Effects of microwave and ultrasonic pretreatment on biomethane production from peat

Peat is abundant and can be used to produce biomethane, a clean energy source that helps reduce greenhouse gas emissions and drive the energy transition. Yet, its natural methane yield is low, making scientific pretreatment crucial for boosting biomethane output. Microwave and ultrasonic pretreatment technologies can promote biomethane production from biomass. Microwave and ultrasonic pretreatment applications in peat methane production need to be explored. The effects of microwave and ultrasonic pretreatment on biomethane production from herbaceous peat were systematically investigated using daily biomethane production, total biomethane production, methane content, humic acid content, glucose content, and acetic acid content. Results showed that the total biomethane production employing microwave and ultrasonic pretreatment was 25.16 and 21.79 mL/g, 2.75 and 2.38 times that of the control group, respectively. Furthermore, compared with the control group, the peat biomethane fermentation system after microwave and ultrasonic pretreatment had a higher methane content ( p ≤ 0.05), higher glucose content ( p > 0.05) and higher humic acid content ( p ≤ 0.05), while a lower acetic acid content ( p > 0.05). These findings demonstrated that microwave and ultrasonic pretreatment facilitated peat biomethane fermentation. Particularly, microwave pretreatment presented a more significant enhancement in biomethane production. This is because microwave and ultrasonic pretreatment can improve the specific surface area of peat, which increases the effective contact area between microorganisms and peat. Meanwhile, microwave pretreatment of peat can reduce the crystallinity of cellulose. The proposal of this study provides a new idea for the green, sustainable conversion of peat resources.