for PC, 78% for IGCC, and 68% for NGCC power plants with CCS, compared with conventional power plants without CCS."

[quote from  -  ec.europa.eu/environment/newsalert/pdf]

Please also see: Gasification - Creation of Syngas from Fossil Fuels and Low Carbon Sources such as Biogas