Carbonaceous materials derived from biowastes pyrolysis as efficient and green biogas desulfurization system

Abstract

Abstract The desulfurization performance of carbonaceous material achieved by slow pyrolysis of different kinds of organic raw biomass has been investigated to provide a greener alternative to using activated carbons and contribute to using available resources more efficiently and sustainably. Nine different raw feedstocks and biowastes were used as biomass precursors for biochar production at different pyrolysis conditions. In particular, six of them originated from lignocellulosic biomass (olive pruning, woods pruning, olive stone, spent coffee grounds, solid digestate from cattle, solid digestate from a mix of cattle and pigs), while the other three were from aquatic biomass (crabs’ blue shells, mussels’ blue shells, and microalga Chlorella sorokiniana). The H2S adsorption performances of the different biochar samples were then evaluated compared to commercial activated carbons, the technology currently in use. Moreover, the chemical composition of biochar (before and after H2S adsorption) was investigated to understand better the physical-chemical mechanism that regulated the adsorption. The results showed significant differences in the H2S adsorption capacity of biochars according to their origin (raw biomass) and operating conditions of pyrolysis (temperature and residence time), with the best performance achieved by biochar from olive pruning and microalga Chlorella. Interestingly, a combined mechanism of physio adsorption and chemical oxidation of H2S to elemental Sulphur (S) and sulphate (SO4 2-) was found.