Response surface methodology for anaerobic digestion of waste from poultry slaughterhouse: Optimization of load and hydraulic retention time

Abstract

The anaerobic digestion (AD) study for the valorization of poultry slaughterhouse waste (PSHW) was assessed at laboratory scale and in mesophilic conditions. Different loads, given gradually from 0.5 g VS/L to 3 g VS/L, were used to evaluate the methane production from PSHW via AD. The highest cumulative methane production (CMP) and methane yield (YCH4) were observed for the 2 g VS/L and 1 g VS/L added loads, with values of 566 Nml and 378 Nml/g VS, respectively, in a HRT of 140 h. The efficiency of the process was examined using a response surface method-central composite design (RSM-CCD) to examine the impact of independent variables such as load and HRT on CMP and YCH4. A statistical analysis of variance (ANOVA) was carried out to evaluate the suitability of the developed model. The YCH4 results showed a probability value (P-value) < 0.0001 and a Fisher value (F-value) of 46.92, confirming the suggested model's strong capability. The observed R2 value, adj. R2, and “F-values” indicate that the CMP and YCH4 models are significant. The highest R2 of 0.9710 and an adjusted R2 value of 0.9503 are obtained for YCH4 as a result of the model's fit. The results showed that the experimental data and the proposed model have a significant level of agreement. The optimal CMP and YCH4 values obtained were 343 ml and 224 ml/g VS, respectively, and were achieved with a loading of 1.6 g VS/L and a HRT of 108 h.