This January, the first experimental direct air carbon capture (DAC) station in Latin America began construction on the campus of the Pontifical Catholic University of Rio Grande do Sul (PUC-RS) in Porto Alegre. The project results from a partnership between the university and the petroleum firm Repsol Sinopec Brasil. The unit began operations with a reactor capable of removing 15 tons of carbon dioxide (CO₂) per year. The installation is scheduled to be fully operational in July, when annual capture capacity will reach 300 tons of CO₂. Studies are being conducted to assess the gas storage potential of the rock formations in the Paraná basin, one of the regions with the largest CO₂ storage potential in the country.
The oil company is also developing a second project, called DAC 5000, with Senai Cimatec in Salvador, Bahia, designed to capture 5,000 tons of CO₂ per year, which is expected to come into operation in five years. Senai Cimatec is responsible for developing the engineering project and the deployment strategy for the unit. The entire process will be powered by renewable energy, guaranteeing negative emissions. According to engineer Cassiane Nunes, research portfolio and support manager at Repsol Sinopec, the pilot unit will be implemented in the Paraná basin.
Projects that capture carbon directly from the air are classified as negative emission technologies. They differ from other carbon capture, utilization, and storage (CCUS) systems because they are targeted at reducing CO₂ stock already present in the atmosphere, while other technologies aim to release less carbon into the air. Some companies around the world already capture carbon directly from the air, such as the American company Heirloom in California and the Swiss company Climeworks, which has units operating in Iceland.
“While CCUS strategies were designed to reduce greenhouse gas emissions from existing products and processes without, however, achieving neutrality or negative emissions, DAC technology aims to remove carbon emissions that have already occurred. Thus, they aim to reduce the concentration of CO₂ in the atmosphere,” explains engineer Felipe Dalla Vecchia, director of the Institute of Petroleum and Natural Resources at PUC-RS and project coordinator at the university.
DAC systems work with atmospheric CO₂ concentrations around 415 parts per million (ppm), while CCUS systems that capture and separate CO₂ directly at the source of gas emission work with concentrations above 50,000 ppm.
DAC systems consume more energy and have high operating costs, between US$200 and US$700 per ton of CO₂ captured. The price for feasible, large-scale commercial implementation is around US$100 per ton of CO₂ captured, which means that the cost needs to be reduced considerably for the operation to be economically viable. For Dalla Vecchia, accelerating development and reducing technology costs motivated PUC-RS to join the project.
The experimental unit at PUC-RS uses technology created by the German startup DACMa GMbH. It employs the adsorption capture process, in which carbon molecules are retained on the surface of a solid material through chemical or physical interactions. Subsequently, the separation and concentration of CO₂ are furthered through pressure swing systems and an increase in temperature to between 80 and 120 degrees Celsius. To ensure that the entire process will result in negative CO₂ emissions, the experimental unit at PUC-RS will be powered by a solar energy generator with a capacity of 10,000 kilowatt/hours (kWh).
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