• Energy Research

Abstract Ash generated during the combustion of woody biomass for energy production is an industrial waste that should be properly managed in order to minimise the respective environmental impacts. Woody biomass ash valorisation in construction materials to replace conventional materials is an alternative that has proven to be technically feasible. On the other hand, it can present potential environmental impacts that should be evaluated to support the choice of more sustainable alternatives. Thus, the purpose of this work is to assess the potential impacts of woody biomass ash valorisation of through incorporation in construction materials using life cycle assessment. The valorisation alternatives consider the incorporation of woody biomass ash in cement mortars, adhesive mortars, concrete blocks, and bituminous asphalts. In addition, a base scenario consisting of ash landfilling is also assessed. Four types of woody biomass ashes were considered, namely fly and bottom ashes generated in a vibrating grate and fly and bottom ashes generated in a fluidised bed. The impact assessment method used is that suggested in the International Reference Life Cycle Data System for selected impact categories. The results showed that the impacts of ash transport and pre-processing and the impacts of producing the avoided materials are factors that affect the net impact of the valorisation scenarios and should be considered in the end-of-life management of biomass ash. Nevertheless, all valorisation scenarios had a lower impact than landfilling in all the impact categories under study, resulting in a significant decrease of the environmental impacts in some scenarios.

Abstract This paper compares the water footprint profiles of four feedstocks used for biodiesel production: palm, soya, rapeseed and waste cooking oil (WCO). The profiles include: (a) a water scarcity footprint related to freshwater consumption impacts and (b) a water quality degradation footprint related to freshwater degradation impacts. The water scarcity footprint was assessed using two impact assessment methods: one based on water stress indices (WSIs) and the other on the available water remaining (AWARE) indicator. The water degradation footprint was assessed considering the environmental mechanisms covered by the impact categories of eutrophication, aquatic acidification, human toxicity and freshwater ecotoxicity. The water scarcity profiles ranged from 0.002 to 2.11 world m3eq kg−1 oil (WSI method) and from 0.008 to 133.57 world m3eq kg−1 oil (AWARE method). Both methods showed that the cultivation stage assumes the primary role in the water scarcity footprint results and identified the same systems with higher water scarcity footprints. However, for the oil systems with closer results, the rank order given by each method is different due to the characterization factors of each method. Nevertheless, the results obtained with the AWARE method give more comprehensive water scarcity footprint results than those obtained when applying WSIs because AWARE considers the aquatic ecosystem water demand. The water degradation footprint of virgin oils is mainly caused by fertilizers and pesticides used in cultivation. WCO systems present lower impacts for all impact categories with the exception of human toxicity-cancer. The choice of locations with lower water scarcity to produce oil crops can be a determinant in the calculation of lower impacts. Moreover, optimizing fertilization schemes or choosing climatic conditions that require less fertilizers, pesticides and water consumption can reduce the impacts of the water footprint profile of vegetable oils.

Abstract The ornamental earthenware ceramic manufacturing is typically a multifunctional system because several pieces with different dimensions and geometries are produced in the same mill, at the same time. Therefore, an allocation procedure is needed in order to quantify the share that each ornamental earthenware ceramic piece represents in the manufacturing total energy consumption and costs and greenhouse gas (GHG) emissions. The main aim of this study was to present a methodology to allocate to each piece the energy consumed in the ornamental earthenware ceramic manufacturing process. The methodology relies on mass, volume or number of pieces, depending on the type of energy and stage of manufacturing, and has been tested and validated in a real manufacturing context at an ornamental earthenware ceramic mill. Another objective of this study was the determination of the energy consumption and cost and the GHG emissions, per piece, of some pieces produced in the mill where the allocation methodology was applied, in order to identify improvement opportunities in the manufacturing process. The results show that the energy consumption and costs and the GHG emissions of the studied ceramic pieces are strongly dependent on its dimension, both in terms of mass and volume, and also on the piece susceptibility to crack and to experience deformations and imperfections. These results suggested some improvement measures to reduce the consumption of electricity, natural gas (in shaping and in the biscuit and glost firing cycles) and calcite used as raw material.

Recently, wood pellets have become a reliable and clean renewable fuel for residential heating, replacing fossil fuels and reducing greenhouse gas emissions. Wood pellets are normally produced in industrial pellet plants (centralised production), but decentralised small-scale local production also occurs. This study applies Life Cycle Assessment (LCA) to quantify and compare the environmental profile of one centralised and two decentralised alternatives for wood pellet production for residential heating in Portugal: (1) industrial wood pellets production (centralised), (2) wood pellets production at sawmills (decentralised) and (3) wood pellets production at households (decentralised). System boundaries include the stages of forest management, wood pellet production, wood pellet distribution and wood pellet energetic conversion. The impact results show that industrial pellet production ranks as the worst alternative, while pellet production at households has the best environmental profile for all the impact categories under study. However, the environmental impacts of pellet production at the sawmill do not differ greatly from those of the pellet production at households; they are 14 to 16% higher for global warming and fossil resources scarcity and 0.3 to 3% higher for the remaining impact categories. The worst environmental performance of the industrial pellet production alternative is mainly due to high electricity and diesel consumption during wood pellet production and the use of logging residues to generate heat for drying biomass feedstock. A sensitivity analysis was performed to evaluate the influence of changing the distance travelled during the transport of packed pellets to stores and sawdust to households. The results show changes in the environmental performance ranking, highlighting that for short distances, both decentralised alternatives can be more sustainable from an environmental perspective than the centralised alternative, but for larger distances, the pellet production at households should be avoided.

