Operational parameters regulate in-situ emissions of volatile organic compounds (VOCs) and greenhouse gases (GHGs) during kitchen waste composting: Linking functional microbial dynamics to emission mitigation.

Emission of volatile organic compounds (VOCs) and greenhouse gases (GHGs) from kitchen waste composting plants causes significant environmental issues. This paper characterized the emission profiles of VOCs and GHGs from KW composting with different operating parameters. Quantitative results showed that emission intensities spanned 7.4-folds (VOCs: 196-1456 μg·m-3) to 8.2-folds (GHGs: 79-647 mg·m-3) between C1 (R1M1A1) and C9 (R3M2A3). Seven categories of VOCs were identified, with the 'Benzene, Toluene, Ethylbenzene and Xylene' (BTEX) group as the most abundant chemical family. Most VOCs (except for esters) and GHGs predominantly emerged post-thermophilic phase and declined as temperatures receded. Orthogonal experiments were performed to ascertain the impacts of parameters on emissions control, and considering emissions, efficiency, and costs, the optimal parameter combination was the C/N ratio of 35, AR of 0.6 L·kg-1DM·min-1, and MC of 60 %. High-throughput sequencing was utilized to identify functional microbes related to the gases transformation across C1 (R1M1A1) and C9 (R3M2A3) composting systems. Acinetobacter drove the initial release of alcohol and acid VOCs, Pseudomonas generated alcohols/sulfides during thermophilic phases, and sustained Bacillus correlated with ketone emissions. BTEX-degraders, represented by Pseudomonas and Sphingomonas, declined post-thermophilically, coinciding with emission peaks. Methanosaeta-dominated methanogens promoted CH4 generation, whereas methanotrophs (e.g., Methylocystis) subsequently converted CH4 through multifunctional metabolism. Autotrophic nitrification (dominated by Nitrobacter) and heterotrophic denitrification (dominated by Bacillus and Pseudomonas) drove N2O generation, which can be regulated through oxygen diffusion and C/N ratio optimization. This paper would like provide theoretical guidance for the in-situ control of VOCs and GHGs in practical KW composting process.