Current trends in diesel transport anticipate that in the upcoming future a range of renewable fuels will be necessary to comply with emission and sustainability legislations. Exhaust after-treatment devices such as diesel particulate filters –DPFs– will have to operate satisfactorily with this pool of biofuels. In particular, DPF regeneration is crucial to cut the fuel penalty and guarantee an acceptable lifetime for this device. In the present work, an automotive diesel engine was run with fossil fuel and three renewable fuels: a conventional biodiesel, a fuel manufactured through Fischer-Tropsch –FT– process and a HVO biofuel. The DPF was loaded and regenerated through an active process with fuel post-injections. Additionally, soot samples were investigated with thermo-gravimetry (TGA) and calorimetry (DSC) to confirm whether these techniques obtain relevant information for explaining DPF behavior. Both methods proved that biodiesel leads to a more economical regeneration being the biodiesel soot, more reactive than the other samples, the main reason. DPF regenerations with paraffinic fuels (FT-derived and HVO) did not reveal strong differences compared to diesel, though TGA and DSC results suggested that soot from paraffinic biofuels is more reactive than that from diesel. The exhaust gas temperature and composition are behind this apparent discrepancy.

This study is a part of a poly generation project which will use animal waste or agricultural waste to produce biogas and will provide cooking gas, electricity and arsenic free clean water for drinking in rural areas of Bangladesh.  The study mainly analyzes the cooking and lighting energy demand of households across different income groups in a village named “Pani Para” in the Faridpur district in Bangladesh and also looks at the potential of biogas in the village. It has been done by adopting case study method and conducting a survey in the village using a questionnaire. Fuel mix across different income groups for meeting their cooking and lighting energy needs have also been studied along with socio-economic situation of the villagers and their preferences to change their current cooking fuel utilization patterns. Various scenarios like variation in fuel consumption patterns, priority of income expenditure and access to fuel with income level have been examined. The study also focuses to analyze the awareness of the villagers about biogas technology and their willingness to contribute for the poly generation project along with the willingness of households to pay for embracing change in current cooking and lighting fuels. Biomass potential i.e. cow dung and agricultural waste is also calculated in the surveyed village along with the production of biogas from the available biomass resources. The scenarios to provide the cooking gas, electricity and clean water through biogas poly generation project from the available resources are also investigated. Analysis reveals that the total energy consumption (cooking and lighting) increases with the increase in the income level among the households. Average household cooking and lighting energy demand by low, medium and high income groups is 8492 kWh/yr, 9789 kWh/yr and 14806 kWh/yr respectively. Cooking energy demand and agricultural waste consumption also show an increasing trend with the increase in land holding size. Among the income expenditure priorities food is one of the most important priorities and energy being less important due to availability of biomass at little or no cost. Awareness of biogas technology among the households and willingness to contribute for the poly generation plant shows an increasing trend with the increase in education level. The study shows that there is a positive response of the villagers for being willing to embrace the change in the current cooking patterns as well as welcoming new technologies that could support such a change. It was found that the cow dung resource in the village is not enough to produce sufficient biogas for the poly generation project. With the incorporation of the agricultural waste with the cow dung, biogas production comes quite close to requirement of the poly generation plant but however could not suffice it completely due to the lack of raw material in the studied village. In that case the scenario of providing electricity and clean water to all the villagers and providing all the three facilities to the 2/3rd of households is investigated. 1/3rd of the low income households then could meet their cooking demands by provision of improved cooking stoves as cooking gas could not be provided to them due to limited feedstock. The study shows that despite of the fact that cooking and lighting energy needs increase with income but there is not much variation in the fuel mix and almost everyone in the village rely on biomass to meet their energy demand. It is because there is very limited access to the modern fuel for cooking and no electricity access in the village, so the households have to rely on the traditional fuels. / <p>KTH School of Industrial Engineering and Management, Department of Energy Technology, Division of Energy and Climate studies</p>

Climate change threatens global food security by increasing extreme-weather shocks and reducing the productivity of major global crops. While recent research has highlighted the risk of rising extreme heat, comparatively little is known about how the intensity distribution of rainfall, and rainfall’s interactions with heat, influence global crops. Further, as the broader climate transition gains momentum, the industrial activities needed to mitigate and adapt to climate change will emit CO₂. These emissions remain unquantified and largely ignored in research and policy, and thus present an under-assessed risk to crops and society at large.This thesis advances the understanding of present and future agricultural risks from two aspects of hydroclimatic complexity: hourly rainfall intensity and temperature-moisture (T-M) couplings. Both aspects are expected to shift under climate change, with highly uncertain crop impacts. It further simulates the adaptation and mitigation emissions embedded in the broader climate transition, illuminating a previously under-appreciated benefit of enhance climate ambition. Climate warming is expected to intensify rainfall, decreasing the frequency of drizzle while boosting heavy and extreme events. I show that surprisingly heavy rainfall is optimal for US maize and soy yields, with yield loss due to drizzle and very extreme downpours. As a result, the future concentration of rainfall into fewer, heavier hourly events will benefit crop yields 2-3%, partly offsetting larger damages from warming. T-M couplings arising from land-air interactions and atmospheric circulation may shift under 21st Century warming, altering the likelihood of concurrent heat and drought extremes, with uncertain risks to crops. I demonstrate that maize and soy grown in regions with strong T-M couplings historically suffered enhanced crop sensitivity to heat. These couplings will strengthen over most of global croplands this century, worsening the impact of warming on crops by 5% globally, with large regional variations. The energetic demands of the broader climate transition – such as steel for wind turbines, and concrete for coastal barriers – will initially be satisfied by fossil fuels. I show that simulated mitigation and adaptation will emit 185GtCO₂ by 2100 under a transition path consistent with current policies (~2.7°C warming by 2100), equivalent to half the remaining carbon budget for 1.5°C. However, these emissions can be reduced by 90% under a 1.5°C transition path, a previously unidentified co-benefit of enhanced climate ambition.

