Comparison of Biochar Materials Derived from Coconut Husks and Various Types of Livestock Manure, and Their Potential for Use in Removal of H2S from Biogas

As a potential adsorbent material, loose, porous livestock manure biochar provides a new approach to livestock manure resource utilization. In this study, coconut husks (CH) and livestock manure, i.e., cow dung (CD), pig manure (PM), and chicken manure (CM) were used as biomass precursors for preparation of biochar via high-temperature pyrolysis and CO2 activation. Characterization technologies, such as scanning electron microscopy, Fourier transform infrared spectroscopy, adsorption–desorption isotherms, and pore size distributions, were used to study the microscopic morphologies and physicochemical properties of unactivated and activated biochar materials. The results showed that CD biochar provides better adsorption performance (up to 29.81 mg H2S/g) than CM or PM biochar. After activation at 650° for 1 h, the best adsorption performance was 38.23 mg H2S/g. For comparison, the CH biochar removal performance was 30.44 mg H2S/g. Its best performance was 38.73 mg H2S/g after 1 h of activation at 750 °C. Its best removal performance is equivalent to that of CH biochar activated at a temperature that is 100 °C higher. Further material characterization indicates that the H2S removal performance of livestock-manure–derived biochar is not entirely dependent on the specific surface area, but is closely related to the pore size distribution.