Optimization of Pyrolysis and Selected Physicochemical Properties of Groundnut Shells, Coffee and Rice Husks for Biochar Production

Abstract

Biochar is a solid biofuel that can be obtained from pyrolysis of lignocellulosic feedstocks. In this study, pyrolysis of agricultural wastes (groundnut shells, coffee and rice husks) and their physiochemical characterization was done. Parameters that influenced biochar yields were optimized using response surface methodology and Box-Behnken design. The results obtained showed that rice husks had the highest ash and total solids content of 22.94% and 89.54%, respectively. Coffee husks had the lowest ash and total solids (1.58% and 87.69%) but the highest cellulose content (40.45%). Groundnut shells and rice husks had mean cellulose contents of 28.28% and 20.81%. Moisture content was stable across all the biomass samples with 10.46%, 12.31% and 12.49% recorded for rice and coffee husks, and groundnut shells. Basing on the overall interactive effect of particle size, moisture and cellulose contents, the most optimal interaction that yielded the highest quantity of biochar was found to be at 0.36 mm, 10.18% and 31.51% for particle size, moisture and cellulose contents, respectively. In these interactions, cellulose levels corresponded with groundnut shells as the best biomass material for producing biochar. The study recommends the use of ground nut shells for pyrolysis to produce high yields of biochar for industrial and agricultural applications.