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- 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.
- Assessment of Forest Aboveground Biomass Stocks and Dynamics with Inventory Data, Remotely Sensed Imagery and GeostatisticsPublication . Viana, Helder Filipe dos Santos
- 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%).
- 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.