Production of Activated Carbon from Biochar Obtained by Wet Torrefaction of Chicken Manure as Sole Feedstock, and in Mixture with Sawdust in a Fluidized Bed Powered with Superheated Steam

Abstract

The process of wet torrefaction (WT) in a fluidized bed powered by superheated steam is applied to produce biochar, which can be subsequently processed into activated carbon, as an interesting bioproduct with high specific surface area. In this study, WT process was carried out at a temperature of 300-350 °C using mixtures of chicken manure and pine sawdust. Both the composition of the initial biomass, and the temperature of WT process had a considerable effect on the contents of non-condensable gaseous torrefaction products. Increasing the proportion of chicken manure in the mixture increased processing time from 30 to 46 minutes. Hence, in this work, it is hypothesized that two processes may have taken place concomitantly in the reactor: wet torrefaction of chicken manure and wet gasification of sawdust. Biochar obtained after WT of chicken manure as sole feedstock, and in mixture with sawdust was further activated using potassium hydroxide at a temperature of 750 °C. The activated carbon had following characteristics: specific pore surface area according to BET: 2031-3392 m²/g, and specific volume of pores with a size of less than 2 nm (micropores): 0.592-0.841 cm³/g. Furthermore, the quality of activated carbon in terms of porosity decreased with higher shares of sawdust in the mixture.