Inorganic nitrogen-driven Alicyclobacillus biotreatment of high-sulfur bituminous coal: a multiscale approach to...

Alicyclobacillus derived from sewage sludge is employed for biodesulfurization, bioleaching of hazardous elements, and bio-oxidation of the carbon structure of high-sulfur coal. The influence of NO₃^- and NH₄⁺ on these biological processes was examined in the absence of culture medium. The addition of NO₃^- inhibited biodesulfurization, whereas NH₄⁺ enhanced it; the optimal concentration of (NH₄)₂SO₄ was determined to be 6 g/L. Following 30 days of bio-treatment, the pyritic sulfur content decreased by 91.59%, while the bioleaching of Cu, Pb, and Zn resulted in reductions of 52.26%, 39.78%, and 77.19%, respectively. Although the nitrogen content increased from 0.973% to 1.006%, the addition of NH₄⁺ facilitated the biological removal of total polluting elements. Alicyclobacillus and Acidithiobacillus bio-oxidize and degrade organic structures, thereby increasing the disordered carbon structure of coal. During bioleaching, small aromatic rings were consumed, and C_alkyl-C_aryl was formed. Initially, NH₄⁺ promoted microbial growth and enhanced indirect biodesulfurization. The generation of ammonium jarosite may disrupt the pyrite surface and promote bioleaching within the first 6 days, but subsequently reduces the available pyrite surface, thereby inhibiting biodesulfurization. During biodesulfurization, NH₄⁺ is not fully bio-adsorbed and may enhance chemical leaching of pyrite. Bio-treatment increased the calorific value of coal and reduced coal consumption for equivalent heat output. Under a heat output equivalent to 1 t of standard coal, bio-treated coal (NH4-2) reduced CO₂ emissions by 60.53 kg, with reductions of 0.233 t in desulfurized gypsum and 0.094 t in fly ash and slag, demonstrating environmental benefits in terms of CO₂ emissions and solid waste reduction.