Reducing carbon footprint in high H2S emissions: A synergistic microalgal-bacterial solution for sugarcane biorefineries

Abstract

Sugarcane vinasse, a major by-product of ethanol production, poses environmental and health risks due to its high sulfate content, promoting severe hydrogen sulfide (H2S) formation (up to 50,000 ppmv) during acidogenic fermentation. The resulting H2S and high carbon dioxide (CO2) levels in off-gas create serious hazards, often leading to conventional desulfurization systems’ clogging and high maintenance. This study is the first to investigate a Chloroidium-based combined microalgal-bacterial (CMB) system for simultaneous, high-strength H2S abatement and CO2 sequestration from these challenging vinasse fermentation off-gas streams. Utilizing a 14 L bubble column photobioreactor under increasing gas flow conditions, the system achieved 100 % H2S and 98.2 % CO2 removal efficiencies within 72 h, with a maximum H2S elimination capacity of 30.3 gS-H2S m⁻3 h⁻1. A comprehensive sulfur mass balance revealed that up to 99 % of theoretical sulfate was consumed by the consortium for biomass growth, demonstrating efficient sulfur valorization. Performance was sustained by elevated dissolved oxygen (averaging 15.0 g L 1), ensuring complete H2S oxidation to sulfate without inhibitory