Search

Dipteryx panamensis is used in reforestation in Costa Rica and a genetic improvement program has been recently started in the country. The objective of the present study was to study the effect of tree trunk height on the variation of bark, sapwood, heartwood, green density (GD), specific gravity (SG) and green moisture content in green condition (MC-G), in a collection of 8-year-old provenances/progenies planted in the town of Florencia in San Carlos in the northern region of Costa Rica The wood of each of 17 families were studied based on 3 of their progenies, evaluating the properties relative to 0, 25%, 50%, 75% and 100% of the commercial height. According to the results, tree diameter and bark thickness showed no statistical differences in their values across trunk. Significant differences were found in diameter and percentage of heartwood and sapwood between provenances and families. The thickness and percentage of sapwood, thickness and percentage of bark, diameter, pith percentage and percentage of pith eccentricity, showed no significant differences between families. SG and the MC-G presented significant variation between provenances, while GD registered differences at above 25 % commercial height. The variation of physical properties, especially SG, between families within each provenance, shows selection potential for genetic improvement, focusing particularly on the bottom section of the tree.

Paulownia tomentosa is utilized in Costa Rica and other countries for wood production and as feedstock for biomass, though the variation of wood properties for this species is scarcely known. In this work, the specific wood properties of a 5-year-old plantation in Costa Rica were studied. The results showed that bark and pith percentage and wood specific gravity (SG) increased with tree trunk height, while the proportion of heartwood, green wood density and green wood moisture content decreased. The average wood SG was 0.26 and tended to increase from pith to bark. Low wood SG values are related to low mechanical properties, with the advantage that wood shrinkage is low as well, which gives this wood species the potential to be utilized for reforestation purposes in Costa Rica. The gross calorific value of this species was 17809 kJ/kg, which, together with its cellulose and extractives contents, recommend P. tomentosa as a biomass source for energy production.

Steaming and heating as pretreatments before log sawing reduce the negative effects of growth strain (GS). The object of this work was to study the reduction of GS in logs of Dipteryx panamensis from a fast-growth plantation using steaming and heating treatments and evaluate the effects on the lumber quality. According to the results, the maximum temperature in the center of the log was approximately 90°C after 24 hours for both treatments. GS decreased after heating and steaming. The average value of GS for three treatments was 2,085.61 microdeformation units (με) before the treatment, decreasing to average value to1,692.14 με after the treatments. This reduction in turn produced a reduction of crook due to sawing measured in logs and semilogs and a decrease in the values and incidence of crook, bow, twist, and split. Similarly, color parameters (L*, a*, and b*) were statistically affected by the treatment, except for parameter L* in sapwood. In general, wood darkening was observed. Lastly, both treatments applied to D. panamensis logs showed few differences in GS, in crook due to sawing measured in logs and semilogs, and in the values and incidence of crook, bow, twist, and split. Therefore, both treatments achieved GS reduction in D. panamensis lumber.

Alnus acuminata, Vochysia ferruginea, and Vochysia guatemalensis are three low-density wood species used for reforestation in Costa Rica. The goal of this work was to study a thermo-hydro-mechanical densification process and test the characteristics of densified wood of these species. Twelve densifying treatments based on temperature, compression time, and use/no use of steam were tested. The variables of the densification process and the properties of the densified wood were determined. The results showed that the densification percentage was over 80% for wood of A. acuminata and over 70% for wood of V. ferruginea and V. guatemalensis. In the three species, the densification process was influenced by initial density. The influence of temperature during the densification process affected the heating rate and color change. An increase in the modulus of elasticity and modulus of rupture in static bending and in the hardness of the densified wood relative to the normal wood was observed, as well as a clear positive correlation of the properties with final density and maximum load, the latter being highly correlated with initial density. This showed that initial density was significant in the densification process and affects wood properties.

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.

