Carbon recycling captures carbon dioxide (CO2) from industrial sources or the atmosphere, transforming it into useful products. This process aims to reduce atmospheric CO2, fostering a circular carbon economy where CO2 is a resource, not waste. It mitigates environmental impact while creating economic value.
The Natural Carbon Cycle
The Earth naturally cycles carbon through various reservoirs and processes. Plants absorb CO2 from the atmosphere, converting it into organic matter and oxygen through photosynthesis. Animals consume these plants, incorporating carbon, and both release CO2 back into the atmosphere through respiration. When organisms die, decomposers break down their remains, returning carbon to the soil and atmosphere. Oceans also absorb significant atmospheric CO2, storing carbon in dissolved forms or as sediments.
This natural balance has been significantly disturbed by human activities, especially since the Industrial Revolution. The burning of fossil fuels releases vast quantities of CO2 that have been stored underground for millions of years, accelerating its return to the atmosphere. Deforestation also reduces the Earth’s capacity to absorb CO2, as fewer trees mean less carbon sequestration. These disruptions lead to an increased concentration of CO2 in the atmosphere, intensifying the greenhouse effect and driving climate change.
Engineered Carbon Recycling Methods
Engineered carbon recycling is often referred to as Carbon Capture and Utilization (CCU). Capture methods include post-combustion capture, which separates CO2 from flue gases after burning fossil fuels, and pre-combustion capture, which processes fuel before combustion to produce hydrogen and CO2. Direct air capture (DAC) removes CO2 directly from ambient air, addressing diffuse emissions.
Once captured, CO2 can be converted into useful products. Chemical conversion reacts CO2 with other substances, often using catalysts, to produce chemicals like methanol, used for plastics. Biological conversion utilizes microorganisms that metabolize CO2 into organic compounds, similar to natural photosynthesis. Electrochemical conversion uses electricity, often from renewable sources, to reduce CO2 into valuable chemicals or fuels. These methods require energy, and their efficiency varies depending on the specific technology and desired product.
Some emerging approaches integrate the capture and conversion steps into one more efficient process, known as “reactive capture and conversion.” This can reduce the complexities and costs associated with transporting and storing CO2 separately. Researchers are also exploring advanced reactor designs and electrocatalysts to enhance selectivity and lower energy consumption of CO2 conversion processes.
Uses for Recycled Carbon
Recycled carbon can be transformed into a diverse array of products, displacing those traditionally made from fossil fuels. One application is synthetic fuels, such as “e-fuels” or “power-to-X” fuels, produced by reacting captured CO2 with clean hydrogen. These provide lower-carbon alternatives for sectors like aviation where other low-carbon options are limited.
Recycled carbon also serves as a feedstock for various chemicals. This includes building blocks for plastics, polymers, and other materials used in everyday products. Companies are developing processes to convert CO2 into bioplastics, which can be used for food packaging or alternatives to leather.
Recycled carbon also finds application in building materials. CO2 can be used in concrete’s curing process, storing it within the material. This reduces emissions and lessens the need for energy-intensive traditional materials. Research also explores producing food products from CO2, with hybrid electrochemical-biological systems showing promise in creating food components more efficiently than natural photosynthesis.