Optimization of anaerobic co-digestion of fruit and vegetable waste with animal manure feedstocks using mixture design

Abstract

Optimization of anaerobic co-digestion of fruits and vegetable waste (FVW) with cow manure (CD) and poultry manure (PM) was studied by conducting biochemical methane potential (BMP) tests at different mixing ratios using central composite design (CCD). Findings of this study showed that methane yields of co-digestion tests were improved in comparison to mono-digestion of single substrates. The two optimal responses predicted by mixture design, 0.5 FVW:0.5 PM and 0.54 FVW:0.16 CM:0.3 PM, allowed the maximum methane yields. The analysis of BMP results using Gompertz model has proved that FVW:CM:PM mixing ratio of 0.54:0.16:0.3 yielded the best methane production. This optimal mixture ratio was used to set a laboratory scale digester under mesophilic condition. Results showed that co-digestion of FVW with CM and PM achieved biogas yield of 899 mL/g VS, which is higher than that registered during a control experiment of FVW mono-digestion (399 mL/g VS). Moreover, a high methane percentage was registered during the co-digestion. Accordingly, our finding revealed that co-digestion of FVW with animal manure feedstocks produced 125.3% more biogas yield than mono-digestion of FVW and generated a good quality of digestate.