No description available.

Développer de nouvelles sources d’énergie respectueuses de l’environnement est un des enjeux majeur de nos sociétés développées. Pour espérer la pérennité de notre espèce sur cette planète, il est indispensable de développer les sources d'énergie renouvelable ; permettant de nous affranchir de la dépendance aux énergies fossiles polluantes et dont les stocks s’épuisent. Il appartient aux scientifiques d’apporter leurs contributions à cet important défi que l’on appelle la transition énergétique et pour ça d’aider à développer une énergie idéale qui ne produirait pas de déchet polluant, serait très efficace et largement disponible. L'énergie solaire représente un excellent candidat car elle est de loin la plus abondante et prometteuse source d’énergie propre. D'importants efforts sont donc menés pour développer les technologies solaires, notamment la photosynthèse artificielle.La photosynthèse artificielle a vu le jour il y a une centaine d’années et fait l’objet de beaucoup d’intérêt et de recherche. Cette technologie cherche à imiter la photosynthèse naturelle réalisée par les plantes; et cela afin de stocker l’énergie provenant du Soleil dans des composés utilisables par l’Homme. La photosynthèse artificielle consiste en l’élaboration de systèmes synthétiques capables sous impulsion lumineuse de réaliser la décomposition de l’eau de manière catalytique, pour générer du dihydrogène ou des produits issus de la réduction du CO2, que l’on appelle combustibles solaires car à haut potentiel énergétique. En effet, la photosynthèse débute par la photo-catalyse de l’oxydation de l’eau, qui permet d’extirper les électrons et les protons des molécules d’eau. Ce sont ces électrons et protons qui seront utilisés par un catalyseur pour produire les combustibles solaires.Depuis peu, une véritable volonté de comprendre les mécanismes qui ont lieu lors de ces réactions catalysées semble apparaitre. Ces réactions mettent en jeu des transferts électroniques multiples photo-induits et cela rend leur étude assez compliquée. Grâce à des avancées technologiques importantes, nous avons étudié de manière plus approfondies plusieurs systèmes photo-catalytiques afin d’en tirer des savoirs permettant de rationaliser le design et d’améliorer les capacités des futurs systèmes développés. Ces avancées techniques ont été possibles grâce à des collaborations interdisciplinaires entre des chimistes et des physiciens et ont permis de développer un montage d’absorption transitoire « double-pump» afin de caractériser les espèces transitoires formées et de retracer les mécanismes lors de deux transferts électroniques photo-induits successifs.Dans la seconde partie de ce travail, de nouveaux catalyseurs ont été développé pour la réaction de photo-catalyse de l’oxydation de l’eau. La majorité des études menées jusqu’ici sur le sujet ont porté sur des systèmes moléculaires, mais le manque de robustesse et de réutilisabilité des catalyseurs homogènes a poussé la recherche vers le domaine des matériaux. Ainsi depuis une quarantaine d’années des systèmes photo-catalytiques hétérogènes ont été développé. Nous avons explorés deux types de matériaux, des nanoparticules catalyseurs dans des systèmes photo-catalytiques, et des polymères qui à eux seuls sont capables de réaliser l’ensemble des fonctions nécessaires à la photo-catalyse d’une réaction telle que l’oxydation de l’eau sous irradiation de lumière visible.Ainsi au cours de cette thèse nous avons tenté par deux approches d’avancer les connaissances et le développement de la photosynthèse artificielle. Une solution encore peu développée au problème énergétique auquel notre société fait face est le recours aux combustibles solaires, et il est grand temps que la recherche avance et que la transition énergétique s’impose plus efficacement et largement. / Developpment of environment-friendly sources of energy is one of the stakes major for our societies. To hope for the sustainability of Humans on Earth, it is essential to change our consumer habits on energetics by breaking our dependance on fossil fuels, which use leads to ecological desasters and which stocks are running out. The key of this important challenge is the growth of renewable energy sources, and this is called energy transition. The ideal energy would not produce any polluting waste, would be efficient and widely available. Solar energy is an excellent candidate because it is by far the most abundant and promising source of clean energy. Thus, important efforts are made to developp the solar technologies, including artificial photosynthesis.Artificial photosynthesis was created a century ago and is the focus of many interests and researchs. This technology aims at mimicking the natural photosynthesis realized by plants ; and that in order to store the energy coming from the Sun irriadiation in compounds that can be used at demand. Artificial photosynthesis consists in the elaboration of synthetic systems able under light impulsion to realize the water splitting/decomposition reactions in a catalytique way, generating hydrogène or CO2 reduction products, which are called solar fuels thanks to their high energetic potentials. Indeed, photosynthesis begins with the photo-catalysis of water oxidation, which extirpates the electrons and protons of water molecules. And it is these electrons and protons which will be used to produce the solar fuels.Recently, a real commitment to understand deaply the mechanisms that take place during these catalysed reactions seems to appear. These transformations involve multiple photo-induced electron transfers and it returns their study relatively complicated. Thanks to technological breakthroughs, we studied in a thorough way several photocatalytic systems to draw knowledges ; allowing the rationalisation of the design and then the efficiency improvement of future developped systems. These technical advances were possible thanks to interdisciplinary collaborations between chemists and physicists and led to the developpment of a set-up of « double-pump » transient absorption, that enables to characterize the transient species formed and to track down the pathways during two successive photoinduced electron transfers.In the second part of this work, new catalysts were developped for the photocatalysis of water oxidation reaction. The big majority of the studies led so far on this subject concerned molecular systems, but the lack of robustness and reusability of homogeneous catalysts pushed the research towards materials area. Since about forty years, heterogeneous systems were developped for photocatalysis of several reactions. We explored two types of materials, nanoparticules as catalyst in photocatalytic systems ; and polymers that are able on their own to realize all the functions required for the photocatalysis of a reaction such as water oxidation under visible light irradiation.Thus, during this PhD we tried by two approaches to increase the knowledges and the development of artificial photosynthesis. A solution that is still under-developped to fix the energetic issue our society is facing to, is the use of solar fuels ; and it’s imperative for the research to move forward and that energy transition prevails more effectively and widely.

