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Universidade de Tras os Montes E Alto Douro (2020)

Biomassa agroflorestal residual : quantificação e caracterização para fins energéticos

Enes, Teresa Raquel Duarte

Titre : Biomassa agroflorestal residual : quantificação e caracterização para fins energéticos

Auteur : Enes, Teresa Raquel Duarte

Université de soutenance : Universidade de Tras os Montes E Alto Douro

Grade : Doutoramento em Ciências Agronómicas e Florestais 2020

Résumé
Residual vegetal biomass (eg. material from pruning, tips and branches left from thinning) is currently a problem in Portugal. On the one hand, there is no destination for this waste, on the other hand their accumulation on rural land constitutes a permanent risk of wildfire. Due to Portugal’s dependence on fossil fuels and the large availability of vegetal biomass in the country, it is essential to promote the use of these wastes. Plant biomass is considered a waste when it has no use. However, if it becomes raw material for another activity, it becomes a by-product of agroforestry activity. The characterization, quantification and georeferencing of sites with the highest biomass accumulation will be an asset both at ecological and economic level, as this biomass can be used for energy purposes. In addition, the growing demand for plant biomass for energy production expected in the coming years in Portugal raises concerns about its availability and characterization. The general objectives proposed in this paper meet the deficiencies mentioned and concern the quantification and thermochemical characterization of biomass of shrub species in burnt areas, as well as agricultural and forest residues. Also taking into consideration the existence of a gap in the management knowledge of the natural regeneration of maritime pine, a new management support approach is also presented here, based on the maximum density trajectory attainable in the early stages of development of maritime pine. The proposed model provides ecologically based support for defining forestry guidelines for species management and can be a tool for managing the growth of this species in burnt areas and intrinsically the amount of biomass produced. To achieve the objectives, study plots were selected, mainly located in the North of Portugal, with some data collected in the Centre. The biomass quantification of the shrubs was made through the use of allometric equations, presenting new quantification models. The studies carried out allow us to conclude that in the study areas, the estimated amount of available biomass may meet the needs of the population. The thermochemical analyses consisted essentially in the evaluation of the Superior Calorific Power, the quantification of Macromolecules, namely extractives, lignin and holocellulose and, finally, in the analysis / evaluation of the chemical elements in each type of biomass. In general, the biomass of the shrub species showed the best characteristics for energy purposes, mainly through combustion processes.

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