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This work focused on the upgrading of non-durable tropical wood species originating from fast-growing plantations of Costa Rica. Modification of such tropical woods with furfuryl alcohol, although ...

Acetylation of softwoods has been largely investigated to increase the dimensional stability and biological resistance of wood. However, the knowledge of this technology has not been applied to tropical hardwood species up to date. The objective of this work was to study the effect of acetylation on nine tropical hardwood species, from forest plantations in Costa Rica, by applying acetic anhydride in three different treatment times (1 h, 2.5 h, 4 h), as well as to evaluate this by Fourier-Transform Infrared Spectroscopy (FTIR). Results showed that weight percentage gain (WPG) of wood varied from 2.2 to 16.8%, withVochysia ferrugineaspecies showing the highest WPG, andGmelina arboreaandTectona grandisspecies exhibiting the lowest WPGs. Tropical woods such asEnterolobium cyclocarpum,Hieronyma alchorneoidesandSamanea samanexhibited statistical differences among treatment times, whereas the rest of the species studied showed no significant differences. In general, the most effective acetylation time was 2.5 h for all the species. The ratio of intensity (RI) from the FTIR spectra was greater at the 1732 cm−1, 1372 cm−1and 1228 cm−1peaks for all tropical species, associated with lignin. A good correlation between the RI of those peaks and WPG was found; the same was also found between all RIs and each other. Meanwhile, RI associated to the hemicelluloses and lignin (1592 cm−1and 1034 cm−1peaks, respectively) showed no correlation with WPG, nor between each other or with the other RIs. Furthermore, it was suggested that RI at 1732 cm−1(associated to acetyl groups C=O) can be considered as a reliable indicator of the degree of acetylation for tropical hardwood species. Finally, it was observed that tropical hardwoods having more suitable anatomical features, like larger vessel diameter, higher ray width and frequency, and lesser deposits such as gums and tyloses in the vessels, resulted in significantly higher WPGs.

This work aimed to evaluate the effect of the precipitation of CaCO3 via subsequential in-situ mineral formation based on a solution-exchange process of two solution-exchange cycles via impregnation with CaCl2 in ethanol and NaHCO3 in water. The effects were investigated in terms of the structure of the wood and the thermal, physical, mechanical, and decay resistance properties of nine species commonly used in commercial reforestation in Costa Rica. The thermogravimetric analysis results showed that the woods with the highest formation of CaCO3 showed a more pronounced signal at 200 °C in relation to untreated/wood; therefore, they were more thermostable. The fire-retardancy test showed that flame time in CaCO3/wood composites was longer than for untreated/wood in half of the species tested, presenting a positive effect of mineralization. Wood density, decay resistance, modulus of rupture (MOR), modulus of elasticity (MOE) in flexion, and MOR in compression were slightly affected by mineralization. Water absorption increased, but it had no negative effect on the dimensional stability. In general, mineralization can be a chemical treatment to increase the dimensional stability and fire resistance of hardwood species without modifying the wood’s physical and mechanical properties.

Light (Tlight), middle (Tmiddle) and severe (Tsevere) torrefaction processes by TGA in woody biomass were evaluated in relation to devolatilization rate (Drate), maximum devolatilization rate (DRmax), temperature at the level of 50% weight loss (T50), rate of weight loss at T50 (R50) and weight loss during torrefaction (Wloss-DT). The relationship between these parameters with cellulose, lignin and extractives content was established. The TGA and devolatilization curves showed that DRmax was of 4.16, 1.80 and 0.70%/min for Tlight, Tmiddle and Tsevere respectively. Wloss-DT in Tlight ranges between 3 and 6%, between 9 and 14% in Tmiddle and from 11 to 16% in Tsevere. G. arborea showed the highest Wloss-DT, with 29.10% for Tsevere and C. Lusitania and T. grandis the lowest Wloss-DT, with 15% for Tsevere. The duration of Dmax was of 5 min in Tlight and Tmiddle and 6 min in Tsevere. Cellulose, lignin and carbon presented statistically significant correlations with R50, T50, Wloss-DT and DRmax. Ash content was correlated with Wloss-DT and DRmax 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.

Torrefaction can increase the energy yield of biomass for better utilization in bioenergy, but chemical changes occur during the pretreatment process. Wood residues of Cupressus lusitanica, Dipteryx panamensis, Gmelina arborea, Tectona grandis, and Vochysia ferruginea were torrefied for three different time periods (8, 10, and 12 min) and three different temperatures (200, 225, and 250 °C). The mass loss, net calorific value, ash, volatiles, lignin, cellulose, extractives, and infrared spectra were evaluated. The results showed that the mass loss in torrefied biomass varied between 10% and 70%, ash content varied between 0.19 and 7.00%, and volatiles content varied between 63 and 85%. Net calorific value values varied between 17 and 23 MJ/kg, increasing with the increased torrefaction temperature. Cellulose varied between 49.85 and 67.57%. Lignin varied between 27.33 and 41.09%. The extractives varied between 3.70 and 16.86%. The change in the ratio of intensity (RI) for the bands identified using FTIR analyses showed that large changes occurred in hemicellulose components. The multivariate analysis showed that lignin, ash, extractives in hot water, volatiles, and mass loss were the variables that contributed most. The analysis of all these variables showed that torrefaction at 250 °C for 12 min presented the greatest biomass degradation. Torrefaction at 200 °C and 225 °C for 8, 10, and 12 min was optimal for thermal treatment of the biomass of these woody species.

La torrefaccion y peletizacion se han estudiado en la generacion de calor a partir de residuos lignocelulosicos, para incrementar las propiedades energeticas del material. El objetivo del presente trabajo fue torrefaccionar aserrin de Gmelina arborea y Dipteryx panamensis a 200 °C en tres tiempos: 0, 15 y 20 minutos. Con las biomasas obtenidas se fabricaron pellets de 6 mm de diametro y se evaluaron sus propiedades fisicas, el poder calorico, la densidad y la propiedad mecanica de resistencia a la compresion. Ambas especies presentaron caracteristicas fisicas similares con respecto al diametro (0.50 mm), longitud (21.50 mm) y porcentaje de absorcion de agua (6.00 %). El poder calorico aumento de 9,749 kJ·kg-1 en la biomasa sin torrefaccionar a 18,126 kJ·kg-1 en la biomasa torrefaccionada. Los pellets de D. panamesis presentaron mayor densidad y resistencia a la compresion que los de G. arborea . Con base en los resultados, la resistencia a la compresion del pellet disminuye cuando el tiempo de torrefaccion aumenta. Existe correlacion positiva entre la densidad de los pellets y la resistencia a la compresion. La especie D. panamensis presenta mejor comportamiento a la torrefaccion y peletizacion que la madera de G. arborea .