Magnetic wood is a composite material that achieves harmony between both woody and magnetic functions through the active addition of magnetic characteristics to the wood itself. In addition to showing magnetic characteristics, magnetic wood offers low specific gravity, humidity control and acoustic absorption ability. It has potential for broad applications in the fields of electromagnetic wave absorption, electromagnetic interference shielding, furniture, etc. This work reports on the synthesis of Fe

Biochar from agroforestry biomass residues is an alternative source of fertilizers for improving the soil fertility. In Costa Rica, Cedrela odorata is planted in pure plantations and agroforestry systems and different types of substrates are used in the nursery to enhance the growth and performance of the young saplings. The main objective of the present study was to evaluate the growth (in height, diameter, biomass) and distribution of carbon (C), hydrogen (H), and nitrogen (N) for C. odorata plants in a nursery with different application rates of biochar produced from Tectona grandis wood residues. The results showed that the above-measured variables were statistically affected by different application rates of the biochar. The stem diameter, total height, number of leaves, and height increment were statistically significantly higher in the substrate with an application rate of 25–50 tons/ha, in contrast to the 0 and 75 tons/ha application rates, which were statistically the lowest. As for the levels of C, H, and N, there were differences, with the highest values of N and C being in the leaves and stem with the 50 tons/ha application rate and the highest values of H for the 75 tons/ha application rate. The above results showed that applying biochar obtained from T. grandis residues improved soil conditions, resulting in better growth of C. odorata saplings with an application rate of 25 and 50 tons/ha.

Growth stresses are usually present in the fast-growing trees of forest plantations and can be evaluated along stem diameter. Growth stresses are relaxed after tree felling and during sawing and drying, and are manifested in the lumber quality. Different methods have been employed to reduce the effect of growth stresses, such as steaming and heating treatments. Excellent growth and yield in forest plantations of Hyeronima alchorneoides were observed, but they showed difficulties in the primary sawing process and a high incidence of wood warping during the drying process. Steam and heat treatments on the log were used to study their effects on H. alchorneoides sawlog and to evaluate lumber quality. Growth stresses in Hieronyma alchorneoides Allemao trees growing under fast-growth conditions show high and negative effects on the lumber quality (increased warps and splits or checks). Therefore, steaming and heating treatments have been applied to reduce these effects on the lumber. The main objective of the present work was to evaluate the effects of steaming and heating treatments on sawlogs of Hieronyma alchorneoides from the fast-growth plantations to reduce the longitudinal surface growth stress. Twenty-six trees ready for felling in the third thinning were sampled and commercial logs measuring 2.5 m long were extracted from them at different heights. These logs were used to investigate the effect of steaming and heating treatments and the growth stresses were measured before and after treatment. Crooking due to sawing, colour and wards, splits and checks were measured. The results showed that the internal temperature of the logs was approximately 85 °C after the heating treatment, and it was nearly 90 °C after the steaming treatment. It resulted in a reduction of 1500 μe (micro-deformations) before the treatment to 1000 μe after the treatment. Therefore, crooking due to sawing decreased significantly in logs or semi-logs. The parameters such as colour, luminosity (L*), redness (a*) and lightness (b*) decreased in heartwood while L* increased and a* and b* decreased in sapwood, which led to the decrease in quality of the lumber, the magnitude and incidence of the defects in treated logs. As compared to untreated logs, the best performance was obtained with steaming treatment, followed by the heating treatment. The difference found between steaming and heating can be attributed to the temperature in the internal part of the log, which was more than 90 °C in steaming treatment; meanwhile, in the heating treatment, the internal temperature of the log was slightly lower (80–85 °C). Therefore, glass transition can be more easily reached by steaming treatment than by the heating treatment.

