Biomethane production from Arachis hypogea shells: effect of thermal pretreatment on substrate structure and yield

The complex lignocellulosic arrangement of Arachis hypogea shells is the major hindrance during its anaerobic digestion process. This work emphasizes the application of thermal pretreatment on Arachis hypogea shells before anaerobic digestion. Different temperatures of 90, 100, 110, and 120 degrees C, with 30 and 60 min duration were applied to the substrate and digested in a batch digester for 30 days at mesophilic temperature. The physicochemical characteristics of untreated and treated substrates were examined with scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). SEM analysis showed an improved porosity of Arachis hypogea shells with increased temperature and time. XRD investigation showed a reduction in the value of the crystalline index and supported the breakdown of the crystalline matrix. FTIR analysis depicted the elimination of hemicellulose and lignin. Biomethane yield from the anaerobic digestion of Arachis hypogea shells was increased by 23.96% at 100 degrees C for 30 min. The treatment above this temperature and time decreased biomethane yield to between 16 and 44%. It can be inferred from this work that conventional thermal pretreatment at 100 degrees C for 30 min released the optimum biomethane yield. Therefore, thermal pretreatment improves biomethane yield efficiently during anaerobic digestion of Arachis hypogea shells and can be replicated commercially.

Automated summary

This study focuses on the application of thermal pretreatment on Arachis hypogea shells before anaerobic digestion. The results show that thermal pretreatment can enhance the porosity of the substrate, reduce the crystalline index, and eliminate hemicellulose and lignin. Biomethane yield is increased under specific temperature and time conditions, with the best result achieved at 100 degrees C for 30 min.