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Browsing CIMA by advisor "Barreira, Luísa Paula Viola Afonso"
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- Production of biofuels from microalgal biomassPublication . Carvalho, Henrique Miguel Mata; Barreira, Luísa Paula Viola Afonso; Barros, Raúl J.With the increase in greenhouse gases (GHG) concentrations on the atmosphere, and the problems associated with it, the interest in the development of microalgae-derived biofuels has grown significantly in recent years. Microalgal biomass presents several advantages over feedstocks commonly used for the production of biofuels. However, current production costs are still too high and uncompetitive when compared to fossil fuels. In order to reduce the production costs of microalgal-based biofuels, the development of a biorefinery combining the production of different biofuels was previously proposed. In the present work, biodiesel was synthetized from the biomass of Botryococcus braunii, and the properties of the produced biodiesel were assessed according to the European and American specifications. The defatted biomass obtained as a co-product was further upgraded by anaerobic digestion into biogas, using different consortia of bacteria. The net energy and mass balance of the biofuels produced were made, to discuss the viability of microalgal-based biodiesel production coupled with the valorisation of the spent biomass under a biorefinery concept. B. braunii biomass had an lipid content of 14.8%, after the transesterification the yield was 46.8%, and the final biodiesel yield after purification was 30.5%. The predominant fatty acids present on the biodiesel were C16:0; C18:2n6 and C18:1. The biodiesel produced fulfilled the international specifications, except for the parameters density, viscosity and phosphorus content. The highest yields obtain on the anaerobic digestion were under mesophilic conditions (35°C). The digestion of the defatted biomass (without lipids, 369 mL biogas/g VS) performed similar or better results than the raw biomass (333 mL biogas/g VS). The defatted biomass reached a biogas methane content of 82% and 72% for 35°C and 25°C, respectively. The experimental results obtained at a laboratory scale were scaled up with a process simulation software (SuperPro Designer) to produce 1000 kg of biodiesel from 16.4 t of biomass, which will lead to a production of 2687 kg of methane, making an overall energy production of 48145 kWh. However, the energy spent on the process was 94341 kWh.