Resumen El conocimiento de las propiedades de la biomasa proveniente de clones de Gmelina arborea Roxb en cultivos energéticos en sistemas de corta rotación (SRC en inglés) en Costa Rica es limitado. Los primeros intentos están basados en el uso de clones para la producción de madera, pero plantados en SRC. Así, el presente estudio tuvo como objetivo evaluar las propiedades físicas (peso específico, densidad y contenido de humedad), energéticas (poder calorífico, contenido de cenizas y materiales volátiles) y contenido de carbón de dos clones de G. arborea utilizados para la producción de madera, pero plantados en SRC bajo tres espaciamientos (1,0x1,0 m, 0,75x0,75 m y 1,0x0,5 m), entre 6 y 24 meses de edad. Los resultados muestran que el peso específico básico fue de entre 0,30 a 0,38, la densidad verde de 0,9 a 1,0 g/cm3, el contenido de humedad entre 40 y 70%, el poder calorífico de 18.000 a 20.000 kJ/kg, la cantidad de cenizas fue menor a 4,8% y el contenido de volátiles de entre un 70 a 86%, mientras que el contenido de carbono disminuyo con la edad. Se observaron diferencias entre los dos clones en edades tempranas, pero estás tienden a desaparecer con el aumento de la edad, en especial a la edad de 24 meses, que es cuando se pretende que la plantación sea cosechada, siendo esto una ventaja ya que se tiene una biomasa uniforme si los dos clones son utilizados. Abstract The knowledge of biomass properties from Gmelina arborea clones Roxb in energy crops in short rotation crops systems (SRC) in Costa Rica is limited. The first attempts are based on the use of clones for the production of wood, but planted in SRC. Thus, the present study aimed to evaluate the physical properties (specific gravity, density and moisture content), energy (net calorific value, ash content and volatile materials) and carbon content of two clones of G. arborea used for wood production, but planted in SRC under three spacings (1.0x1.0 m, 0.75x0.75 m and 1.0x0.5 m), between 6 and 24 months of age. Results show that the basic specific gravity was between 0.30 to 0.38, the green density of 0.9 to 1.0 g/cm3, the moisture content between 40 and 70 %, the net caloric value of 18,000 a 20,000 kJ/kg, ash content was less than 4.8 % and the volatile content between 70 and 86%, while the carbon content decreased with age. Differences were observed between the two clones at early ages, but they tend to disappear with increasing age, especially at the age of 24 months, which is when the plantation is intended to be harvested, this being an advantage since we have a uniform biomass if the two clones are used.

The first attempts to establish energy crops in the tropical regi­on using short rotation species are premised on the utilization of clones for wood production. Therefore, the present study is aimed at examining the growth aspects (survival, diameter and tree height), leaf architecture (leaf area index [LAI], number and angle of the branches and sylleptic branches), biomass production, as well as biomass flow at the age of 24 months of two clones of Gmelina arborea in short rotation crops within three spacings (1.0x1.0 m, 0.75x0.75 m and 1.0x0.5 m). The results showed an increment with age, as the diameter increa­sed from 3.00 cm at six months to 8.0 cm at 24 months, where­as the total height increased from 2.00 m at six months to 10.00 m at 24 months. Clone survival varied from 20 to 60 %, whereas the LAI, branch angle and sylleptic branches increased with age. The differences between clones appeared after 12 months. Biomass production was similar between clones, from 6 ton/ha at six months to 67 ton/ha at 24 months, with clone 2 showing greater biomass flow than clone 1. On the basis of biomass pro­duction results and the development of diameter as well as height, clone 1 is recommended for spacing 1.0x1.0 m and clo­ne 2 for spacings 0.75x0.75 m and 1.0x0.5 m.

Densification is one method used to modify low-density woods to make them achieve the hardness required for flooring application. The purpose of this study was to investigate the effect of thermo-mechanical densification with pre-heating in wood of Alnus acuminata, Vochysia ferruginea and Vochysia guatemalensis from, seeking to stabilize and reduce spring-back of the densified wood and evaluate its performance in flooring applications. The results showed that the wood of the three species turned dark. This is because brightness diminished and yellowness and redness increased. Weight loss due to pre-heating was statistically higher in V. ferruginea and V. guatemalensis. The final density and spring-back were statistically similar in the three species. The percentage of densification of A. acuminata and V. guatemalensis were statistically higher than for V. ferruginea and the degree of compression was statistically higher in V. guatemalensis. As for flooring evaluation, the percentage of densification, temperature and time of pre-heating affected the behavior of densified wood flooring. The low percentage of densification and high weight loss in the pre-heating stage caused greater values of wear, wear index, residual deformation, residual indentation for the falling ball indentation test, and more damages in the surface indentation test in wood of V. ferruginea.

