Multi-Criteria Decision Support in the Assessment of Microwave Pre-Treatment Effects of Insect Breeding Post-Production Wastes for Enhanced Biogas Production

To release the energy potential of insect breeding post-production wastes (IBWs), an adequate pre-treatment strategy with optimal operational parameters should be chosen. However, such studies yield many variables, often with different units and significance levels. Therefore, multi-criteria decision support might solve such issues. In this study, the microwave pre-treatment was applied as a pre-treatment strategy for IBWs. As operational parameters, input powers of 1000 and 1500 W and temperatures of 80, 110, and 130 °C were chosen. Evaluation of the results was carried out using multi-criteria decision support based on the two methods: Modified Lexicographic Method with Indistinguishability Threshold and the Non-dominated Variants with Dominance Cones. The analysis was conducted for seven criteria representing the final results of the microwave pre-treatment and its energy metrics. Using both methods, which was as follows: S4, S3, S2, S1. The results of multi-criteria analysis indicated that the most beneficial solution in terms of improving biodegradability, effective lignin destruction, and energy usage was an input power of 1500 W and a temperature of 130 °C (variant S4). Experiments on mesophilic anaerobic digestion were corroborated by the results of multi-criteria analyses: for the pre-treated sample (variant S4), the methanogenic potential increased by 12% compared to the raw sample. Additionally, results of energy balance indicated that MR pre-treatment resulted in a positive net energy contribution.