Microwave vs. alkaline-microwave pretreatment for enhancing Thickened Waste Activated Sludge and fat, oil, and grease solubilization, degradation and biogas production

The effects of microwave (MW) and combined alkaline-MW pretreatments on the co-digestion of TWAS:FOG mixtures with 20, 40 and 60% FOG were investigated. MW pretreatment at a high temperature of 175 degrees C was shown to be the most effective MW pretreatment option in solubilizing TWAS:FOG mixtures and boosting methane yield. MW pretreatment at 175 degrees C resulted in maximum solubilization (%) of 68.2% for the 20%FOG samples and a maximum methane yield that was 137% higher than the control for samples with 60%FOG. The combined alkaline-MW (NaOH-MW) pretreatment at pH 10 proved to be not an effective option for TWAS:FOG pretreatment before the anaerobic co-digestion. Despite the benefits of MW pretreatment on the TWAS:FOG samples, including a significant increase in solubilization, dewaterability improvement, high VS reductions, and high methane yield productions, the energy analysis resulted in negative net energy values for all MW-pretreated samples.