Mammarella D., Di Giuliano A., Freda C., De Bari I., Gallucci K., 2024, Upgrading of Biogas to Biomethane by Using
Biochars as CO2 Sorbent in a Pressure Swing Adsorption Device, Chemical Engineering Transactions, 109, 79-84 DOI:10.3303/CET24109014

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Researchers from Italy have explored a novel method to upgrade biogas to biomethane using biochar-based materials as CO2 sorbents. This study focuses on a process called Pressure Swing Adsorption (PSA), which selectively captures CO2 and methane (CH4) from biogas. The biochar materials used in this study were produced through pyro-gasification of vineyard pruning pellets at different equivalence ratios (ER). Two batches of biochar were treated with potassium hydroxide (KOH) and hydrochloric acid (HCl) to enhance their sorption properties.

The team conducted experiments on a laboratory-scale packed-bed rig, testing the biochar’s ability to capture CO2 and CH4 from a synthetic biogas mixture under pressures ranging from 5 to 9 bar. The biochar treated with both KOH and HCl (designated as BC0.30A) exhibited the highest surface area and the greatest sorption capacity for both gases. Notably, BC0.30A demonstrated effective CO2 capture and a promising potential for upgrading biogas to biomethane.

The study’s results indicate that biochar’s sorption capacity generally increases with pressure. However, the selectivity for CO2 over CH4 decreases at higher pressures, except for the material treated only with KOH. Among the tested materials, BC0.30A showed the most favorable performance at 5 bar, suggesting its suitability for future large-scale biogas upgrading applications.

These findings highlight biochar’s potential as a low-cost, sustainable material for biogas upgrading, contributing to renewable energy solutions and supporting circular economy models. Future research may focus on extending the range of biochar materials tested and further optimizing the PSA process for practical applications.