Exploring the Challenge of Carbon Dioxide Capture
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Chapter 1: The State of Carbon Capture Technology
Despite having the technology, we still face challenges in effectively removing carbon dioxide from the atmosphere.
Carbon capture has been a topic of research for over ten years. I completed my PhD in 2013 on a material designed for this crucial application. At that time, fossil fuels accounted for over 70% of the UK's electricity generation. The burning of these fuels emits a variety of gases, and the key issue was to find a method to capture carbon dioxide without also capturing other gases, while using minimal energy. Unfortunately, the technology available at that time consumed so much energy that it rendered power plants economically unfeasible. This meant that more fossil fuels would be burned just to facilitate the carbon capture process, inadvertently releasing more carbon dioxide and driving up electricity prices. Furthermore, even if carbon dioxide could be captured sustainably, the question remained: what to do with this waste gas? No company would choose to capture carbon dioxide only to have to store or dispose of it.
Interestingly, carbon dioxide does have applications, highlighted by a recent shortage in supply. It is a by-product of the fertilizer industry, which produces hydrogen through steam-methane reforming, subsequently used to create fertilizers. The carbon dioxide generated during this process is relatively pure. However, as natural gas prices soared, the costs of producing fertilizers—and consequently carbon dioxide—became unmanageable. This, in turn, affected the food industry, which relies on carbon dioxide for food preservation and carbonated beverages.
The above video explores whether we can effectively capture carbon dioxide from the atmosphere.
If national food security can be so easily compromised, wouldn't it be wise to utilize the excess carbon dioxide that has been emitted for years?
Section 1.1: The Role of Carbon Dioxide in Food Preservation
Media coverage often oversimplifies the role of carbon dioxide in food preservation. This gas is frequently used for storage because it is inert; it remains in a low-energy state and does not react unless significant energy is applied or a catalyst is introduced. While other inert gases like nitrogen and argon are also available, the specific chemistry of carbon dioxide can be beneficial. Notably, carbon dioxide can spoil certain foods; for example, it can taint meat by acidifying moisture. Thus, while carbon dioxide is often part of controlled atmosphere packaging for meat, the gas mixture is crucial.
Moreover, using carbon dioxide in packaging for leafy greens may offer advantages beyond preservation, as plants utilize this gas for growth. While roots, soil, and water are typically necessary, the potential for utilizing carbon dioxide in agricultural contexts is intriguing.
Subsection 1.1.1: The Importance of Gas Purity
The purity of gases and the specific gas mixtures are essential. The processes for purifying gases are energy-intensive, but carbon dioxide from the fertilizer industry is generally pure, making it easier to transport. Since carbon dioxide liquefies at a higher temperature than nitrogen, it could also be cheaper to move.
The beer industry has also been affected by the carbon dioxide shortage. Interestingly, while fermentation generates carbon dioxide, breweries often opt to purchase the gas in bottles instead of capturing it from their processes.
Section 1.2: Challenges in Carbon Dioxide Capture
The material I researched for carbon capture was porous, featuring sites where carbon dioxide molecules could preferentially adhere. However, one major challenge was that other gas molecules also sought to occupy these same sites, making the material less selective. While simple filtration based on molecule size was an option, carbon dioxide has a kinetic diameter comparable to many other gases in the atmosphere.
There are materials that effectively capture carbon dioxide even at low concentrations, such as those found in ambient air. Over a decade ago, one promising technology employed a sorbent—a polymer with a polystyrene backbone and amines—to absorb carbon dioxide. The amines' positive charge attracted carbon dioxide, which could then be extracted by washing the resin with brine. While this technology was successful in laboratory settings, scaling it for practical, cost-effective use in real-world applications remains a hurdle.
The main barrier to widespread carbon capture is not the research on selective materials but rather what to do with the captured carbon dioxide. The energy required to regenerate the liquid amines used in gas scrubbing technologies has historically been too high for commercial viability. Although one company has made strides in energy-efficient regeneration, the question of carbon dioxide's end-use remains. To utilize it in food applications, the gas must meet high purity standards. Until a broader need arises for captured carbon dioxide, it's unlikely that companies will invest in its extraction from the atmosphere or industrial waste gases.
Chapter 2: New Directions in Carbon Dioxide Utilization
The second video discusses the challenges of capturing CO2 from the air.
My research on carbon capture initially targeted coal-fired power plants. However, with advancements in wind and solar technologies, the focus has shifted. Industries such as cement and steel also produce significant amounts of carbon dioxide as a by-product. These sectors utilize carbonates extracted from the earth, burning or reacting them to create valuable products. As we continue to face climate challenges, finding uses for carbon dioxide has become increasingly important.
One promising development involves two large pilot plants in Japan that use carbon dioxide as a feedstock for methanol production. These facilities capture atmospheric carbon dioxide and combine it with hydrogen under high pressure. This method is more direct than traditional steam methane reforming. Methanol, commonly used as a solvent, can also be burned for heat and electricity. Although burning methanol releases carbon dioxide, it can be captured again, creating a circular economy. Additionally, methanol's liquid state at standard conditions makes it potentially easier to transport than gaseous carbon dioxide.
In conclusion, discovering new applications for carbon dioxide is essential for making large-scale carbon capture technologies economically viable.
This narrative is based on a recorded discussion from the podcast, Technically Speaking, which covers the intriguing conversations scientists and engineers have in their labs. These dialogues blend scientific facts with imaginative speculation, often peppered with cinematic references. Episodes are available biweekly on platforms like Apple, Spotify, Amazon Music, Google, Podbean, and more.
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