Thermochemical Characterization and Combustion Performance of Crescentia cujete Shell as a Renewable Biomass Feedstock for Sustainable Charcoal Production

Abstract

The growing demand for sustainable and renewable energy sources has intensified the search for underutilized agricultural residues that can serve as alternative biomass feedstocks for charcoal production. Crescentia cujete (calabash) shell is an abundant lignocellulosic by-product whose thermochemical properties remain largely unexplored despite its potential for renewable energy applications. This study evaluated the suitability of calabash shell as a biomass feedstock for sustainable charcoal production through an integrated assessment of its moisture characteristics, thermal degradation behavior, carbonization performance, and combustion properties. Mature calabash shells were cleaned, sun-dried, carbonized under oxygen-limited conditions, and characterized using oven-drying moisture analysis, thermogravimetric analysis (TGA), and comparative water-boiling tests against coconut shell charcoal and commercial wood charcoal. The biomass exhibited a low moisture content of 6.71%, indicating favorable conditions for thermochemical conversion. Thermogravimetric analysis revealed the characteristic three-stage degradation behavior of lignocellulosic biomass, comprising moisture evaporation below 120 °C, rapid decomposition of hemicellulose and cellulose between 300 and 400 °C, and gradual lignin degradation up to 800 °C, resulting in a residual mass of approximately 21.5%. These findings demonstrate the thermal stability of calabash shell and its ability to produce substantial carbonaceous residue during pyrolysis. Combustion evaluation showed that calabash charcoal achieved the shortest ignition time (3 min) among the tested fuels and boiled 80 mL of water in 11 min 41 s, outperforming commercial wood charcoal but remaining less efficient than coconut shell charcoal. The combined thermal and combustion results demonstrate that Crescentia cujete shell is a promising renewable biomass resource for charcoal production and agricultural waste valorization. This study provides baseline thermochemical data for an underexplored biomass feedstock and supports its potential application in decentralized renewable energy systems. Further investigations involving calorific value determination, emission analysis, and process optimization are recommended to facilitate its large-scale utilization.