VATIS UPDATE Article

Engineers at the University of Ulsan (UOU), Republic of Korea, have found that nitrogen-doped biochar beads made from chicken manure could be an effective, sustainable way to capture carbon dioxide (CO2) from waste gas streams. The most common capture method for CO2 uses amine liquids, but these have a high regeneration cost and can react with other gases in flue gas. Other solid adsorption methods require high pressures or temperatures or are expensive.

Minh-Viet Nguyen and Byeong-Kyu Lee at UOU investigated the use of biochar, which has a very high internal surface area, but usually will only achieve good adsorption capacities at a high CO2 partial pressure. The researchers used nitrogen-doping, also known as amine modification, to improve the adsorption capacity. NH3 groups have been shown to interact with the CO2, increasing selectivity towards it.

Nguyen and Lee used chicken manure, a cheap and commonly-available waste product, as a source of carbon. They first dried the manure then pyrolysed it at 450°C for one hour to produce biochar. The biochar was mixed with a solution of HNO3, then NaOH, before being placed in a reactor at 450°C with ammonia for one hour, producing amine-modified biochar (AMBC). The researchers then mixed this with a natural polymer called α-L-gulopyranuronate, and dropped the mixture into a calcium chloride solution to produce the beads.