In recent years, the concept of CCS technologies has expanded and now commonly refers to a portfolio of carbon capture technologies. Direct carbon capture, or direct air capture (DAC) as it is commonly known, is accomplished by sequestering carbon out of the air, along with other greenhouse gases, and then the captured gases can be stored; or used to enhance the production of hydrogen or synthetic gases/fuels. Direct carbon capture is being tested in demonstration phases, and is not a large scale commercially available technology yet (although on a small-scale, DAC projects are operation in a few cases globally). DACCS stands for direct air carbon capture and storage, and is a potential future carbon negative technology/ technology to remove CO2 & other GHGs from the atmosphere; as it sequesters carbon from the air, similar to how trees sequester carbon.
Carbon capture and utilization (CCU), like direct carbon capture, implies that the captured carbon is used for productive purposes; such as the aforementioned enhancement of alternative fuels, enhanced oil recovery (EOR), or other industrial/commercial uses (see more details about this below). Carbon capture utilization and storage (CCUS) is another term that is frequently used. CCU/ CCUS is used with the production of energy from fossil fuels, just like CCS, as these are all just terms for essentially the same set of technologies in the CCS technological portfolio.
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. Therefore (theoretically it must be said, because there is no large-scale BECCS plant commercially operational yet), carbon is sequestered from the atmosphere in the biomass, used to create energy, and the resulting carbon from the biomass energy production is again captured In the CCS process. This article will mostly focus on the term referring to the original technology; CCS – carbon capture and storage/sequestration.
Carbon Capture and Storage (CCS)
Conversations focusing on implementing sustainable technologies to fight anthropogenic climate change focus heavily on renewable energy sources, with solar and wind energy; and clean energy solutions like energy storage, electrifying HVAC systems, and electrifying vehicles, dominating the priority list of 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 carbon capture and storage (CCS) and integrated gasification combined cycle (IGCC) systems.
One of the simplest means of utilizing existing fossil fuel infrastructure in a less carbon-intensive manner; the process of CCS turns dirty fossil fuel sources into cleaner energy sources. CCS is a simple, albeit costly, technology. CCS helps fight climate change by vastly reducing greenhouse gas emissions (GHGs) from energy generation. There are a wide variety of potential uses for the CO2 captured in the CCS process.
The process of carbon capture and sequestration (CCS – also known as carbon capture and storage) 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. Methods vary for the “capture” phase of CCS, although CO2 is often captured post-combustion.
Although CCS can be used with any energy generation process that produces CO2 emissions (including coal), it has been demonstrated often with natural gas combined cycle; but CCS even (potentially) will be used with biomass (bioenergy with carbon capture and storage [BECCS]; a technology that is still in various stages of R&D). An exciting potential future use of CCS as far as future climate change mitigation technological pathways to help the world reach carbon neutrality, is CCS with bioenergy production (bioenergy with CCS – commonly known as BECCS).
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 captured in the CCS process can also be simply used in various industrial purposes and production of various manufactured goods, instead of shipped to a storage location. Carbon dioxide can be transported to industries for use with mass produced goods like soda, or for use in oil development in a process known as enhanced oil recovery. Ultimately, CCS reduces GHGs by up to 90%, whether the CO2 is used for industry or stored deep underground.
Worldwide, there are about 19 large-scale CCS power plants in operation (a total of 51 CCS plants globally – 19 in operation…and 32 in various stages of development). Although the high cost of CCS keeps this technology from taking off worldwide, there are attempts being made to remove the barriers of high cost from the progress of CCS. With continued research and development, the cost of CCS is steadily dropping, making this technology more likely to have a larger market share in the future.
Integrated Gasification Combined Cycle (IGCC)
Although the term “clean coal” is often met with a snicker, IGCC technology is a promising means of making the idea of clean coal a less emissions-intensive reality (especially when also combined with CCS technologies). Essentially, the system turns coal into gas, or natural gas into a “cleaner”, less emissions-intensive gas; making it possible to remove all impurities, or “filter” it, including extracting sulfur and mercury. 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 to a combustion turbine generator to create electricity. IGCC technologies incorporate several ideas into one complex cycle; constantly feeding the power plant with the IGCC technologies without heavy carbon dioxide emissions; and without pumping GHGs, sulfur, and mercury into the atmosphere. (For an example of a case study of IGCC with CCS, please see the link from the European Commission below). 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.
IGCC technologies can be used with coal or with natural gas. IGCC with natural gas, especially combined cycle gas turbines (CCGT); and also ideally used with CCS operating in the CCGT power plants- is a hopeful, promising future mix of technologies that theoretically could produce low carbon natural gas (nearly GHG emissions-free) to power the grid. As of today, there are only a handful of such technologies in development stages in demonstration projects globally; and only a small handful of these types of low-carbon gas plants operating at a commercial scale 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 CCS can be used productively, instead of simply stored underground. Again, productive uses for the CO2 sequestered from the CCS procuss 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 and SNG.
Following is a snippet from a PDF on the pros and cons of CCS technologies; from the European Comission. 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 has health and ecosystem benefits, but depletes 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.” FROM – ec.europa.eu/environment/newsalert/pdf
Please also see: Gasification – Creation of Syngas from Fossil Fuels and Low Carbon Sources such as Biogas