Effects of selected process parameters on product yields from pyrolysis of sweet potato stems

The increasing demand for sustainable energy sources has driven interest in converting agricultural residues into renewable biofuels. This study investigated the effects of selected process parameters on product yields from the pyrolysis of sweet potato stems, an abundant agro-waste material. A fixed-bed reactor was used to examine the influence of temperature and residence time on biofuel yields. Experimental design and optimization were performed using Design Expert 12.0.1.0 software, with pyrolysis temperatures ranging from 350 °C to 550 °C and residence times between 10 min and 30 min. Analysis of variance (ANOVA) indicated that both parameters significantly affected the product yields (p = 0.0001). The optimal condition was achieved at 500 °C and 30 min, yielding a maximum bio-oil output of 29.50 wt%. The produced bio-oil exhibited favorable fuel properties with 54.85% carbon and 21.12% hydrogen contents. Proximate and ultimate analyses of the feedstock revealed a low ash content (0.06 %), high volatile matter (85 %), and substantial carbon composition (47.10 %), underscoring its potential as a biofuel precursor. The findings establish sweet potato stem as a promising and sustainable feedstock for biofuel production, contributing to efficient agricultural waste management and renewable energy generation. Future studies should focus on upgrading and characterizing the derived bio-oil for engine applications.