Microbial electrolysis cell assisted anaerobic digestion system boosted the methane production from polylactic acid by optimizing the methanogenesis pathway

Anaerobic digestion (AD) is a method for disposing of biodegradable plastics, which offers a solution to the worldwide plastic pollution. However, it is not yet relevant to the recycling of plastics due to its limits in reactive energetics and chemical kinetics. A microbial electrolytic cell-assisted anaerobic digestion system (MEC-AD) was used in this work to degrade polylactic acid, and various pretreatment techniques and applied voltages were examined to provide the greatest bio-methane production. Results showed that hydrothermal pretreatment is the most advantageous considering both the cost and efficiency. The methane output in the MEC-AD was greater, according to a further comparison of the methanogenic performance of both system from hydrothermally pretreated polylactic acid. The system produced the most methane when exerted a voltage of 0.3 V, and its incubation period was 0.6 times of shorter than that of the AD system. The methanogen responses for hydrogenotrophic methanogenesis in the MEC-AD system were significantly enriched as a result of the externally applied voltage. MEC-AD produces 1.17 times more net profit than AD system and has a greater energy recovery rate. This study investigated an economical method for treating polylactic acid and offered an innovative proposal for recycling plastic waste materials.