Research and implementation of energy crops using short-rotation woody species (SRWC) are increasing in Latin America, especially for biomass production and use in bioenergy. For this purpose, one of the main factors to consider is species assessment. Therefore, the objective of the present study was to evaluate the growth characteristics, the production and distribution of biomass, and the chemical, physical, and energetic properties of the biomass of three-year-old Dipteryx panamensis plantations in SRWC in three different spacings (1.0x2.0 m, 1.0x0.5 m and 1.0x1.0 m) and establish the best spacing condition for this tropical species. The results showed that the production of biomass varies between 1.1 and 42.36 t.ha-1, and that 33-44% of the production are concentrated in the leaves. At three years, the SRWC presented 50% mortality, with a diameter of 4.8 cm at 30 cm-height from the ground, with total tree heights ranging from 5.17 to 6.98 meters. The evaluation of the biomass showed a calorific value between 18.9 and 19.4 MJ/kg, less than 1.81% of ash content and 86% of volatile content. As for the effect of the spacing, the green density of the wood and the moisture content increased with increasing spacing, while spacings of 1.0x1.0 m and 1.0x0.5 m showed the best behaviour regarding annual biomass production. RESUMO A pesquisa e a implementação de plantios energéticos usando espécies lenhosas de rotação curta (SRWC) estão aumentando na América Latina, especialmente para a produção de biomassa e uso na bioenergia. Para esse fim, um dos principais fatores a considerar é a avaliação de espécies. O objetivo do presente estudo foi avaliar as características de crescimento da árvore, a produção e distribuição de biomassa e as propriedades químicas, físicas e energéticas da biomassa de um plantio energético de Dipteryx panamensis de três anos de idade em SRWC em três diferentes espaçamentos (1,0x2,0 m, 1,0x0,5 m e 1,0x1,0 m) e, assim estabelecer a melhor condição de espaçamento para esta espécie tropical. Os resultados mostraram que a produção de biomassa varia entre 1,1 e 42,36 t.ha-1 e que 33-44% dessa produção está concentrada nas folhas. Aos três anos, o SRWC apresentou 50% de mortalidade com um diâmetro de 4,8 cm a 30 cm de altura do solo e com alturas totais de árvores de 5,17 a 6,98 metros. A avaliação da biomassa mostrou um valor calorífico foi de 18,9 a 19,4 MJ/kg, 1,81% de cinzas e 86% de conteúdo volátil. A densidade verde da madeira e o teor de umidade aumentaram com o aumento do espaçamento. Os espaçamentos 1,0x1,0 m e 1,0x0,5 m apresentaram o melhor comportamento em relação à produção anual de biomassa.

The increase in global temperature results in changes in rainfall patterns and can cause structural and functional changes in trees. Each plant is forced to face hydraulic safety limits and adopt a behavior to regulate its water status. The objective of this work was to evaluate the changes in the hydraulic architecture of the xylem of commercial eucalyptus clones in order to distinguish the hydraulic adjustments in a wide gradient of water availability. Eucalyptus urophylla (A1) and E. grandis × E. camaldulensis (C3) clones at six years old at 4 sites in Brazil distributed in a rainfall gradient and in two water conditions were analyzed: control (100% of total local rainfall) and rainfall reduction (RR). Xylem traits were evaluated at annual intervals and averaged over the entire growth period of the seven trees sampled at each site and water condition. The sites influenced the clones, with the greatest effect being the rainfall reduction treatment in C3 on the vessel wall diameter, area and thickness, double wall thickness, conduction area, vessel composition index, theoretical and potential hydraulic conductivities, vessel implosion resistance and vulnerability. The rainfall reduction provided an increase of 12% in vessel density, 8% in the double vessel wall, and 27% in theoretical hydraulic conductivity in the drought-tolerant C3 clone. The vessel wall thickness in the A1 clone was more responsive with a 3% increase in rainfall reduction, with an effect on double-wall thickness and vessel implosion resistance. Other hydraulic adjustment strategies were observed, such as the highest occurrence of tylose and a tradeoff between vessel diameter and frequency for the C3 clone. The greater variation in wood density was explained by variations in the lumen area of the xylem vessels and by vessel implosion resistance.

Micro- and nanofibrillated cellulose (MNFC) was extracted from pineapple stems by acid hydrolysis, then characterized and tested in two concentrations (0.5 and 1.0 wt%) in polyvinyl acetate (PVAc) and urea-formaldehyde (UF) adhesives. The modified adhesives were used to glue three tropical wood species (Vochysia ferruginea, Cordia alliodora, and Gmelina arborea), and their corresponding bond strength resistance was determined. MNFC and the correspondent adhesives were characterized by TGA, FTIR, SEM, TEM, AFM, and viscosity determination. The TGA analysis of MNFC showed three decomposition reactions. The SEM, TEM, and AFM evaluations demonstrated the presence of micro- and nanosized dimensions of particles after the acid hydrolysis of pineapple stems. Adding 1 wt% MNFC to PVAc and UF adhesives increased their thermal stability in similar manner. Viscosity diminished in both modified adhesives with MNFC; however, this reduction did not affect the adhesion properties in the tropical wood tested. MNFC added to PVAc and UF adhesives improved shear strength (SS) of the glue line in the three tropical species tested. The highest SS increase was obtained when adding 0.5 wt% MNFC to PVAc in V. ferruginea, and 1 wt% MNFC concentration in the case of C. alliodora and G. arborea. In the case of UF adhesives, the application of 1 wt% MNFC produced significant differences in SS for the three tropical species studied.

