Low-cost hydrogen sulfide removal with biochar and activated biochar

This study investigates commercial biochars’ effectiveness in adsorbing hydrogen sulfide, which serves as a low-cost addition to biochars’ main purpose such as carbon sequestration and removal of hazardous compounds. Four biochars (BC) produced from garden waste (GW), municipal sewage sludge (MS), wheat straw (WS), and digested fibers (DF) from anaerobic digestion were collected from three novel pyrolysis plants in Denmark and Sweden. Samples were tested before and after steam activation (AC). Steam activation improved the samples’ adsorptive ability. For breakthrough at 1 ppm, the best performance was from AC-MS which adsorbed 2.6 ± 0.4 mgH2S g-1 while BC-MS adsorbed 1.2 ± 0.1 mgH2S g-1. For breakthrough at 90 ppm, both AC-MS and BC-MS exhibited high adsorptive abilities by 14.1 ± 0.6 mgH2S g-1 and 12.6 ± 1.7 mgH2S g-1. Steam activation increased GW samples’ adsorptive ability with more than threefold as AC-GW adsorbed 5.5 ± 0.5 mgH2S g-1 and BC-GW adsorbed 1.5 ± 0.1 mgH2S g-1. MS and DF had high concentrations of metals and other elements known to adsorb hydrogen sulfide such as Ca, Cu, Fe, and Zn. GW had high carbon content and high surface area. The study shows that various types of low-cost biochar with another primary focus can adsorb hydrogen sulfide through distinct mechanisms, namely by adsorbing through its porous carbon structure or by adsorbing onto different inorganic elements combined in conjunction with low sulfur content. Still, scaling up needs further investigation as effective adsorbents, such as MS and GW samples, may be to brittle in their current particle form.