Use of Carbon Capture Technology to Reduce CO2 Emissions

By Alessandro PiroliniSep 8 2014

Skymine carbon capture facility in Texas, under construction. Image Credits: John Davidson for Skyonic Corporation

Climate change, in particular climate warming trends over the past century, is a global problem which 97% of climate scientists agree is likely due to human activities (NASA). To address this serious threat, energy efficient and low carbon technologies must be developed whilst also ensuring that they are affordable for the general population.

Carbon capture and storage technology is the process of capturing carbon dioxide (CO₂) emissions from power plants generating electricity from fossil fuels and storing it in deep geological formations to mitigate the contribution of fossil fuel emissions to global warming.

Carbon Capturing Technology

Carbon is captured from power plants in a number of different ways. During the combustion of fossil fuels, flue gases containing CO₂ are released by power plants. Post-combustion carbon capture is a process whereby the CO₂ is separated and captured from flue gases via the addition of a filter to the power plants. These filters trap the CO₂ as it travels up a smokestack. It is usually a solvent which can be heated to release water vapor and leave behind a concentrated CO₂ stream.

As an alternative to post-combustion carbon capture, pre-combustion carbon capture involves the separation of CO₂ prior to the burning of the fuel. Solid or liquid fuels, such as petroleum, biomass or coal, that are used to run power plants are first gasified in a chemical reaction at high temperature in the presence of oxygen. Carbon monoxide and hydrogen are then formed. CO is then converted to CO₂ and removed leaving behind pure hydrogen for energy production processes.

The final process is called oxy-fuel combustion carbon capture in which fossil fuels are combusted in the presence of pure oxygen. To control the resulting high temperatures, cooled flue gas containing water vapor and CO₂ is injected into the combustion chamber. Water vapor is then condensed through cooling, and the resulting pure CO₂ stream can be stored in the sequestration site.

From all of these methods, captured CO₂ is transported to suitable storage sites such as unmineable coal seams, depleted oil and gas fields or deep saline formations using pipelines or ships.

Carbon Capture Plants of the Future

Carbon capture technology has been under development for a number of years now. Most recently, Skyonic started construction of the world’s first commercial carbon capture facility, Skymine in San Antonio, Texas.

The facility uses the post-combustion capture method to trap CO₂ which is then treated with caustic soda to produce sodium bicarbonate, hydrogen gas and chlorine gas.

Skymine carbon capture facility in Texas, under construction. Image Credits: John Davidson for Skyonic Corporation

Scheduled to be completed later this year, the plant will capture around 83,000 tons of CO₂ emissions and produce around 160,000 tons of bicarbonate.

Speaking exclusively to AZoCleantech, Stacy MacDiarmid, Director of Communications at Skyonic said "The bicarbonate will be sold for industrial uses — the bicarbonate market is pretty profitable. Sales of the bicarbonate and HCl [hydrochloric acid] from the Capitol SkyMine plant are expected to generate almost $50M annually. That more than offsets the cost of capture, and pays off the construction cost of the plant in about 3 years."

Other carbon capture projects include the Turceni power plant in Romania, where Getica CCS Project Company is going to implement a full chain operational carbon capture and storage system to the already exisiting power plant. This will also employ the post-combustion capture technique and is expectedf to capture 1.5 Mt of CO₂ per annum.

The Summit Power Group is developing a 400 MWe integrated gasification combined cycle for the Penwell coal power plant in Texas. Using this gasification unit, approximately 2-3 Mt of CO₂ will be captured per annum.

Finally another Texas-based coal power plant, W.A. Parish, has a proposed carbon capture system too. NRG Energy is suggested the use of steam to capture CO₂. The company believe that this system is capable of capturing approximately 1.4 Mt of CO₂ per annum.

Capturing the Moment

With U.S. temperatures predicted to increase by 4-11°C by 2100, there is a very obvious need to reduce emissions and promote green technology. Unless drastic changes are made, these temperature changes will cause dramatic variations in our weather including stronger and more frequent storms and increased precipitation throughout the year (EPA). Carbon capture technology may be a lifeline for helping prevent this future from being realised.

Stacy MacDiarmid discussed the future of the carbon capture industry: "I think in the next 20 years we are going to see more Carbon Capture and Utilization technologies, instead of what we think of as traditional CCS [carbon capture storage] with pipelines and underground storage,"

"Starting to think about CO₂ as a raw material for reuse, instead of a liability, is the way we see the industry going," she said.

Currently, the majority of research focuses on carbon capture from fossil-fuel-based power plants, which are the primary source for most CO₂ emissions. Carbon capture technology will be an efficient method to reduce emissions whilst allowing energy needs to be met. Although this technology has been introduced to very few power plants across the world, researchers envision a future where all power plants employ carbon capture units.