espanolEn construccion de viviendas, las estructuras mas eficientes para soportar las cargas provenientes de techumbres corresponden a las cerchas. Cuando se trata de fabricarlas con madera, un punto importante de estas son las uniones. Actualmente se ha introducido la utilizacion de placas metalicas dentadas para estas uniones, sin embargo, el mercado aun conoce poco de ellas y su posibilidad de utilizacion en casas. Por lo que, este estudio reporta un primer sondeo cualitativo por medio de una encuesta estratificada por publico objetivo, del uso de cerchas de madera con placas metalicas dentadas fabricadas con madera de plantacion en Costa Rica. Fue encontrado que el 100 % de los encuestados considera a la madera como un material viable para la construccion, por almacenar dioxido de carbono y ser un recurso renovable. Ademas, el 90 % de los encuestados, considera que la madera de las plantaciones nacionales es de buena calidad. Sin embargo, solo un 28 % prefiere la utilizacion de las cerchas como elemento estructural en techumbres y el 40 % coincide en que el uso de la placa es una buena opcion tecnologica. Segun este primer sondeo de mercado de la cercha de madera con placa metalica, el 80 % de encuestados estaria dispuesto a adquirirla; dandole un rango de precio entre ¢45 000 a ¢50 000 por cercha. EnglishIn housing construction, the most efficient structures to support the loads coming from roofs correspond to the trusses. When it comes to manufacturing them with wood, an important point of these are the joints. Currently the use of metal plates has been introduced for these unions, however, the market still knows little about them and its possibility of use in wooden houses. Therefore, this study reports a first qualitative survey by means of a survey stratified of the use of wooden trusses with metal plates fabricated with plantation wood in Costa Rica. It was found that 100 % of respondents consider wood as a viable material for construction, for storing carbon dioxide and for being a renewable resource. In addition, most consider that the wood from trees growing in plantations in Costa Rica is of good quality. However, only 28 % prefer the use of trusses as a structural element in roofs and 40 % agree that the use of the metal plate is a good technological option. According to this first market survey of the wooden truss with metal plate, 80 % of respondents would be willing to acquire it; giving it a price range between ¢ 45 000 to ¢ 50 000 per truss.

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.

Resumen La gasificación es un proceso termoquímico en el que materias primas orgánicas se convierten en gases que contienen H2 y CO (gas de síntesis), los cuales pueden utilizarse para obtener productos como electricidad, combustibles y otras sustancias químicas. El proceso se encuentra influenciado por características propias del sistema donde se desarrolla la conversión térmica, las condiciones de operación y las materias primas empleadas. Se simuló un proceso de gasificación de biomasas enriquecidas con hidrocarburos en el que los gases generados son aprovechados para generación eléctrica, con tal de evaluar el uso de dichas materias primas. Se empleó un modelo de gasificación no estequiométrico, la ecuación de estado de Peng-Robinson, así como reacciones de gasificación conocidas. Se consideró un gasificador de corriente descendente trabajando con 22 kg/h de alimentación de mezcla 3:1 biomasa:hidrocarburos, 20 kg/h de aire (agente gasificante), 1 atm de presión absoluta y temperatura de gasificación de 900-1000°C. Los gases generados se componen de 27,44 % H2; 39,79 % CO; 5,73 % CH4; 0,1 % CO2 y 27,01 % N2. La potencia neta del gasificador es 27,82 kW y el consumo de la mezcla 3:1 biomasa:hidrocarburos 0,79 kg/kWh. La adición de hidrocarburos a biomasa mejora las características del gas de síntesis obtenido y disminuye los requerimientos de materia prima para el funcionamiento del gasificador. La mezcla 3:1 biomasa:hidrocarburos es adecuada para el desempeño del proceso, permitiendo aprovechar residuos que de otra manera tendrían que ser dispuestos y tratados, generando beneficios energéticos, ambientales y económicos. Abstract Gasification is a thermochemical process in which organic raw materials are converted into gases containing H2 and CO (syngas), which can be used to obtain products such as electricity, fuels and other chemicals. It is influenced by characteristics of the system where the thermal conversion takes place, the operating conditions and the raw materials used. It was simulated a process of gasification of hydrocarbons-enriched biomass in which the gases generated are used for electricity generation, to evaluate the use of such raw materials. A non-stoichiometric gasification model, the Peng-Robinson equation of state as well as known gasification reactions were used. A downdraft gasifier was considered working with 22 kg/h of mix feed 3:1 biomass: hydrocarbons, 20 kg/h of air (gasifying agent), 1 atm of absolute pressure and gasification temperature of 900-1000 °C. The gases generated are composed of 27.44 % H2, 39.79 % CO, 5.73 % CH4, 0.1 % CO2 and 27.01 % N2. The net power of the gasifier is 27.82 kW and the consumption of the mixture 3:1 biomass:hydrocarbons 0.79 kg/kWh. The addition of hydrocarbons to biomass improves the characteristics of the syngas obtained and reduces the raw material requirements for the operation of the gasifier. The mixture 3:1 biomass:hydrocarbons is adequate for the performance of the process, allowing to take advantage of wastes that otherwise would have to be disposed of and treated, generating energy, environmental and economic benefits.

