Batch anaerobic co-digestion of food waste and sludge: a multi criteria decision modelling (MCDM) approach

Abstract

The present study investigates the application of Multi Criteria Decision Modelling (MCDM) on batch anaerobic co-digestion of kitchen food waste (FW) and the fresh septic tank sludge (STS) for robust output. The batch experiment was carried out at a temperature of 37 ± 2 °C. Different ratio of FW and STS (FW: STS:100:0; 75:25; 60:40; 50:50; 25:75; 0:100) were adopted based on volatile solid (VS) basis as co digestion strategy for 90 days digestion period. Results revealed that experimentally, mono-digestion of FW showed maximum biogas yield (544 ± 65 mL/g VS) followed by blending ratio of 75:25 (FW: STS). However, mono-digestion of STS showed only 150 ± 15 mL/g VS of biogas yield and also showed negative effect on co digestion with FW for every blending on VS basis as STS was high in minerals. MCDM revealed that the FW is the best possible alternative amongst the other blends with STS considering pH, chemical oxygen demand, VS reduction, alkalinity, C/N and biogas yield as output.