Harnessing Biodegradation Inhibitors for Cleaner Energy: Exploring Thymol and Sodium Fluoride in Sustainable Swine Manure Management

Abstract

This study evaluated the effectiveness of thymol and sodium fluoride (NaF) as biodegradation inhibitors (BIs) in mitigating ammonia emissions from swine manure and their implications on anaerobic digestion (AD) for energy recovery processes. The core findings revealed that both thymol and NaF markedly lowered ammonia levels in swine manure during the 10 days of storage with NaF showing superior efficacy. The application of 50 mg of thymol/g volatile solids (VS) and 50 mg of NaF/g VS resulted in ammonia reductions of 62.1% and 46.7%, respectively, compared to that in the control (15.9 ± 0.6 mg NH₄⁺-N). The exploration of methane production highlighted that at concentrations up to 200 mg/L, neither thymol nor NaF negatively influenced AD, highlighting a dose-dependent relationship between BIs concentration and AD performance. By applying kinetic analysis, the inhibitory concentrations (IC) for thymol and NaF were determined to be IC₃₀ at 462.4 mg thymol/L and 335.8 mg NaF/L, respectively. BIs also significantly altered microbial diversity and its abundance, crucially affecting methane production potential. This research indicated the importance of carefully managing residual levels of BIs in swine manure to optimize the energy recovery process through AD, balancing the need for ammonia emission control without compromising methane output.