Co-Pyrolysis of Cassava Peel and Sheep Manure Through Fixed-Bed Pyrolytic Unit for Biochar Application

Abstract

The pyrolysis of agricultural and livestock residues through thermochemical conversion offers a sustainable pathway for waste management and biochar production. This study investigates the co-pyrolysis of cassava peel (CP) and sheep manure (SM) for biochar yield optimization using a fixed-bed pyrolytic reactor. A central composite design (CCD) under response surface methodology was employed to evaluate the effects of pyrolysis temperature (237.87–662.13 °C) and residence time (26.89–48.10 min) on biochar yield for three feedstock ratios: CP/SM (0/100), CP/SM (100/0), and CP/SM (50/50). The physicochemical characterization of the biomass through proximate and ultimate analyses confirmed their suitability for thermochemical conversion. Quadratic models were developed to describe the relationship between process parameters and biochar yield. The statistical evaluation using analysis of variance indicated that the developed models were highly significant (p < 0.0001) with strong predictive capability, yielding coefficients of determination (R²) of 0.9924, 0.9797, and 0.9863 for CP/SM (0/100), CP/SM (100/0), and CP/SM (50/50), respectively. Among the operating parameters, pyrolysis temperature was identified as the most influential factor affecting biochar yield, whereas residence time exhibited a comparatively minor effect. The experimental results revealed that sheep manure produced higher biochar yields due to its higher fixed carbon and ash content, while cassava peel generated relatively lower yields because of its elevated volatile matter fraction. The co-pyrolysis of CP and SM (50/50) demonstrated stable char yields, suggesting beneficial interactions between the two feedstocks. The findings highlight the potential of integrating agricultural residues and animal manure through co-pyrolysis for sustainable biochar production and efficient biomass waste management.