Abstract The Portuguese government's new strategy is based on the predicted increase in the country's installed electricity capacity through the use of biomass residues, including forest biomass residues. However, this strategy implies that the use of forest biomass residues in electricity production will most likely be at the expense of alternative uses, such as heat and biofuel production. Therefore, what is the best use of forest biomass residues available in the country from an environmental perspective? To answer this question, in this study, a consequential life cycle assessment was applied to assess three different scenarios: 1) the production of electricity in dedicated power plants; 2) the cogeneration of electricity and heat in combined heat and power plants; and 3) the production of bioethanol by biochemical conversion. The results showed that the strategy of using forest biomass residues for electricity production would be advantageous in relation to the baseline (i.e. leaving forest residues in forest soil and using fossil fuel sources to produce energy) only in some environmental impact categories. The results showed that the cogeneration of electricity and heat production was the best alternative among the three scenarios. However, regarding the effects related to particulate matter and marine eutrophication, the results showed that this alternative would perform better than baseline if the displaced fuels were coal in electricity production and at least 12% fuel oil (and the rest natural gas) in heat production. The conversion of forest biomass residues to bioethanol was the least beneficial regarding all categories under study.

Moving towards a global bioeconomy can mitigate climate change and the depletion of fossil fuels. Within this context, this work applies a set of multi-criteria decision analysis (MCDA) tools to prioritise the selection of five alternative bioenergy systems for residential heating based on the combination of three commercial technologies (pellet, wood stove and traditional fireplace) and two different feedstocks (eucalypt and maritime pine species). Several combinations of MCDA methods and weighting approaches were compared to assess how much results can differ. Eight indicators were used for a sustainability assessment of the alternatives while four MCDA methods were applied for the prioritisation: Weighted Sum Method (WSM), Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS), Elimination and Choice Expressing Reality (ELECTRE), and Preference Ranking Organization Method for Enrichment Evaluation (PROMETHEE). Regarding the sustainability performance indicators, the highest environmental impacts were calculated for the fireplace alternatives, and there was not a best environmental option. Also, no clear trend was found for the economic and social dimensions. The application of MCDA tools shows that wood stove alternatives have the best sustainability performance, in particular wood stove with combustion of maritime pine logs (highest scores in the ranking). Regarding the worst alternative, fireplaces with combustion of eucalypt logs ranked last in all MCDA rankings. Finally, a sensitivity analysis for the weighting of the performance indicators confirmed wood stoves with combustion of maritime pine logs as the leading alternative and the key role of the analysts within this type of MCDA studies.

Abstract The automobile industry is demanding new car components to reduce vehicle emissions and increase efficiency. Lightweighting strategies are the most followed by manufacturers to reduce the weight and fuel consumption of vehicles. In this study, an innovative signal cable solution for the wire harnesses of vehicle is analysed through a life cycle assessment (LCA) and benchmarked with the replaced cable. The innovative cable is made up of a copper-tin alloy, while the traditional cable is made of copper. Both products are twisted and insulated with plasticised polyvinyl chloride. The new cable reduces the weight and volume by 53% and 41%, respectively, compared to the traditional cable. The production of raw and ancillary materials was found to be the main impact contributor, mainly due to the production of the conductive and insulation materials. Similarly, electricity consumption was the main impact carrier for the manufacturing stage. The environmental burdens obtained for the innovative cable were, on average, 54% lower than those obtained for the replaced one. Additionally, the potential marginal gains for the automobile industry were evaluated in terms of fuel consumption reduction, which is linked to vehicle weight, and the derived emissions, obtaining a significant exhaust emission reduction of 160 kg CO2 eq when compared to the baseline scenario. Finally, the LCA of these products was decisively influenced by the consumption of raw materials and, therefore, the reduction of the thickness of the wire makes the cables considerably more sustainable from an environmental point of view.

Biomass plays a fundamental role in numerous decarbonisation strategies that seek to mitigate the short- and long-term effects of climate change. Within this context, decision-makers’ choices need to comprehensively consider potential sustainability effects associated with bioenergy systems. In particular, due to the lack of studies addressing the social sustainability of bioelectricity, the present work applies the Social Life Cycle Assessment (S-LCA) methodology to compare the social performance of two biomass-to-electricity systems located in Portugal based on either fluidised-bed or grate furnace technology. S-LCA involves a comprehensive approach for holistic evaluation and data interpretation of social aspects. Six social indicators were benchmarked: child labour, forced labour, gender wage gap, women in the sectoral labour force, health expenditure, and contribution to economic development. The results show that the implementation of fluidised-bed furnaces as a more efficient conversion technology could reduce by 15–19% the selected negative social impacts, except women in the sectoral labour force. When enlarging the interpretation to a sustainability perspective, the general suitability of the fluidised-bed furnace system would be further emphasised under environmental aspects while jointly providing valuable insights for informed decision-making and sustainability reporting.