Exploring the effects of slow pyrolysis temperature and species on the quality of charcoal from Amazonian woody wastes

The literature lacks information on how the final slow pyrolysis temperature and Amazonian Forest wood species impact charcoal's physical, chemical, and energetical properties. Thus, this study aimed to evaluate the effect of wood species and final slow pyrolysis temperatures on the charcoal quality for the Brazilian steelmaking industry. Wood wastes were sampled from the branches of six tropical hardwoods (Dinizia excelsa, Manikara elata, Caryocar villosum, Couratari oblongifolia, Anacardium giganteum, and Parkia gigantocarpa). Laboratory-scale slow pyrolysis was performed at 400, 500, 600, and 700 °C. The variations were significant for wood basic density (0.420–0.990 g cm−3), lignin content (22.78–40.68 %, based on dry mass - db), and total extractives' content (2.45–12.01 % db). Furthermore, a significant effect of the pyrolysis temperature and wood species on the gravimetric yield of charcoals (31.66–39.41 % db) was confirmed. The greatest higher heating values for charcoal (>31.00 MJ kg−1) were observed for pyrolysis performed above 600 °C for all species, except P. gigantocarpa, which provided charcoal with 31.90 MJ kg−1 at 500 °C. Balancing all variables studied, temperatures between 400 and 500 °C were optimal for charcoal production. For such species, the effect of the raw wood properties overcame the impact of slow pyrolysis temperature.