Hydrogen sulfide removal from biogas using biomass-derived naturally alkaline biochars: performance analysis and kinetics

Removing hydrogen sulphide (H2S) from decentralized biogas plants by local upgrading techniques may prove to be an economical option for biogas purification, particularly in rural regions. In the present study, readily available biomass viz. bamboo and banana peel were used to prepare biochar and employed for H2S removal from raw biogas produced via a 3 m3 Deenbandhu model biogas plant. The physical and chemical properties of fresh and used biochars were compared using several analytical techniques such as pH, EDX, FESEM, FT-IR, and XRD. The highest, 89.2% and 87.7% of H2S were removed from the raw biogas using banana peel and bamboo biochar utilizing the packed bed system. Four kinetic models viz. pseudo-first-order, pseudo-second-order, intraparticle diffusion, and Elovich models were fitted to evaluate the kinetics of H2S adsorption on bamboo and banana peel biochar. Kinetic study exhibited that the H2S adsorption for both the biochars followed the pseudo-second-order kinetic model with R2 = 0.99. The high potential of the adsorbents for H2S removal, the ease of availability of raw materials, the simplicity of fabrication and utilization method of the adsorbents renders it as a potential candidate for biogas desulphurization in small scale biogas plants installed at rural areas.