Abstract

Total nitrous oxide (N2 O) emissions from a conventional active sludge process were calculated using a mathematical emission model and dissolved N2 O in the water phase by a N2 O water sensor. Calculated emissions showed good agreement with measured emissions based on concentrations and airflow in the off-gas ventilation system from the covered process. Various tests for a wide range of potentially affecting parameters indicated robust and reliable emission estimations by the model. Thus, common uncertainties in input data would still provide good emission estimations. Measurements of dissolved N2 O required low maintenance and N2 O emission monitoring based on such measurements might therefore be considered as a significant practical improvement. This would be advantageous especially in non-enclosed wastewater treatment plants (WWTPs) otherwise requiring complex off-gas measurements. As the sensor is connected directly to the WWTPs monitoring and control system, emissions calculations could be incorporated.

Abstract

Road transport is responsible for a significant share of the global GHG emissions. In order to address the increasing trend of road vehicle emissions, due to its heavy reliance on oil, Nordic countries have set ambitious goals and policies for the reduction of road transport GHG emissions. Despite the fact that the latest developments in the passenger car segment are leading towards the progressive electrification of the fleet, the decarbonization of heavy-duty vehicle segment presents significant challenges that are yet to be overcome. This study focuses, on the first part, on the regulatory framework of fuel economy standards of road vehicles, highlighting the absence of a European regulation on fuel efficiency for the heavy-duty sector. Energy efficiency technologies can be grouped mainly in vehicle technologies, driveline and powertrain technologies, and alternative fuels. The fuel efficiency of HDVs can be positively improved at different vehicle levels, but the technology benefit and its economic feasibility are heavily dependent on the vehicle type and the operational cycle considered. The electrification pathway has the potential of reducing the carbon emission to a great extent, but the current battery technologies have proven to be not cost efficient for the heavy vehicles, because of the high purchase price and the low range, related to the battery cost and inferior energy density compared to conventional liquid fuels.   A scenario development model has been created in order to estimate and quantify the impact of future developments and emission reduction measures in Finland, Sweden and Norway for the timeframe 2016-2050, with a focus on 2030 results. Two scenarios concerning the powertrain developments of heavy-duty vehicles and buses have been created, a conservative scenario and electric scenario, as well as vehicle efficiency improvements and fuel consumption scenarios. Additional sets of parameters have been estimated as input for the model, such as national transport need and load assumptions. The results highlight the challenges of achieving the national GHG emission reduction targets with the current measures in all three countries. The slow fleet renewal rates and the high forecasted increase of transport need limit the benefits of alternative and more efficient powertrains introduced in the fleet by new vehicles. The heavy-duty transport is expected to maintain its heavy reliance on diesel fuel and hinder the improvements of the light-duty segments. A holistic approach is needed to reduce the GHG emissions from road transport, including more efficient powertrains, higher biofuel shares and progressive electrification.

