Effect of Alkali-NaOH Pretreatment on Methane Production from Anaerobic Digestion of Date Palm Waste

Anaerobic digestion of the date palm empty fruit bunch is a promising technology for both solid waste management and biogas production. The date palm empty fruit bunch is a lignocellulosic waste that takes more time for degradation and has a low biodegradability, thus pretreatment is needed to improve anaerobic biodegradation. In this study, the substrate was pretreated with different ratios of alkali-NaOH: 6, 18 and 30% (w/w) (ratio weight of NaOH / weight of Volatile Solid) for 10 min at room temperature to evaluate the effect of high alkali concentration on the methane potential and biodegradability. The experiment was conducted in a 5 L batch reactor under mesophilic conditions (37°C). The methane potential of the untreated substrate was 98.5 NmL/gVS. The best methane potential improvement of 104% was achieved in the treatment of 18% (w/w) (204 NmL/gVS) with a biodegradability of 50%. Besides, two kinetic models were used to fit the experimental methane potentials and to explore process parameters (Modified Gompertz and Transference function). The best fit for predicting the parameters of methane production was observed for the 18% (w/w) pretreatment using the transference function, with a maximum methane production rate of 5 NmL/gVS.d.