Chiang Mai Journal of Science

     This research aimed to investigate the three-stage high solid anaerobic digestion (TSHS-AD) at ambient temperature. BMP was conducted at the various substrate to inoculum (S: I) ratios of 2:1, 4:1, and 6:1 on a volatile solid (VS) basis, each of which was conducted at different total solid concentrations (15%, 20%, and 30%). The highest methane yield of 343.97 mL-CH4·gVS^-1 was achieved at 2:1-S: I ratio and 15 %TS. Meanwhile, TSHS-AD operated at S: I 2:1 and 15 %TS (20g-TS/L-R1) provide a maximum methane yield of 316.09 mL-CH4·gVS^-1. The stage separation of TSHS-AD reduces inhibitors in the methanogenesis step. Moreover, it could create a full microbial function in each stage. Accumulation of VFA and semi-continuous feeding have considerable influence in enhancing anaerobic microbes involved in the biogas system. The annual income from biogas has the greatest impact on the investment attractiveness of TSHS-AD, according to the computation of IRR, NPV, and PB. The results obtained in this research could be potentially helpful to scale up the TSHS-AD system.