Efficient start-up of anaerobic methanogenesis process for kitchen waste biodegradation utilizing polyurethane sponge

Area of Science:

• Environmental Science and Engineering
• Biotechnology
• Microbiology

Background:

• Delayed start-up of anaerobic digestion (AD) for kitchen waste (KW) hinders overall process efficiency.
• Organic fillers have shown promise in enhancing anaerobic wastewater treatment, prompting investigation for oily solid waste treatment.

Purpose of the Study:

• To compare the efficacy of four fillers—polypropylene (PP), high-density polyethylene (HDPE), expandable polystyrene (EPS), and polyurethane sponge (PUS)—in optimizing the start-up phase of KW-AD.
• To elucidate the microbial mechanisms underlying filler-mediated improvements in AD performance.

Main Methods:

• Comparative analysis of four different organic fillers (PP, HDPE, EPS, PUS) during the start-up of KW-AD.
• Assessment of methane production, acetate concentration, and microbial community structure (including bacterial and archaeal populations).
• Determination of the optimal dosage of the most effective filler (PUS).

Main Results:

• EPS, PP, and HDPE fillers negatively impacted methane production and led to start-up failures, often increasing acetate accumulation and promoting undesirable microbial shifts (e.g., Actinobacteriota).
• Polyurethane sponge (PUS) significantly shortened the AD start-up phase by 46.06% and increased cumulative methane production by 20.99%.
• PUS enhanced the abundance of hydrogen-producing bacteria (Thermotogota) and hydrogenotrophic methanogens (Methanoculleus), indicating a shift towards hydrogenotrophic methanogenesis. It also enriched electrochemically active bacteria (Thiopseudomonas, Defluviitoga), promoting interspecies electron transfer (IET).

Conclusions:

• Polyurethane sponge (PUS) is an effective filler for accelerating the start-up of kitchen waste anaerobic digestion, improving methane yield and process stability.
• The optimal dosage for PUS in the start-up phase was determined to be 2.80 g/g VS, with a minimum threshold of 0.93 g/g VS.
• This study provides insights into filler-modulated microbial community dynamics and offers a theoretical basis for efficient KW-AD start-up.