Study of light, middle and severe torrefaction and effects of extractives and chemical compositions on torrefaction process by thermogravimetric analysis in five fast-growing plantations of Costa Rica

Light (T_light), middle (T_middle) and severe (T_severe) torrefaction processes by TGA in woody biomass were evaluated in relation to devolatilization rate (D_rate), maximum devolatilization rate (DR_max), temperature at the level of 50% weight loss (T₅₀), rate of weight loss at T₅₀ (R₅₀) and weight loss during torrefaction (W_loss-DT). The relationship between these parameters with cellulose, lignin and extractives content was established. The TGA and devolatilization curves showed that DR_max was of 4.16, 1.80 and 0.70%/min for T_light, T_middle and T_severe respectively. W_loss-DT in T_light ranges between 3 and 6%, between 9 and 14% in T_middle and from 11 to 16% in T_severe. G. arborea showed the highest W_loss-DT, with 29.10% for T_severe and C. Lusitania and T. grandis the lowest W_loss-DT, with 15% for T_severe. The duration of D_max was of 5 min in T_light and T_middle and 6 min in T_severe. Cellulose, lignin and carbon presented statistically significant correlations with R₅₀, T₅₀, W_loss-DT and DR_max. Ash content was correlated with W_loss-DT and DR_max in all torrefaction condition. Extractives in dichloromethane was significantly in many parameters. We conclude that the torrefaction of different woody species can be optimized as biomass feedstocks with a specific temperature and time of torrefaction.