Browsing by Author "Viana, Helder Filipe dos Santos"
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- Assessment of Forest Aboveground Biomass Stocks and Dynamics with Inventory Data, Remotely Sensed Imagery and GeostatisticsPublication . Viana, Helder Filipe dos Santos
- A Biomassa Verde e Lenhosa dos Espaços Urbanos como Fonte Energética para os Edifícios Públicos da Cidade de ViseuPublication . Viana, Helder Filipe dos Santos; Pinto, Nuno; Costa, Daniela; Barracosa, PauloA biomassa gerada pelos espaços verdes urbanos constitui uma fonte de resíduos significativa que, muitas vezes, é direccionada directamente para aterros podendo ser aproveitada para fins energéticos, nomeadamente no aquecimento térmico de alguns edifícios públicos. O presente trabalho apresenta a quantificação da biomassa verde indiferenciada gerada pelos espaços verdes urbanos, depositada nos pontos de recolha específicos, e da biomassa lenhosa proveniente das podas realizadas nas árvores existentes na cidade de Viseu. Simultaneamente, estimam-se as necessidades energéticas (eléctricas e térmicas), no Verão e Inverno, dos principais edifícios públicos da cidade. A quantificação dos resíduos produzidos anualmente foi avaliada por inquéritos às empresas responsáveis pelas podas das árvores da cidade, à autarquia e ao centro de tratamento dos resíduos sólidos urbanos, para o período de 2004 a 2007. Fez-se também a estimativa a partir da caracterização dendrométrica do parque arbóreo existente, a qual serviu para comparar e validar os resultados obtidos. As necessidades energéticas médias anuais foram estimadas a partir do inquérito realizado, no período entre 2004 e 2006, em 49 edifícios públicos como escolas, unidades de saúde, edifícios da autarquia, entre outros. Os resultados mostram que as necessidades térmicas médias anuais dos edifícios estudados rondam os 109.245,78 GJ. A biomassa produzida ronda as 106,5 t/ano de resíduos lenhosos e 103,3 t/ano de resíduos verdes, os quais foram convertidos em valores de energia. A biomassa unicamente lenhosa poderia suprir cerca de 10,3% das necessidades térmicas de Inverno, das 19 escolas levantadas nestes estudo. Dado que muita da biomassa produzida na cidade não é contabilizada, uma vez que é depositada juntamente com os resíduos sólidos urbanos, o potencial energético destes resíduos poderia ser muito superior.
- Life cycle assessment of residual forestry biomass chips at a power plant: a Portuguese case studyPublication . Ferreira, José; Viana, Helder Filipe dos Santos; Esteves, Bruno; Cruz-Lopes, Luísa; Domingos, IdalinaThe residual forest biomass (RFB) sector has been experiencing strong development at European level and particularly in Portugal mainly due to the increase of energy production from renewable sources. The aim of this study is to assess the environmental impacts of eucalyptus RFB chips production chain in Portugal. The environmental and economic impact comparison of the processes included in the production chain is presented as well. The environmental impacts were calculated by the life cycle assessment approach described in the ISO 14040 series of standards. The production chain assessed included all processes from eucalyptus forest until the delivery of RFB chips at the power plant. The main conclusion of this study is that eucalyptus wood production is the process that presents the greatest environmental impact through the product life cycle.
- Modelling aboveground NPP of Portuguese forest, at regional scale, using field inventory data and NDVI from Landsat 5 tm, Modis and Spot Vegetation ImageryPublication . Viana, Helder Filipe dos Santos; Lopes, Domingos; Aranha, JoséEstimates of aboveground net primary production (ANPP) have been used to address a broad range of questions, from forage availability for livestock to estimates of the global carbon balance. Considering the importance of ANPP as an ecological variable and additionally the complexity of its measurement, the objective of this paper was to develop and test a procedure of simple implementation, in order to estimate the ANPP, at regional scale. The ANPP was estimated as a function of some stand structural variables and by integrating the normalized difference vegetation index (NDVI) derived from Landsat TM (30m), MODIS (250m) and SPOT vegetation imagery (1Km). A total of 150 plots were sampled, using the destructive method, within Pinus pinaster (maritime pine) and Eucalyptus globulus (eucalyptus) stands. Within all plots, all trees were measured (e.g. diameter at breast height, total height, dominant height, canopy height, canopy horizontal projection area, age) in order to calculate stands characteristics (e.g. basal area per hectare, number of trees per hectare). Within some plots, the average representing tree was cut and logged in order to weight coppice,branches and log and determine the total weight per hectare. The understory vegetation was measured (shrubs density, height and estimated age), using the line intersection method, and the weight per hectare was achieved. The total biomass was subsequently converted in ANPP (g.m-2 .year-1). After processing satellite imagery data, the NDVI values were derived, for each sampling plot. The NDVI values and the measured vegetation variables were used for adjustment of regression models, having ANPP as dependent variable. The results obtained were satisfactory, and demonstrate the utility of using the spectral response patterns of vegetation to estimate the ANPP. The best ANPP estimates were achieved for Pinus pinaster stands with shrubs in underwood, using the NDVI as independent variable, individually or combined with the vegetation variables, derived from Landsat 5 TM imagery (R2 aj = 0.52; RMSE = 23%), MODIS imagery (R2 aj = 0.60; RMSE = 21%) and SPOT Vegetation VGT imagery (R2 aj = 0.54; RMSE = 23%).
