Carbon Capture Technology & Converting CO2 into Something Useful

Existing Carbon Capture Technology

CO₂ capture technology separates CO₂ emissions from the environment and compresses them for storage in a suitable storage location. The compressed CO₂ can be transported via pipeline or by traditional shipping methods. The captured CO₂ can then be stored in abandoned oil and gas fields, deep saline formations, as well as no longer mineable coal seams. The primary reason CO₂ is needed is to reduce emissions generated by industry and power generation, which would allow fossil fuel use to continue for the time being while still generating a significant decrease in CO₂ emissions.

Several technologies are currently being employed in the capture, transport, and geological storage of CO₂. Typically referred to as “capture technologies”, they can be grouped into three categories, depending on the industry targeted. Development of these technologies has primarily focused on the efficiency of removing CO₂ from the other compounds usually emitted by the industrial process.

• Post-Combustion: Post-combustion methods involve the capture of CO₂ from gas streams produced after the combustion of fossil fuels or other carbon-based materials. The post-combustion separation process involves using solvents to separate carbon dioxide out of the gas and capture it. The thermodynamic driving force for this method is relatively low, typically less than 15%. Common applications for this technology include pulverized coal plants and natural gas combined cycle plants.
• Pre-Combustion: This process removes CO₂ from fossil fuels before combustion is completed. The fuel in the process is reacted with either steam, air, or oxygen and converted into a mix of carbon monoxide and hydrogen. The carbon monoxide is then converted to CO₂ and separated from the hydrogen, which can be used to generate power and/or heat. This process performs slightly better in terms of energy efficiency than post-combustion capture; however, while the energy demand is lower, the capital investment is larger due to the more complex installation.
• Oxyfuel Combustion: The oxyfuel combustion process burns fuel using pure oxygen, or a mixture of oxygen and recirculated gas. This produces a flue containing mainly water vapor and a high concentration of CO₂ (80%). Since the nitrogen component of air is not heated, fuel consumption is reduced, and higher flame temperatures are possible. The gas is then cooled to condense the water vapor, which leaves an almost pure stream of CO₂.

Public Perception & Environmental Impact

With any new technology, there is always some public concern, as well as regulatory uncertainty in its initial stages. The primary concern with carbon capture technology is the storage of CO₂ and the potential environmental impact it may cause. While modifications to international legislative provisions have been made recently to accommodate for the offshore storage of CO₂, many apprehensions remain concerning storage liability, monitoring responsibility, and the transport of CO₂. While general frameworks have been adopted in certain parts of the world, discussions are still ongoing in others, like the United States. According to scientists, this is partly due to the mixed public opinion on the technology, believed to be tied to a general lack of awareness. In fact, in several communities where CO₂ storage projects were planned, local stakeholders have shown concern about the risks, leading to protests.

While carbon capture technology and storage can potentially significantly reduce CO₂ emissions generated by industrial installations, it still poses a risk to the environment from possible leaks in transportation pipelines or storage sites. CO₂ leaking from a pipeline entails similar risks to natural gas leaks, though CO₂ is not flammable. Moreover, while not poisonous, it can lead to asphyxiation if the concentration in the air becomes high enough. As such, several countries have established regulatory standards for the transport and permanent storage of CO₂. Negative environmental impacts can be associated with the toxicological impact related to the use of solvents to chemically trap the CO₂ and the energy penalty required to operate the capture unit.

New Discovery

Engineers at the University of Cincinnati have developed a promising new CO₂ conversion procedure that may make the process more economically viable for industries¹. The method comprises an electrochemical system that converts emissions from chemical and power plants into useful by-products that can be used to generate new materials. Utilizing a two-step cascade reaction, this new technique converts carbon dioxide first into carbon monoxide and then into ethylene. Ethylene is an important industrial organic chemical that has been called “the world’s most important chemical”¹. It’s used in the production of a range of plastics from water bottles to PVC pipe and textiles, to manufacture ethylene oxide, polyethylene for plastics, alcohol, and even rubber found in tires and insulation.

The significance of using a two-stage conversion process is that ethylene selectivity can be increased while also increasing productivity in a process that can be applied to various reactions, given its simple electrode structure. In the future, this technique can be used to reduce carbon emissions while also generating a profit for the industry, eliminating one of the main drawbacks of current carbon capture processes. However, the current process, using copper, requires more energy than it produces in ethylene. While great strides have been made in improving the process, more work still needs to be done, though a superior catalyst than copper would likely solve the economic issue.