Browsing by Author "Matos, M.A.A."
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- CO2 fluxes in short rotation coppices for energy productionPublication . Feliciano, Manuel; Tarelho, Luís A.C.; Matos, M.A.A.; Azevedo, JoãoShort rotation coppices (SRC), which usually consist of densely planted and high-yielding willow and poplar clones, can provide a sustainable source of energy. Furthermore, the potential of these systems as carbon sinks, recognized in the international debate on the global carbon balance and climate change impacts, may also make them a good option for many countries to receive ‘carbon credits’ to offset the effects of greenhouse gases emissions. As part of a research project and with the purpose of evaluating and optimizing the contribution of this type of intensively managed crop in carbon sequestration, CO2 vertical fluxes have been measured in a SRC stand installed in Bragança, Portugal. Chamber based-techniques were designed to measure both CO2 soil effluxes and exchange rates between the crop canopy and the atmospheric boundary layer. Soil fluxes are measured at various locations by means of an open top dynamic chamber. Biosphere/atmosphere CO2 exchange rates are evaluated by using a large ventilated open top chamber. CO2 analyses are performed by using an ADC 2250 differential infrared gas analyzer coupled to an automatic sampling and acquisition system. Measurements are taken every 10 seconds and averaged over half hour intervals. These measurements will be continued throughout several seasons, with the purpose of investigating daily and seasonal patterns of net ecosystem CO2 exchange rate. To support our analysis, other relevant environmental variables as meteorological, soil temperature and soil humidity have also been monitored. The results obtained so far are still scarce, but very encouraging since they show the ability of the system to perform reliable and continuous measurements of CO2 fluxes. This presentation will focus on the methodologies and on the evaluation of the magnitude of these production systems as carbon pools, in order to contribute to a better description of the current carbon fluxes pools.
- CO2 fluxes in short rotation coppices for energy productionPublication . Feliciano, Manuel; Tarelho, Luís A.C.; Matos, M.A.A.; Azevedo, JoãoShort rotation coppices (SRC), which usually consist of densely planted and high-yielding willow and poplar clones, can provide a sustainable source of energy. Furthermore, the potential of these systems as carbon sinks, recognized in the international debate on the global carbon balance and climate change impacts, may also make them a good option for many countries to receive ‘carbon credits’ to offset the effects of greenhouse gases emissions. With the purpose of evaluating and optimizing the contribution of this type of intensively managed crops in carbon sequestration, CO2 vertical fluxes have been measured in a SRC stand installed in Bragança, Portugal. Chamber based-techniques were designed to measure both CO2 soil effluxes and exchange rates between the crops canopy and the atmospheric boundary layer. Soil fluxes are measured at various locations by means of an open top dynamic chamber. Biosphere/atmosphere CO2 exchange rates are evaluated by using a large ventilated open top chamber. CO2 analyses are performed by using an ADC 2250 differential infrared gas analyzer coupled to an automatic gas sampling and data acquisition system. Measurements are taken every 10 seconds and averaged over half hour intervals. These measurements will be continued throughout several seasons, with the purpose of investigating daily and seasonal patterns of net ecosystem CO2 exchange rate. To support our analysis, other relevant environmental variables as meteorological, soil temperature and soil humidity have also been monitored. The results obtained so far are still scarce, but very encouraging since they show the ability of the system to perform reliable and continuous measurements of CO2 fluxes. This presentation will focus on the description of the developed experimental facility on the methodologies used and on the evaluation of the magnitude of the SRC systems as carbon pools.
- Fluxos verticais de CO2 em várias fases do ciclo de crescimento de uma cultura de curta rotação de choupo no Nordeste de PortugalPublication . Feliciano, Manuel; Azevedo, João; Tarelho, Luís A.C.; Matos, M.A.A.As culturas energéticas lenhosas de curta rotação constituem uma oportunidade para aumentar a rentabilidade de muitos ecossistemas, principalmente nas regiões onde podem representar uma mais-valia comparativamente às culturas alimentares. Estas culturas são também consideradas um meio eficaz de mitigação do efeito estufa, devido à sua contribuição para a redução do uso de combustíveis fósseis e ao seu impacto positivo na transferência do carbono da atmosfera para o sistema solo/vegetação (Schulze et al. 2000). Com o objetivo de avaliar e otimizar a contribuição deste tipo de culturas de gestão intensiva no sequestro de carbono, procedeu-se à medição de fluxos verticais de CO2 num sistema de biomassa lenhosa para produção de energia, instalado no nordeste transmontano, em particular numa plantação de choupo híbrido.
- Local-scale fluxes of carbon dioxide in a poplar short rotation coppicePublication . Feliciano, Manuel; Tarelho, Luís A.C.; Matos, M.A.A.; Ribeiro, A.C.; Azevedo, JoãoShort rotation crops can provide biomass fuel for a wide range of users in co-firing plants and to replace other conventional energy resources used for heating and/or power generation. These biomass systems have also a considerable potential for carbon sequestration, which may constitute a good option to offset greenhouse gas emissions. With the purpose of evaluating the contribution of these intensively managed crop systems to carbon sequestration, we measured daily and seasonal patterns of net exchange rates of CO2 and soil effluxes in a poplar short rotation plot installed in the vicinity of the city of Bragança, Portugal. Open top chamber based-techniques were designed to measure both CO2 soil effluxes and exchange rates between the crop canopy and the atmosphere. Chambers inflow and outflow CO2 concentrations were measured by means of an ADC 2250 differential infrared gas analyzer coupled to an automatic sampling and acquisition system. This study started in the summer of 2010 and the data collected so far covers only part of the annual growth cycle of the poplar coppice. Poplar trees were already in an advanced stage of their growth cycle and from then on they have been subjected to stress environmental conditions, especially heat and high soil moisture deficit, which were observed until the end of September. The main results showed a significant variation of CO2 fluxes over the evaluation period. Day/night variation pattern was a common characteristic, but with shapes and magnitudes clearly influenced by the physiological activity of the poplar trees. The pronounced diurnal cycle with CO2 uptake during daytime and an upward flux at night registered in late September gave gradually rise to a CO2 emission pattern in the second half of November, slightly before the falling of the leaves. These preliminary results showed the potential of this energy crops to absorb large amounts of carbon dioxide during the growing season, but in the senescent period and/or under very stressful environmental conditions these biomass systems become predominantly a source of CO2.
- Wood combustion in a domestic stove: characterization of operating conditions and ashes producedPublication . Tarelho, Luís A.C.; Neves, D.S.F.; Lopes, M.H.S.D.; Teixeira, Eva Raquel Frutuoso; Matos, M.A.A.; Freire, M.S.M.; Azevedo, JoãoWood combustion in stoves for domestic heating purposes is a common practice in Portugal. However, some environmental impacts related to this practice are recognized, such as its effects on both indoor and outdoor air quality, and also those related to the management of the ashes produced. Results from an investigation about combustion of three wood varieties commonly used in Portugal in a batch-operated domestic stove are presented in this work. The wood fuels, the stove and the laboratorial facility developed to accomplish the measurements are described. Also, results from the continuous monitoring of the mass of the fuel batches undergoing combustion, the flow rate of the combustion air, the temperature in the combustion chamber and along the chimney, and the composition of the exit flue gas (O2, CO2, CO, total hydrocarbons) are presented. Ashes were collected from the grate of the stove after the combustion cycles and were characterised in regard to particle size distribution, chemical composition, mineralogy and leaching behaviour. The results from this investigation permit a better understanding about wood combustion and ashes produced in domestic stoves, which is needed for improving the performance of this type of equipments.