landfill metagenome Raw sequence reads

Municipal solid waste (MSW) landfills are regarded as one of the major sources of greenhouse gas (GHG) emissions across the world. An innovative and sustainable biogeochemical cover system that consists of soil, biochar and basic oxygen furnace (BOF) slag is being developed to mitigate fugitive landfill emissions such as methane (CH4), carbon dioxide (CO2) and hydrogen sulfide (H2S). Biochar amended soil can mitigate CH4 emissions by oxidizing CH4 with the help of microbes whereas BOF slag can mitigate CO2 and H2S emissions by adsorption and various mineralogical reactions. However, BOF slag is highly alkaline in nature with pH >12 and the effect of such high pH on the overall performance of biogeochemical cover system is not known. This study aims at analyzing the effect of pH on CH4 oxidation and microbial community structure of methanotrophs in laboratory-based studies of landfill cover soil and cultivated consortia. The soil-suspension and enrichment culture were incubated at pH ranging from 2-12, and rates of CH4 oxidation were measured, and microbial community structure was analyzed using 16S rRNA gene amplicon sequencing. The optimal pH for CH4 consumption rate was found to be 7 in enrichment culture and 7.6 in soil-suspensions. Negligible CH4 consumption at an extreme acidic pH of 2 (enrichment culture) and no consumption at an alkaline pH of 12 (enrichment culture and soil-suspension) was observed. The enrichments showed shift in the microbial community with Type II methanotrophs adapted to acidic pH and Type I methanotrophs, aerobic methylotrophs at pH 4-10. Furthermore, soil-suspensions also showed slight shift in the microbial community dominated by Type I methanotrophs and methylotrophs at pH 7.6-10. Overall, our results demonstrate that at an extreme alkaline pH (~12), CH4 oxidation is inhibited and do not favor the growth of methane oxidizing bacteria (MOB) in the landfill cover soil.