Mortality, diameter at 30 cm over ground level, height, biomass production, and carbon capture (CC) for different tree components (trunk, bark, branches, and leaves) in two locations in Costa Rica, during their first three years and with three plantation spacings (1.0 &times, 0.5 m, 1.0 &times, 1.0 m, and 1.0 &times, 2.0 m) were obtained for Gmelina arborea Roxb. trees growing in short rotation coppice systems (SRC). In addition, regression models were developed to predict biomass production and CC using location, age, spacing, and their interactions. Biomass production was measured by weight of trees without considering dendrometric variables. Results showed that mortality was lower than 15% for one location, with probable high fertility, and almost 85% for the other location. Diameter and height of trees increased with plantation age in both locations. The highest biomass production and CC were observed in the spacings of 1.0 &times, 0.5 m2 and 1.0 &times, 1.0 m2, with 20 Mg/ha/year and 8 Mg/ha/year, respectively. The models to predict biomass production in trunk with bark, branches, leaves, total biomass without leaves, and CC in trunk, branch, and total biomass were developed using this equation: Y = &beta, 1 + &beta, 2 (location &times, age) + &beta, 3 (age) + &beta, 4 (spacing). The R2 values varied from 0.66 to 0.84, with error from 0.88 to 10.75 and indicators of goodness of fit from 60 to 83%.

In countries like Costa Rica, there is an interest in developing wooden trusses in a versatile and light way. However, there is a key aspect in the behavior of truss connections in this product. Therefore, the present study determines the structural behavior of the truss connections and the displacement, the resistance, the stiffness values and the failure mode of truss connections made with Gmelina arborea and Tectona grandis timber for angles of 0° and 90°; and three types of truss connectors (metal plates, screws and nails), subject to tension and compression loads. The results showed that metal plates show the highest load values with respect to the nails and screws in both species. Likewise, in the design and critical displacement stress, metal plates surpass the nails and screws in both species; and in the two angles. From these stress values, we proposed a model for the prediction of the stiffness for the truss connections of the intermediate angles (30°, 45° and 60°) and the test showed that the prediction was low, the bias was 3%.

A composite between particles obtained residual pallets of Pinus sp and cement was manufactured. Also, three methods were performance for wood particles: hot water washed, unwashed and unwashed with calcium carbonate (CaCO3). Different concrete-wood particle ratios were tested. Curing time was evaluated with ultrasonic pulse velocity (USV) and density of composites. Water absorption, module of rupture (MOR) in flexion, abrasion strength and resistance to decay by fungi attack were too determined. Results showed that using USV and density, curing occurs within 8 days. Moisture absorption ranges15 and 22% and decreases with decreasing of the amount of particles. MOR ranged from 0.40 a 1.23 MPa and the blocks with unwashed wooden particles and with CaCO3 addition had the greatest significant differences. In abrasion strength, blocks with unwashed wooden particles reported the best results. Finally, it was concluded that mixture with proportion of 60:40 (concrete:wood) and CaCO3 had the best performance and were not attacked by fungi decay.

