A critical review of prospects and operational challenges of microaeration and iron dosing for in-situ biogas desulfurization

Bench-Scale Liquid-Phase Microaeration and Iron Dosing Comparison for In Situ Biogas Desulfurization and Antibiotic Resistance Management in Mesophilic Anaerobic Digestion

“…It should be noted that combining oxygen with biogas is typically viewed unfavorably due to the risk of explosions linked to methane/oxygen mixtures. Despite the amount of pure oxygen dosed for microaeration being very small and may be quickly consumed, it is crucial to acknowledge that the risk of explosion is always present when working with pure oxygen for microaeration in AD, and should not be underestimated, as suggested in the literature. , Therefore, from an operational standpoint, AD facilities generally prefer not to work with pure oxygen for safety reasons, if possible. This makes air injection a more practical and cost-effective solution.…”

“…Microaeration is operated via controlled injection of a small amount of air or pure oxygen into the headspace or liquid phase of digesters. 6 At low oxygen levels, sulfide can be biochemically oxidized to elemental sulfur and/or sulfate. Iron (salts/oxides) dosing is another approach to achieving in situ desulfurization.…”

“…5 These methods are mostly localized within the digester and limit dissolved sulfide conversion to H 2 S. 5 However, microaeration is considered relatively underdeveloped due to its commercial unavailability, lack of estimated costs associated with the maintenance of digesters in case of elemental sulfur deposition, and safety concerns around dosing the incorrect amount of oxygen/air. 6 Although both methods have been widely explored as low-cost alternatives for biogas desulfurization, there is limited information on their systematic comparison for biogas desulfurization and efficacy in removing other contaminants such as mercaptans and siloxanes from biogas.…”

“…Thus, researchers have explored the use of in situ approaches, such as microaeration and iron salt addition, for biogas desulfurization. Microaeration is operated via controlled injection of a small amount of air or pure oxygen into the headspace or liquid phase of digesters . At low oxygen levels, sulfide can be biochemically oxidized to elemental sulfur and/or sulfate.…”

“…Liquid-phase microaeration is often recommended for its ease of operation and control and has been shown to be effective in full-scale applications . Divalent (Fe 2+ ) and trivalent (Fe 3+ ) iron salts are commonly used and can react with sulfide to form iron sulfide precipitates. , As summarized in a recent review report, a few full-scale demonstrations have already been reported for both methods, showing effective H 2 S removal (72–99%) performance. Although most studies focused on mesophilic AD, studies suggested that both methods could be effective for mesophilic and thermophilic AD.…”