Effect of acidic pretreatment on the microstructural arrangement and anaerobic digestion of Arachis hypogea shells; and process parameters optimization using response surface methodology.

Enzymatic hydrolysis of lignocellulose feedstocks has been observed as the rate-limiting stage during anaerobic digestion. This necessitated the need for pretreatment before anaerobic digestion for an effective and efficient process. Therefore, this study investigated the impact of acidic pretreatment on Arachis hypogea shells, and different conditions of H2SO4 concentration, exposure time, and autoclave temperature were considered. The substrates were digested for 35 days at a mesophilic temperature to assess the impact of pretreatment on the microstructural organization of the substrate. For the purpose of examining the interactive correlations between the input parameters, response surface methodology (RSM) was used. The result reveals that acidic pretreatment has the strength to disrupt the recalcitrance features of Arachis hypogea shells and make them accessible for microorganisms' activities during anaerobic digestion. In this context, H2SO4 with 0.5% v. v-1 for 15 min at an autoclave temperature of 90 °C increases the cumulative biogas and methane released by 13 and 178%, respectively. The model's coefficient of determination (R2) demonstrated that RSM could model the process. Therefore, acidic pretreatment poses a novel means of total energy recovery from lignocellulose feedstock and can be investigated at the industrial scale.

Experimental evaluation of the influence of combined particle size pretreatment and Fe3O4 additive on fuel yields of Arachis Hypogea shells.

A smart energy recovery process can achieve maximum energy recovery from organic wastes. Pretreatment of feedstock is essential to biogas and methane yields during the anaerobic digestion process. This work combined particle size reduction with Fe3O4 nanoparticles to investigate their influence on biogas and methane yields from anaerobic digestion of Arachis hypogea shells. Twenty milligrams per litre of Fe3O4 nanoparticles was implemented with 2, 4, 6 and 8 mm particle sizes and a single treatment of Fe3O4 for 35 days. The treatments were compared with each other and were discovered to significantly (p < 0.05) enhance biogas yield by 37.40%, 50.10%, 54.40%, 51.40% and 35.50% compared with control, respectively. Specific biogas yield recorded was 966.2, 1406, 1552.7, 1317.4, 766.2 and 413 mL g-1 volatile solid. This study showed the combination of Fe3O4 with 6 mm particle size of Arachis hypogea shells produced the optimum biogas and methane yields. The addition of Fe3O4 to particle sizes below 6 mm resulted in over-accumulation of volatile fatty acids and lowered the gas yield. This can be applied on an industrial scale.