Biogas production from sugarcane bagasse with South African industrial wastewater and novel kinetic study using response surface methodology

Abstract

In this paper, the anaerobic co-digestion (AcoD) of sugarcane bagasse (SCB) with municipal sludge are evaluated. The effects of these process parameters were evaluated using two different South African wastewaters (WWs) as co-substrates for AcoD in batch mode. The response surface methodology (RSM) based on the Box-Behnken design was employed to design the experimental runs, optimize, and study the interactive effects of the operating parameters; temperature (25-55°C), and the organic loading rate (OLR) of 0.5-1.5 gVS/mL. The analysis of variance (ANOVA) and the response model developed was used to evaluate the data obtained at 95% confidence level with a maximum correlation coefficient (R2) of 0.9995 for SCB with sugar wastewater (SWW). The ramp plot showed desirability performances of 95.9% for SCB with dairy WW (DWW) and 98.5% for SCB with SWW. Maximum biogas yield of 4.98 m3/KgVS (663.30 mL/d) was obtained for the latter. Data obtained from the biogas production were fitted into four kinetic models namely the first order, Chen, and Hashimoto, Dual pooled, and the modified Gompertz. Amongst all, the modified Gompertz was found to be the best fit in all the four substrates combinations with a correlation coefficient value (R2) of 0.996. Results indicated that the Modified Gompertz model could be the preferred model for the study of South African Industrial WW streams for biogas production. Also, the BBD employed proved to be economical and a reliable tool for modeling, optimizing, and studying the interactive effects of the factors for the biogas yield.

Keywords

• Anaerobic co-digestion
• Box–Behnken design
• Biogas yield
• Response surface methodology
• Sugarcane bagasse