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Energy application potential from the abundant biomass residues is inadequately exploited. Over-dependence on forest trees, its negative environmental impacts, and ever-rising energy costs require alternative production technologies including briquetting. The physico-mechanical and combustion properties of binderless and bindered Alstonia boonei sawdust and Theobroma cacao (cocoa) pod briquettes, carbonized in a steel kiln (at 410±5°C, and a heating rate of 4°C/min from the ambient temperature of 25°C), piston-pressed at 9.0 MPa, were studied. The binders were starch, wax, and clay. Starch-bindered T . cacao pod briquettes recorded the maximum bulk density (640 kg/cm 3 ), while basic density was greatest for sawdust/clay briquette (433 kg/cm 3 ). Sawdust/wax briquette produced much Water Resistance Capacity (76.76%) with safer carbon monoxide (CO) emissions (0.67 ppm). A . boonei sawdust/starch briquettes recorded the greatest calorific value (24.023 MJ/kg), least specific fuel consumption (0.0483 kg/l), and slowest burning rate (0.0005 kg/min). All but T . cacao pod/starch and Sawdust/starch emitted CO below the safe air quality Standard of ≤ 6ppm (24h mean). Binderless sawdust, sawdust/starch and T . cacao pod/starch briquettes recorded 47.86, 20.95 and 11.40 μg/m 3 particulate matter (PM 2.5 ) respectively, which are below WHO Air Quality Standard safe for domestic uses. Binderless T . cacao pod produced more harmful CO and PM 2.5 than its non-bindered A . boonei sawdust counterpart. Clay-bindered briquettes were the most durable. Briquetting, ‘a waste-to-energy technology’, enhances bio-residue management for domestic and industrial spaces in the global energy mix.
Glalah et al. (2024) studied this question.