Abstract

Tese de doutoramento em Sistemas Sustentáveis de Energia, apresentada ao Departamento de Engenharia Mecânica da Faculdade de Ciências e Tecnologia da Universidade de Coimbra The controversy raised around biofuels sustainability increased the pressure on biodiesel producers to be as cost efficient as possible and, simultaneously, ensure the sustainability of the biodiesel. As about 85% of biodiesel production costs are attributed to feedstock cost and each feedstock has a different environmental profile, operational level decision making about feedstock selection is crucial to reduce production costs and manage biodiesel environmental performance. This thesis explores opportunities to improve biodiesel cost effectiveness at the operational level, particularly in the feedstock selection process, by assessing the use of waste-based feedstocks (Waste Cooking Oil, WCO) in blends with conventional feedstocks (palm, rapeseed and soya) and hedging feedstock purchase, whilst managing environmental impacts. For this purpose, an uncertainty-aware decision aiding tool to assess economic and environmental tradeoffs of decisions at the operational level, addressing feedstock compositional and price uncertainty, was developed. The model combines environmental life-cycle assessment (LCA) with blending models using multi-objective optimization to assess water scarcity (WSI), water degradability – acidification (AA), eutrophication (EU), ecotoxicity (FT) and human toxicity (HT) – and Greenhouse Gas (GHG) emissions (CC). Data from different crop cultivation locations were considered: Colombia and Malaysia for palm; Argentina, Brazil and the United States (US) for soybean; and, Germany, France, Spain, Canada and the US for rapeseed. An approach was developed to facilitate the decision process that enables the decision-maker to select the best compromise feedstock blend based on an explicit overall environmental performance. Results show that incorporating feedstocks’ compositional uncertainty allows the use of WCO in blends with conventional feedstocks without compromising biodiesel technical performance. A reduction of total feedstock cost was obtained for blends with WCO relatively to equivalent (similar technical performance) blends composed only of virgin oils. The percentage of cost reduction depends on the relation among the prices of the feedstocks. Moreover, the use of WCO in the blends allows a reduction in cost variation reduction relatively to virgin oils blends because the price of that feedstock presents lower volatility comparatively to the conventional feedstocks. The differences observed in the environmental assessment of the various virgin oils systems are mainly related to water scarcity of the location, and the fertilization and pesticides schemes used in each crop/location. Results show that higher water scarcity footprint are due to both high water consumption and high water scarcity of the cultivation site. For the toxicity categories (HT and FT), the highest values are ascribed to the high quantity of pesticide used in the cultivation, while for CC, AA and EU the main contributor is the quantity of fertilizers. WCO presents the lowest values WSI, CC, EU and AA. The multi-objective analysis showed that lower CC and WSI solutions (blends) can be obtained at a lower cost if WCO is included in the biodiesel blend. The same conclusion is obtained when more environmental objectives (AA, EU, FT and HT) are considered in the analysis. The decision-aiding approach developed allows for the visualization of the tradeoff between cost and environmental impacts, facilitating the decision process when more than three objectives are at stake. This research shows that the inclusion of WCO in a diversified portfolio of feedstocks used in blending optimization models is an attractive approach to improve biodiesel cost effectiveness and environmental performance. The model developed can be further used to optimize the blending of alternative feedstocks and to assess the technical viability of other waste-based feedstock (e.g. animal fat) or emerging feedstocks such as algae. Although the tool was designed specifically for biodiesel production system, it can be adapted to other industries, particularly in the recycling sector, to support production planning at the operational level to enhance technical, economic and environmental performance of these industries. A controvérsia gerada em torno da sustentabilidade dos biocombustíveis aumentou a pressão nos produtores de biodiesel para serem o mais eficientes possível em termos de custos e, simultaneamente, garantirem a sustentabilidade do biodiesel. Como cerca de 85% do custo total de produção é atribuído ao custo da matéria-prima, e cada uma apresenta um perfil ambiental diferente, decisões ao nível operacional acerca de selecção de matéria-prima são cruciais para melhorar a performance económica e ambiental do biodiesel. Esta tese explora estratégias para reduzir custos de produção de biodiesel, particularmente no processo de selecção de matérias-primas, ao avaliar o uso de resíduos (Óleo Alimentar Usado, OAU) em misturas com óleos convencionais (soja, palma, colza) e planear a compra de matéria-prima, e, simultaneamente, gerir os impactes ambientais. Para tal, foi desenvolvida uma ferramenta de apoio à decisão para avaliar compromissos económicos e ambientais de decisões efectuadas ao nível operacional. Esta ferramenta tem em conta a incerteza associada à composição e ao preço da matéria-prima. O modelo desenvolvido combina Avaliação de Ciclo de Vida (ACV) ambiental com algoritmos de mistura através de optimização multiobjectivo para avaliar a escassez de água (WSI), degradabilidade da água – acidificação (AA), eutrofização (EU), ecotoxicidade (FT) e toxicidade humana (HT) – e, emissões de gases com efeito de estufa (CC). Diferentes locais de cultivo foram considerados: palma cultivada na Colômbia e Malásia; soja na Argentina, Brasil e Estados Unidos; e colza na Alemanha, França, Espanha, Canadá e Estados Unidos. Foi desenvolvida uma abordagem para facilitar o processo de decisão que permite ao decisor escolher a mistura com base na performance ambiental global. Os resultados mostram que é possível utilizar OAU em misturas com óleos virgens sem comprometer a qualidade do biodiesel se a incerteza composicional dos óleos for tida em conta. Estas misturas apresentam menores custos relativamente a misturas de óleos virgens. A percentagem de redução depende da relação entre os preços dos diferentes óleos. Adicionalmente, o uso de OAU nas misturas permite obter também uma redução na variação dos custos de produção porque o preço desta matéria-prima apresenta menor volatilidade relativamente à observada nos óleos convencionais. As diferenças observadas na avaliação ambiental dos diferentes óleos virgens estão relacionadas com a escassez de água da região e o esquema de fertilização/pesticidas usados em cada cultura/local. Os resultados mostram que pegadas hídricas mais elevadas devem-se simultaneamente a maiores consumos de água e elevada escassez dos locais de cultivo. Para as categorias de toxicidade (HT e FT), os valores mais elevados são devido à elevada quantidade de pesticidas utilizados no cultivo, enquanto que para CC, AA e EU a maior contribuição provém da quantidade de fertilizantes. WCO apresenta os menores valores para WSI, CC, EU e AA. Na análise multiobjectivo realizada, observou-se que soluções (misturas) com valores de CC e WSI mais baixos podem ser obtidos com menor custo se OAU for incluído nas misturas. A mesma conclusão é obtida quando mais objectivos ambientais (AA, EU, FT e HT) são considerados na análise. A ferramenta de apoio à decisão desenvolvida facilita o processo de decisão ao permitir a visualização do compromisso entre o objectivo económico e os ambientais quando mais do que três objectivos são considerados. Nesta investigação é evidenciado que a inclusão de OAU num portfólio diversificado de matérias-primas usado em modelos de optimização de misturas é uma abordagem atractiva para melhorar a performance económica e ambiental do biodiesel. O modelo desenvolvido pode ser utilizado para optimizar a mistura de matérias-primas alternativas e avaliar a viabilidade técnica de utilizar outros resíduos (por ex. gorduras animais) nas misturas. Embora a ferramenta tenha sido desenvolvida especificamente para produção de biodiesel, pode ser aplicada a outras indústrias, nomeadamente de reciclagem, para apoio à decisão no planeamento de produção com vista a melhorar a performance técnica, económica e ambiental dessas indústrias. Project EMSURE (Energy and Mobility for Sustainable Regions, CENTRO 07 0224 FEDER 002004) FEDER/FCT | PTDC/AGR-FOR/1510/2014 (POCI-01-0145-FEDER-016764) - SUSTAINFOR: Sustainability assessment of forest sector management strategies in the context of a bioeconomy FEDER/FCT | PTDC/AAG-MAA/6234/2014 (POCI-01-0145-FEDER-016765) - SABIOS: Sustainability assessment of bioenergy systems: a life-cycle multi-criteria decision-support approach, including land use change

