Central Composite Design Optimisation of Banana Peels/Magnetite for Anaerobic Biogas Production from Wastewater

Abstract

Biogas production from wastewater as a function to curb waste and provide energy security has gained worldwide attention. Ensuring the stability of anaerobic digestion (AD) of physiochemical and biological complexity necessitates optimization. In this study, a central composite design (CCD) from a response surface methodology (RSM) was employed to evaluate and optimize the effects of bio-stimulation of banana peels coupled with magnetite on the anaerobic digestion of wastewater to produce biogas. An experimental matrix of 14 runs using the CCD, with two factors (nanoparticle and biochar load) as a function of pH, biogas production, and COD removal by the AD process was operated at a constant mesophilic temperature (37 °C) for 28 days. The analysis of variance (ANOVA) showed that the quadratic models attained were significant (p-values < 0.05) with a high coefficient of determination (R2) values closer to 1. The optimized conditions, including nanoparticle (0.46 g) and biochar (0.66 mgVS/L), resulted in biogas production (19.26 mL/day), pH (7.07), and COD removal (75.17%). This suggests 100% desirability at a 95% confidence level. This finding depicts the trade-off between biogas productivity, biodegradability, and stability of the AD process established for future consideration of using nanoparticles as bio-stimulant.