Harnessing Oil-Contaminated Soil Microbiomes for Improved Anaerobic Digestion of Cow and Pig Manure

Abstract

Anaerobic digestion (AD) of animal manures for biogas production faces challenges including nutritional imbalance, foaming, and process instability. This study evaluated bioaugmentation with surfactant-degrading microbial consortia and cell-free extracts derived from well-characterized oil-contaminated soils during cow and pig manure digestion. These previously analyzed soils contained distinct microbial communities dominated by Pseudomonas in acidic, high-PAH soils and Bacillus in neutral-pH soils with genetic potential for hydrocarbon degradation. Over 30 days, six treatments were assessed using the Automatic Methane Potential Test System (AMPTS II), with pH monitoring, foaming analysis, and 16S rRNA sequencing coupled with PICRUSt2 functional prediction. Supplementation with microbial consortia and extract markedly increased cumulative biogas outputs (cow manure: 407.76 to 603.28 mL/gVS and pig manure: 403.82 to 627.5 mL/gVS), biomethane by 30–50%, reduced digestion time by 5–6 days, and improved pH stability. Foaming reduction was substrate-specific: extracts reduced foam by up to 60% in pig manure, while consortia reduced it by up to 65% in cow manure. Microbial analysis revealed enrichment of fermentative and syntrophic taxa (Clostridium sensu stricto and Paludibacter) and upregulation of methanogenesis pathways (tetrahydromethanopterin S-methyltransferase). This study illustrates that tailored bioaugmentation utilizing consortia from hydrocarbon-contaminated soils provides an environmentally sustainable method to enhance methane yields, improve stability, and control foaming in manure AD, with outcomes significantly affected by the type of manure and amendment strategy employed.