Abstract

Electric vehicles (EV), both as battery electric vehicles (BEV) and plug-in hybrid electric vehicles (PHEV) have noteworthy potential to reduce global and local CO2 emissions. However, the fully exploitable potential depends on the actual vehicle kilometers travelled (VKT) that can be electrified. For BEV, the limited range excludes long-distance trips from electrification. For PHEV, long-distance trips are not excluded but the shorter electric driving range could reduce the miles electrified. The aim of the present paper is to compare the potential to electrify total VKT of BEV and PHEV. We use real-world driving data from several 780 German conventional passenger cars that are simulated as BEV and PHEV of different ranges. Furthermore, the CO2 emission reduction potential of both technologies and the influence of battery sizes are analyzed, by combining electrified kilometers with CO2 emission factors. We find PHEV to electrify more miles, both individual VKT as well as total VKT of the overall car fleet for given electric range. The difference in fleet electrification potential is maximal for about 30 km electric range. Compared to conventional vehicles both PHEV and BEV can significantly reduce well-to-wheel CO2 emissions when using renewable energies for recharging. The maximal reduction potential per vehicle is larger for PHEV and achieved at smaller range than for BEV.

Abstract

The article describes the methodology used to systematically enhance the Household Travel Surveys (HTS) with energy data on consumption, local pollutant emissions and greenhouse gas emissions in France. This is part of an approach called Mobility Emission Energy Diagnosis (MEED), which aims to facilitate the development of Urban Mobility Plans by providing a strategic diagnosis of environmental issues related to urban mobility of travellers. To obtain quality data that are comparable in time and space, a standardized methodology is proposed. This has been used systematically since 2014, and has already made it possible to link individual mobility behaviours with emissions of pollutants in about 25 towns, which represents about 15% of the French population. The method used is considered relevant and the database so constituted should be capable of generating many innovative analyses.

