Multiple syntrophic interactions drive biohythane production from waste sludge in microbial electrolysis cells

Area of Science:

• Microbial electrochemistry
• Biofuel production
• Waste-to-energy technologies

Background:

• Biohythane, a blend of biomethane and biohydrogen, is a valuable biofuel produced from organic matter.
• Anaerobic digestion of waste activated sludge yields energy but often insufficient for disposal.
• Microbial electrolysis cells (MECs) offer enhanced bioenergy recovery and sludge disposal with higher efficiency.

Purpose of the Study:

• To investigate biohythane production from waste sludge using biocathode MECs.
• To elucidate microbial community interactions and syntrophy in MECs for biohythane generation.
• To compare MEC performance with conventional anaerobic digestion for sludge treatment.

Main Methods:

• Utilized biocathode microbial electrolysis cells (MECs) with alkali-pretreated and raw waste sludge.
• Employed high-throughput sequencing (Illumina Miseq) of 16S rRNA gene amplicons for microbial community analysis.
• Conducted quantitative PCR to target specific microbial populations, particularly methanogens.

Main Results:

• Alkali-pretreated sludge fed MECs (AS-MEC) achieved the highest biohythane production rate (0.148 L·L⁻¹·day⁻¹).
• Alkali-pretreatment and MEC operation significantly enhanced sludge hydrolysis and biohythane yield.
• Identified dominant microbial communities including Geobacter, Clostridium, and hydrogenotrophic Methanobacterium, indicating diverse gas production pathways.

Conclusions:

• Biohythane can be successfully produced directly from waste sludge in biocathode MECs.
• MECs combined with alkali-pretreatment accelerate methanogen enrichment and sludge hydrolysis.
• Syntrophic interactions among microbial communities are crucial for efficient biohythane conversion, positioning MECs as a competitive alternative to anaerobic digestion.