Sulfur-enriched biochar as a potential soil amendment and fertiliser

Abstract

Hydrogen sulfide (H2S) is a highly toxic and corrosive contaminant gas co-generated during anaerobic digestion. Studies have shown that biochars have the potential to adsorb H2S and to promote its oxidisation. To date, no studies have investigated the bioavailabilty to plants of the sulfur (S) contained in biochar when used as an S fertiliser. Biochar was packed into the biogas emissions stream to adsorb the H2S being generated. The resulting sulfur-enriched biochar (SulfaChar) and synthetic S fertiliser (control treatment) were amended to potting soils and the growth response of corn (Zea mays L.) and soybeans [Glycine max (L.) Merr.] and nutrient uptake were measured after a 90-day greenhouse study. SulfaChar contained 36.5% S (S element and SO42–), confirming it adsorbed significant amounts of H2S. Compared with the control treatment, SulfaChar amendment significantly increased corn plant biomass, ranging from 31% to 49% but only a slight increase in soybean biomass (4 to 14%). SulfaChar also increased corn plant uptake of S and other macro- (N, P, K, Ca, and Mg) and micro-nutrients (Zn, Mn and B). Our results show that SulfaChar was a source of plant available S, suggesting that SulfaChar is either a supplier of these nutrients or that it promoted their uptake.