- Particleboard Production from Paulownia tomentosa (Thunb.) Steud. Grown in PortugalPublication . Esteves, Bruno; Aires, Pedro; Sen, Umut; Gomes, Maria da Glória; Guiné, Raquel P. F.; Domingos, Idalina; Ferreira, José; Viana, Helder Filipe dos Santos; Lopes, Luísa P. CruzPaulownia wood has raised high attention due to its rapid growth and fire resistance. The number of plantations in Portugal has been growing, and new exploitation methods are needed. This study intends to determine the properties of particleboards made with very young Paulownia trees from Portuguese plantations. Single layer particleboards were produced with 3-year-old Paulownia trees using different processing parameters and different board composition in order to determine the best properties for use in dry environments. The standard particleboard was produced at 180 °C and a 36.3 kg/cm2 pressure for 6 min using 40 g of raw material with 10% urea-formaldehyde resin. Higher particle size lead to lower-density particleboards, while higher resin contents lead to higher density of the boards. Density has a major effect on board properties with higher densities improving mechanical properties such as bending strength, modulus of elasticity (MOE) and internal bond, lower water absorption but higher thickness swelling and thermal conductivity. Particleboards meeting the requirements for dry environment according to NP EN 312 standard, could be produced with young Paulownia wood with acceptable mechanical and thermal conductivity properties with density around 0.65 g/cm3 and a thermal conductivity of 0.115 W/mK.
- Particleboard Production from Paulownia tomentosa (Thunb.) Steud. Grown in Portugal.Publication . Esteves, Bruno; Aires, Pedro; Sen, U; Gomes, Maria da Glória; Guiné, Raquel; Domingos, Idalina; Ferreira, José; Viana, Helder Filipe dos Santos; Lopes, Luísa P. Cruz
- Termite resistance, chemical and mechanical characterization of paulownia tomentosa wood before and after heat treatmentPublication . Esteves, Bruno; Ferreira, Helena; Viana, Helder Filipe dos Santos; Ferreira, José; Domingos, Idalina; Cruz-Lopes, Luísa; Jones, D.; Nunes, L.The introduction of new species in forest management must be undertaken with a degree of care, to help prevent the spread of invasive species. However, new species with higher profitability are needed to increase forest products value and the resilience of rural populations. Paulownia tomentosa has an extremely fast growth. The objective and novelty of this work was to study the potential use of young Paulownia trees grown in Portugal by using heat treatment to improve its properties, thereby allowing higher value applications of the wood. The average chemical composition of untreated and heat-treated wood was determined. The extractive content was determined by successive Soxhlet extraction with dichloromethane (DCM), ethanol and water as solvents. The composition of lipophilic extracts was performed by injection in GC-MS with mass detection. Insoluble and soluble lignin, holocellulose and α-cellulose were also determined. Physical (density and water absorption and dimensional stability) and mechanical properties (bending strength and bending stiffness) and termite resistance was also determined. Results showed that extractive content increased in all solvents, lignin and α-cellulose also increased and hemicelluloses decreased. Compounds derived from the thermal degradation of lignin were found in heat-treated wood extractions. Dimensional stability improved but there was a decrease in mechanical properties. Resistance against termites was better for untreated wood than for heat-treated wood, possibly due to the thermal degradation of some toxic extractives.
- The Influence of Age on the Wood Properties of Paulownia tomentosa (Thunb.) Steud.Publication . Esteves, Bruno; Cruz-Lopes, Luísa; Viana, Helder Filipe dos Santos; Ferreira, José; Domingos, Idalina; Nunes, Leonel J. R.Forests in Portugal are highly dependent on a short number of wood species, and new species with higher profitability are needed. The Paulownia species has generated great interest due to its fast-growing and relatively good wood properties. However, environmental factors have shown that Paulownia grows differently in each case. This study intends to determine the properties of young Paulownia trees from Portuguese plantations to determine the best age to cut the trees according to their use. The chemical composition (extractives in dichloromethane, ethanol and water, lignin, α-cellulose, and hemicelluloses), heating value, elemental analysis (CHNO), inorganic elements and thermogravimetric analyses (TGA), and the most important mechanical and physical properties (density, MOE, bending strength, water absorption equilibrium, moisture content, and dimensional changes) were determined for 1-, 3-, and 5-year-old trees. The results show that, chemically, the extractives increased while hemicelluloses decreased with age, and no trend was found for lignin and α-cellulose. The physical and mechanical properties increased with age, except for the MOE and bending strength. The 5-year-old samples presented the best features for pellet production, namely, calorific power, elemental composition CHNO and sulfur, and inorganic elements.