Influence of alkali pretreatment on morphological structure and methane yield of Arachis hypogea shells

Optimum energy recovery and economical use of lignocellulose feedstocks required an efficient breakdown of their recalcitrance characteristics. This study investigated the alkali pretreatment of underutilized Arachis hypogea shells’ structural arrangement and methane yield. The NaOH pretreatment was carried out with 1%, 2%, 3%, and 4% (w/w), an exposure time of 45 min, 30 min, 15 min, and 10 min, respectively, at an autoclave temperature of 90 ℃. The functional groups and morphological structure of the pretreated and untreated Arachis hypogea shells were investigated with Fourier transform infrared (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) and digested in anaerobic condition at mesophilic temperature. Structural analysis results showed that NaOH pretreatment reduced cellulose crystallinity and altered the functional groups. At the same time, SEM images depicted disruption of the recalcitrant arrangement of Arachis hypogea shells. The methane yield was 217.63 ml/gVS_added, 222.33 ml/gVS_added, 256.78 ml/gVS_added, 219.61 ml/gVS_added, and 151.23 ml/gVS_added. This result showed that NaOH pretreatment improved the methane yield of Arachis hypogea shells and can be replicated at a commercial scale, and other lignocellulose feedstocks with similar structural arrangements can be considered.