• Energy Research

The building envelope is critical to reducing operational energy in residential buildings. Under moderate climates, as in South-Western Europe (Portugal), thermal operational energy may be substantially reduced with an adequate building envelope selection at the design stage; therefore, it is crucial to assess the trade-offs between operational and embodied impacts. In this work, the environmental influence of building envelope construction with varying thermal performance were assessed for a South-Western European house under two operational patterns using life-cycle assessment (LCA) methodology. Five insulation thickness levels (0–12 cm), four total ventilation levels (0.3–1.2 ac/h), three exterior wall alternatives (double brick, concrete, and wood walls), and six insulation materials were studied. Insulation thickness tipping-points were identified for alternative operational patterns and wall envelopes, considering six environmental impact categories. Life-cycle results show that, under a South-Western European climate, the embodied impacts represent twice the operational impact of a new Portuguese house. Insulation played an important role. However, increasing it beyond the tipping-point is counterproductive. Lowering ventilation levels and adopting wood walls reduced the house life-cycle impacts. Cork was the insulation material with the lowest impact. Thus, under a moderate climate, priority should be given to using LCA to select envelope solutions.

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.

This article presents a life-cycle assessment (LCA) of rapeseed produced in Central Europe (France, Germany and Poland), addressing different fertilization and management practices. Two alternative fertilization scenarios were compared (on the basis of the most common fertilizer types used in Europe, namely nitrogen, phosphate P2O5, and potash K2O fertilizers) and two different scenarios of soil management practices were assessed (taking into account climate and soil type prevalent in each region). Six environmental impact categories were investigated: abiotic depletion; global warming; acidification; eutrophication; ozone layer depletion; and photochemical oxidation. Results showed that the choice of fertilizer type had significant implications in the environmental impacts. Calcium ammonium nitrate (CAN) manufacturing had considerably higher greenhouse gas emissions than urea production, due to the use of nitric acid in the former. In terms of field emissions, ammonia and nitrate released following the application of nitrogen fertilizers dominated the acidification and eutrophication impacts. Nitrogen–phosphorus–potassium (NPK) compounds showed particularly high impacts in terms of photochemical oxidation, as a result of sulfur dioxide emissions from manufacturing. The remaining fertilizers (P2O5 and K2O) hardly contributed to the impacts. Soil carbon change associated with different agricultural management practices significantly contributed to the greenhouse gas (GHG) intensity of rapeseed production, but important soil carbon stock variations were calculated: between 938 (release) and 271 kg CO2eq/1000 kg dry seeds (sequestration) due to different standard soil organic carbon contents in the three rapeseed production systems and alternative tillage methods in the reference scenarios of land management.

Abstract Sunflower is an important feedstock for food and energy purposes in southern European countries. The main goal of this article is to present an environmental life-cycle assessment of sunflower cultivated in Portugal comparing irrigated and rainfed systems, incorporating parameter uncertainty and assessing alternative land use change scenarios. The functional unit adopted was 1 kg of sunflower seeds (hectare of land was also addressed in a sensitivity analysis). The average productivity (kg ha −1 year −1 ) of irrigated sunflower was 3.5 times higher than of rainfed. Irrigated sunflower presented higher acidification impact than rainfed. Similar greenhouse gas intensity and eutrophication impact were found for irrigated and rainfed systems taking into account the high variability and uncertainty levels calculated. Higher uncertainty levels were observed for the impacts of irrigated sunflower compared with rainfed, due to field emissions. Greenhouse gas intensity of sunflower greatly depends on land use change scenarios (the lowest emissions occur for the conversion of severely degraded grassland into irrigated sunflower and the highest emissions for the conversion of improved management grassland into rainfed sunflower). The sensitivity analysis performed for the functional unit showed very different impacts per hectare of land compared with those calculated per kg of sunflower seeds: the irrigated system had the highest impacts for all categories.

This article presents a methodology to classify light-duty vehicles according to their environmental impacts. The classification is based on Life-Cycle Impact Assessment indicators and vehicle operation indicators, which are aggregated using a Multi-Criteria Decision Analysis (MCDA) method. In contrast with most literature combining Life-Cycle Assessment (LCA) and MCDA, vehicles are not compared directly; they are compared to pre-established profiles defining a set of classes. These profiles are established relatively to the impacts of the country's light-duty fleet. The ELECTRE TRI method is chosen for MCDA classification, thus avoiding complete substitutability among criteria and allowing for imprecision in the data. MCDA typically incorporates the subjective values of decision makers, namely through criteria weighting. To obtain conclusions that are not contingent on a given weight vector, we consider a space of weight vectors defined by constraints with a clear rationale and obtain all the possible results compatible with those constraints. The methodology is applied to classify six vehicles available in Portugal with different powertrains: Gasoline and Diesel Internal Combustion Engine Vehicles, Plug-in Hybrid Electric Vehicles (10 and 40-mile battery range) and Battery Electric Vehicle. The discussion suggests how this methodology might be useful for a decision-making entity that wishes to classify vehicles according to their environmental impacts.

Renewable energy sources, and particularly biofuels, are being promoted as possible solutions to address global warming and the depletion of petroleum resources. Nevertheless, significant disagreement and controversies exist regarding the actual benefits of biofuels displacing fossil fuels, as shown by a large number of life-cycle studies that have varying and sometimes contradictory conclusions. This article presents a comprehensive review of life-cycle studies of biodiesel in Europe. Studies have been compared in terms of nonrenewable primary energy requirement and GHG intensity of biodiesel. Recently published studies negate the definite and deterministic advantages for biodiesel presented in former studies. A high variability of results, particularly for biodiesel GHG intensity, with emissions ranging from 15 to 170 gCO2eq MJf−1 has been observed. A detailed assessment of relevant aspects, including major assumptions, modeling choices and results, has been performed. The main causes for this high variability have been investigated, with emphasis on modeling choices. Key issues found are treatment of co-product and land use modeling, including high uncertainty associated with N2O and carbon emissions from cultivated soil. Furthermore, a direct correlation between how soil emissions were modeled and increasing values for calculated GHG emission has been found. A robust biodiesel life-cycle modeling has been implemented and the main sources of uncertainty have been investigated to show how uncertainty can be addressed to improve the transparency and reliability of results. Recommendations for further research work concerning the improvement of biofuel life cycle modeling are also presented.

This article assesses marginal greenhouse gas (GHG) emissions of electricity generation in Portugal to understand the impact of activities that affect electricity demand in the near term. In particular, it investigates the introduction of electric vehicles (EVs) in the Portuguese light-duty fleet considering different displacement and charging scenarios (vehicle technologies displaced, EV charging time). Coal and natural gas were identified as the marginal sources, but their contribution to the margin depended on the hour of the day, time of year, and system load, causing marginal emissions from electricity to vary significantly. Results show that for an electricity system with a high share of non-dispatchable renewable power, such as the Portuguese system, marginal emissions are considerably higher than average emissions. Because of the temporal variability in the marginal electricity supply, the time of charging may have a major influence on the GHG emissions of EVs. Off-peak charging leads to higher GHG emissions than peak charging, due to a higher contribution of coal to the margin. Furthermore, compared to an all-conventional fleet, EV introduction causes an increase in overall GHG emissions in most cases. However, EV effects are very dependent on the time of charging and the assumptions about the displaced technology.