Anaerobic digestion of wastes and other organic substrates produces energy-rich biogas. Biochemical methane potential (BMP) is a substrate-specific metric that quantifies the maximum amount of methane that could be produced per unit of substrate. Although numerous guidelines describe BMP determination in detail and several automated commercial systems are available, many studies and peer-reviewed publications continue to report problematic and even obviously inaccurate results. This contribution introduces a comprehensive checklist for BMP testing that consolidates typical requirements, common challenges, potential pitfalls, and useful supporting resources to ensure BMP data are accurate, consistent, and of high quality.
Methane emissions from manure management contribute substantially to greenhouse gas release. Compost biofilters offer a sustainable approach for methane mitigation through the activity of methane oxidizing bacteria. However, thermophilic compost biofilters remain poorly characterized compared with mesophilic systems. This study investigated a full-scale thermophilic compost biofilter treating manure derived gas to evaluate the impact of nutrient availability on methane oxidation performance, and the potential for simultaneous removal of organic micropollutants. Batch experiments at 50 degrees C revealed spatial variation in methane oxidation, with the highest oxidation rates occurring near the gas distribution layer, where microbial biomass and diversity were the highest. Nutrient addition increased methane oxidation by up to 211% in nutrient-limited areas, demonstrating that nutrient availability can constrain biofilter performance. Elemental analyses showed declines of 20%-50% in most nutrients and trace metals, within a year operation, although methane oxidation remained consistently high throughout operation. The compost also degraded several organic micropollutants during methane oxidation, with sulfamethoxazole and benzotriazole achieving up to 78% and 66% removal, respectively, while diclofenac, 2,6-dichlorobenzamide, alachlor-ESA, and dimethyl sulfide showed moderate removal of 8%-28%. Microbial community was highly diverse and metabolically versatile, comprising more than 750 genera. Gas quality profiles yielded strong microbial stratification over time. These findings demonstrate that thermophilic compost biofilters are effective, low-cost systems for simultaneous methane mitigation and removal of selected organic micropollutants, relying on complex microbiomes.
For arsenical gold ores, the efficient oxidation of arsenic is of paramount importance. However, the poor adaptability of microbial strains remains a key bottleneck restricting the efficient application of this technology. This study systematically elucidates the multiscale synergistic mechanisms underlying pyrite-enhanced bio-oxidation of arsenopyrite. An empirical transition point near a liquid-phase bacterial density of 1.1 × 108 cells·mL-1 is associated with the onset of rapid arsenopyrite oxidation under the investigated conditions. The primary oxidative role of Fe3+ and the vital biocatalytic function of the bacteria were clearly delineated. By integrating electrochemistry and energy band theory, the micro-interfacial electron flow between pyrite and arsenopyrite was clarified, which led the effective physical separation of the cathodic half-reaction. Contact angle and zeta potential measurements, together with DFT calculations, suggested a tendency toward preferential microbial attachment to arsenopyrite. Exploratory molecular docking further provided a molecular perspective on possible local contacts between biological components and mineral models. Finally, multi-omics approaches were employed to delve into the crucial role of pyrite in driving microbial community succession and metabolic regulation. Pyrite fostered a robust microbial ecosystem and triggered protective microbial acclimation, which substantially shortened the biological adaptation phase and enhanced the oxidation efficiency. These findings provide a solid theoretical foundation for optimizing the bio-oxidation pretreatment efficiency of arsenic-bearing gold ores and advancing their industrial application.
Perfluorooctane sulfonate (PFOS) accumulates in sewage sludge, yet the metabolic step most sensitive to PFOS during anaerobic digestion remains unclear. Here, substrate-specific activity tests, 13C3-propionate tracing, redox and thermodynamic measurements, metagenomics, and microbial network analysis were combined to investigate how PFOS disrupts propionate-to-methane conversion. At 5.0 mg/L PFOS, cumulative methane production decreased by 12.2%, whereas the maximum propionate degradation rate declined by 47.8%. Under the same exposure, acetoclastic and H2/CO2-dependent methanogenic activities decreased by 18.0% and 21.0%, respectively. The propionate fraction in residual volatile fatty acid (VFA) increased from 22.6% to 51.8%. 13C tracing showed that 13CH4 recovery fell from 41.6% to 13.9% and carbon-transfer efficiency from 45.7% to 26.1%. PFOS also caused H2 accumulation to 4.9 × 10-4 atm, reduced ATP and ETSA by 42.8% and 39.9%, and shifted the ΔG of propionate oxidation to - 1.9 kJ/mol. Metagenomic and network analyses further showed losses of propionate oxidizers, hydrogenotrophic methanogens, related functions, and syntrophic connectivity. PFOS therefore primarily destabilized anaerobic digestion by decoupling syntrophic propionate oxidation.