Abstract

"jats:p"This paper presents and analyses an innovative integrated scheme that aims to rationalize and improve the efficiency of urban freight transport as well as to promote reduced GHG emissions and traffic flows. Emissions management has become critical concern for modern companies and public authorities seeking to reduce carbon emissions and energy consumption from private and commercial heavy vehicle fleets, in line with the political targets of COP21 to COP23. The proposed scheme aims to utilize the current technological advances for efficient transport and logistics operations that regional authorities and companies can use and afford in order to provide competitive traffic management decisions as well as improvements in terms of pollutant emissions reduction. Both public and private stakeholders could interact to monitor and evaluate the impact of traffic policies and measures over time as well as the level of success of their routing strategies. Computational results on different scenarios of an experimental simulation model illustrate the competitiveness of the proposed scheme in an effort to quantify its effect. Document type: Article

Abstract

The annual reporting procedures of the United Nations Framework Convention on Climate Change (UNFCCC) have now produced greenhouse gas (GHG) emission inventories from 40 so-called Annex I countries for 18 years. This article analyses a subset of these data: emissions from road transport. The article compares the reported data with the technical guidance on GHG emission inventories provided by the Intergovernmental Panel on Climate Change (IPCC). The analysis suggests that some countries use the IPCC's default emission factors, whereas other countries use country-specific values. In the case of diesel-fuelled road transport, the estimated emissions appear to be generally comparable between all countries for all years. For CO2 emissions from gasoline-fuelled road transport, the picture is less clear. The results suggest that the default emission factor for CO2 from motor gasoline as provided by the IPCC is about 3-5% too low. Countries that seem to apply this default value might therefore underestimate their emissions by the same percentage. The effect of this possible underestimate on trends is, however, very small. Despite the possible problem with the default emission factor, the quantification of the trend in emissions is only slightly influenced by this. © 2011 Earthscan.

Abstract

The South African transport sector is estimated to emit 60 MtCO2eq and require 800 PJ of energy, similar in scale to industrial energy demand and emissions. The sector is forecast to potentially eclipse industry in this regard if conventional vehicle choices and travel modes persist. This paper explores scenarios of transport technology choices and demand in a future of uncertain fuel and technology costs, and the consequences for energy supply and greenhouse gas emissions. It explores the extent of electric vehicle (EV) adoption and the implication of fuel migration from petroleum products. The preference for alternative fuels such as hydrogen, liquid biofuels and natural gas is also investigated. The evolution of road transport in South Africa towards 2050 is investigated utilising the South African TIMES model, a full energy sector least-cost optimisation model that relies on a rich technological database of the entire energy supply and demand system. Hydrogen fuel cell vehicles are shown to be a viable option in freight and public transport, potentially meeting 70% of travel demand by 2045. The private passenger and light commercial sectors emerge as the main market for electric vehicles, potentially accounting for 80% of new vehicle sales by 2045. Electricity as a transport fuel could account for 30% of fuel supply and reduce transport emissions to half of present day estimates. However, the key uncertainty driving EV adoption is future vehicle costs and crude oil prices, which could dampen EV uptake. Another main finding is that petroleum-dependent vehicles remain an important vehicle class, and that re-investment in existing crude oil refineries to conform to Euro5 standards is a likely requirement. There seems to be little indication, however, that additional refining capacity would be economically viable within the planning horizon. Document type: Article

Abstract

The purpose of this article is to provide information to determine that telecommuting in Ecuador can be used as a measure of sustainable transport. Briefly, sustainable development is described, and certain definitions and approaches related to sustainable transport are covered, for instance, the Avoid-Shift-Improve (ASI) approach, as well as the Transport Demand Management (TDM), which serve to validate from a conceptual point of view the application and usefulness of telecommuting. An overview of the current situation in the transport sector in Ecuador is analyzed; the final energy demand; the environmental aspects related to transport, and the amount of public and private employees that are telecommuting. Taking into consideration some hypothesis, such as car ownership rate, the total amount of kilometers driven per year, the assumption of the distance travelled by employees who take public transportation; the assumptions helped to determine the savings that can be obtained through telecommuting in the present time. Therefore, these results would provide adequate information for decision makers to establish a conclusive pronouncement on whether or not support telecommuting as a valid working approach, and to develop the necessary policies to maintain it over time.