The effect of thermochemical pre-treatment on biogas production efficiency from kitchen waste using a novel lab scale digester

Abstract

The present study is developed for considering the effect of thermochemical pre-treatment on the biogas production process from kitchen waste. Parameters controlled by the experimental setup include mechanical stirring and temperature. Thermochemical pre-treatment included chemical pre-treatment by 3 and 6% (based on TS) NaOH for 1 h and thermal pre-treatment at 60, 90 and 120 °C for 30 min. The data of the production process were imported to SPSS software using a factorial experiment in a completed randomized design (CRD) and were analyzed by developing the logistic model. Based on the results, the effect of thermochemical pre-treatment was significant at a level of 0.05 and the correlation coefficient of the logistic model, on average was R2 = 0.99. And also, according to the results of the logistic model the delay time ( μ ) in the acidification phase also decreases with the increasing of sodium hydroxide and temperature in the thermochemical pretreatment. For chemical pre-treatment, there was a significant difference in the effect of 3 and 6% of NaOH on biogas production such that increasing the NaOH amount from 3 to 6% (at 120 °C) increased the biogas and methane production as 21.39 and 20.74% respectively. For thermal pre-treatment, increasing the temperature from 60 to 120 °C (in NaOH 6%) increased the biogas and methane production by 13.2 and 11.6%, respectively. The maximum biogas and methane production was related to NaOH 6% and temperature 120 °C (206.16 and 121.42 ml/g VS).