Studies related to biomass production, with a focus on energy uses for short-rotation woody crops (SRWCs), are limited in Latin America. The research that is available relates to a variety of tested SRWC species (50 species), however, the most important species are Populus, Salix, Eucalyptus, Acacia, and Gmelina arborea. In the existing studies, stocking densities varied from 1111 to 20,000 trees per hectare, with square or rectangular spacing. One important advantage of SRWC systems in this region, compared to most regions worldwide, is the predictability of biomass yields due to the tropical climate conditions of the majority of the Latin American countries. Rotations of three and four years can be projected to produce total biomass yields of 30⁻50 tons/ha, with increments of 10⁻20 tons/ha/yr. Fertilization is performed in SRWC with the aim of preventing soil degradation and maintaining further production. In regards to possible uses of biofuel generated from SRWC in Latin America, an inconvenience is that there are neither well-established harvesting systems nor conventional pre-treatments to process the biomass. Processes that are available in the region that use biomass from SRWC for energy production are gasification and pellet production. Other potential biofuel processes, such as torrefaction and biochemical conversion, are limited in this area.

The main objective of this research was to evaluate the use of unmanned aerial vehicles (UAVs) in estimating the aboveground biomass and carbon, and the dasometric characteristics at three different spacings (2.5 m × 1.0 m, 2.5 m × 2.0 m and 2.5 m × 3.0 m) in a silvopastoral system (SPS) for the biomass production of Tectona grandis. A total of 90 trees were sampled, 63 of which were used to perform a dasometric evaluation (vertical and horizontal) in a spacing test in an SPS, and the rest to evaluate the use of UAVs in estimating the aboveground biomass in the spacing test. The results showed significant differences in average diameter at breast height (dbh) between spacings, and in aboveground biomass per tree. The amount of aboveground biomass and carbon per hectare increases at smaller spacings, but the differences were not statistically significant. A logarithmic model was prepared to estimate the dbh based on the crown diameter from the data collected taken in the field, since estimating this variable by means of UAVs is difficult. Significant differences were found in the aboveground biomass estimated using the field data compared to UAV data. The estimation of the crown diameter of the selected trees, hindered by the canopy closure in the SPS, was not adequate, which could influence the amount of aboveground biomass estimated using UAV data.

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 .

Las curvas laminadas fabricadas con chapas vaporizadas permiten obtener radios de curvatura más pequeños que cuando no se aplica este proceso. En este estudio, se presentan el comportamiento de madera de Alnus acuminata, Tectona grandis, Gmelina arborea, Terminalia oblonga, Alnus acuminata y Swietenia macrophylla provenientes de plantaciones de rápido crecimiento en la fabricación de curvaturas con radios de (4, 6, 8, 10, 12 y 14) cm. Fue posible obtener radios de curvaturas de 4 cm, a excepción de T. grandis de donde solo fue posible obtener radio de 6 cm. El proceso de vaporizado aumentó el contenido de humedad de la chapa en un rango de 3.3% a 10.2%. El adhesivo permite que el radio de la curva fabricada se mantenga en radios menores a 10 cm y en radios de 12 cm y 14 cm la curva tiende a abrirse (máximo 1%), para todas las especies, no obstante, la abertura se estabiliza al día 4 luego de fabricada. Las delaminaciones de las chapas se producen principalmente en los radios de 4 cm a 8 cm y se presentan con mayor incidente en la T. grandis y T. oblonga. La resistencia en cizallamiento de 7,5 MPa-11,2 MPa y no se alteró al someter a pruebas de envejecimiento, pero hay una mayor delaminación en todas las especies.

Modifications to a pellet manufacturing process must be made based on the characteristics of raw material used. The purpose of this work was to determine the alternations required to a wood pellet manufacturing process and the quality of the pellets produced using this process from five energy crops. Quality measurements include: the caloric value, the loss of moisture content in each production stage, the efficiency index of particle-pellet, ash content and quality as defined using the quantity of cracks and the transversal density and longitudinal density determined using X-ray radiography. The crops analyzed were rhizomatous plants, with caloric values ranging between 17.1 and 20.3 MJ kg −1 . This work determined that it was possible to produce pellets with Gynerium sagittatum and Phyllostachys aurea using the same production process for wood; however, Arundo donax and Pennisetum purpureum needed pre-air-drying and the Sorghum bicolor required mechanical dewatering before drying. A. donax , P. purpureum and G. sagittatum provided the highest efficiency index. When evaluating the pellet quality P. aurea and G. sagittatum hard a large quantity of cracks, unlike A. donax , P. purpureum and S. bicolor . The transversal and longitudinal pellet density varied from 1129 to 1294 kg m −3 . The highest values of bulk density were obtained in A. donax and P. purpureum , followed by G. sagittatum and P. aurea , and the lowest bulk density was obtained in S. bicolor . Althogh out, some species produced cracks and high ash content, this work demonstrated that it is possible to produce pellets with moderate quality.

Resumen En un proceso de gasificación la geometría de la biomasa es un factor necesario que considerar. El tamaño, forma y densidad de las partículas del biocombustible influyen en el transporte de las especies del sistema de reacción, velocidades de secado y descomposición térmica; los cuales son factores relacionados al desempeño general del proceso. Este trabajo evaluó las diferencias significativas que existen en el rendimiento y eficiencia del sistema de generación de energía eléctrica y térmica por la incidencia de dos geometrías en la biomasa de alimentación (pellets y astillas de madera), en el desempeño de un gasificador tipo “downdraft”. El perfil de temperatura de la zona de pirólisis fue en promedio (147 ± 15) °C mayor al utilizar astillas como alimentación en comparación con el uso de pellets. La caída de presión dentro del reactor fue menor en promedio, así como su variabilidad en el sistema, al utilizar astillas como alimentación; esto a pesar de que el poder calorífico del gas de síntesis obtenido fue levemente mayor para pellets (8,00 MJ/Nm3) que con respecto al obtenido con astillas (6,18 MJ/Nm3). Se obtuvo una Eficiencia de Gas Frío, así como la Eficiencia Térmica Global mayor al utilizar astillas de madera. La capacidad de aprovechamiento de la energía del syngas para producir potencia eléctrica, medido como la Eficiencia del Motor/Generador, estuvo dentro de los valores típicos para este sistema de conversión, y fue de (21,41 ± 3,23) % para astillas y (18,94 ± 3,68) % para pellets. Se obtuvo 564,50 kWh/t de rendimiento de proceso en términos eléctricos al emplear astillas, el cual fue mayor que al utilizar pellets (487,35 kWh/t), esto a una potencia de 6,2 kW. Con respecto al rendimiento de producción de gas de síntesis, con pellets fue menor con respecto a las astillas de madera (i.e. en promedio se produjo 1,75 kg de gas de síntesis por kilogramo de astillas, lo que significa un 25 % más que con pellets de madera). En conclusión, a pesar de que el manejo de astillas de maderas requiere ciertos cuidados para evitar el atascamiento dentro del sistema de conversión “downdraft” para producir gas combustible, en general las ventajas en proceso y eficiencias son mayores al utilizar madera en forma de astillas en comparación con pellets. Abstract The size, geometry, density and mechanical properties of the biofuel particles are important factors in the performance of any biomass gasification process. They influence the mass transfer rates of the reacting species just as the drying and the thermal decomposition rates in the rest of the system. This work evaluates the significant differences between two different feedstocks, wood pellets and woodchips, on the performance and efficiency of a pilot scale “downdraft” gasifier unit with a combined heat and power system. When using woodchips as feedstock, on average, the temperature profile of the pyrolysis zone was 147 ± 15 °C higher, while the pressure drop inside the reactor and its variability were lower. The Cold Gas Efficiency and Global Thermal Efficiency of the system were higher as well with the woodchips as feedstock, despite the fact that the calorific value of the synthesis gas produced from the wood pellets was 8.00 MJ/Nm3 and the one obtained from the woodchips was slightly lower at 6.18 MJ/Nm3. At a power generation of 6.2 kW, the syngas and electrical energy yields, were also higher on average for the woodchips at 1.75 kg/kg and 564.50 kWh/t, compared to the wood pellets as feedstock at 1.40 kg/kg and 487.35 kWh/t respectively. The relationship between the electrical energy yield and the calorific value of the syngas flow was stablished by means of the Motor/Generator Efficiency, and it was within typical range for this type conversion systems, at 21.41 ± 3.23 % for the woodchips and 18.94 ± 3.68 % for wood pellets. In conclusion, even though the transport of the woodchips within system is more prone to clogging, the higher efficiency and better overall process performance obtained when using woodchips, makes it the preferred feedstock for the system compared to the wood pellets.