In spruce-fir forests, there are many biotic and abiotic disturbances that can alter stand structure and composition. Many of these disturbances can produce high percentages of tree mortality at different scales. Spruce beetle has been considered a devastating disturbance agent, capable of creating high levels of mortality that will alter fuel complexes that may affect fire behavior. For comparison, stand data were gathered in endemic (near Loa and Moab, UT), epidemic (near Loa and Fairview, UT), and post-epidemic (near Salina and Loa, UT) condition classes of spruce beetle activity. Generally, fine fuels were higher during the epidemic and returned to background levels during post-epidemic conditions. Also, herbaceous and shrub components increase following outbreak situations with an initial pulse of herbaceous material during epidemics followed by the expansion of shrub material in post-epidemic areas. Fuel bed bulk depth, large diameter woody material, sound and rotten, and duff did not significantly differ between spruce beetle condition classes. Available live canopy fuel, canopy bulk density, and canopy base height were significantly reduced from endemic when compared to epidemic and post-epidemic condition classes. The fuel complex alterations resulted in changes to calculated surface and crown fire behavior. Crown base height decreased in post-epidemic classes, which allowed for easier crown fire initiation. Due to large gaps in canopy continuity, no active crown fire was initiated. In endemic situations, canopy bulk density was adequate to maintain active crown fire runs, but crown base height was too high to initiate crown fire. Surface fire, estimated from the custom fuel models following fuel complex alterations, showed that fireline intensity and rates of spread were greater in post-epidemic areas, but mostly due to reduced overstory sheltering. When custom fuel models were compared with similar mid-flame wind speeds, epidemic and post-epidemic fire behavior predictions were similar, indicating that reduced sheltering was more dominant than the influence of the fuels complex or solar radiation. When custom fuel models were compared with established fuel models, none predicted the same fire behavior outputs.

No description available.

Child mortality in sub-Saharan Africa is reducing but the levels remain high with subnational within-country variations. Birth weight is a key predictor of child survival and monitoring birth weight outcomes, in particular, prevalence of low birth weights, is important for resource allocation to improve child survival outcomes. Past research in sub-Saharan Africa has found that different individual-level factors are associated with birth weight including BMI of mother, sex of baby, educational level of mother, and wealth index of household. Some environmental factors are found to be associated with birth outcomes. However, past findings regarding the association of birth weight with household air pollution (HAP) resulting from cooking fuels are non-conclusive. In this study, we analyze variability in birth weights subnationally for Ghana and assess its association with household air pollution resulting from cooking fuels, accounting for variation due to other factors including maternal and household predictors, as well as geographical location. The analysis was based on birth weights for 1310 births, obtained from data collected in 2014 in the Demographic and Health Survey (DHS). We use Bayesian spatial regression models to estimate associations and capture spatial variation. Spatial variation was captured with a conditional autoregressive (CAR) model. Based on various models, we do not find evidence to suggest that cooking fuel is associated with birth weight. After accounting for covariates, the average birth weights per district ranged from 2823g (95% CI: 2613g, 3171g) in Ketu district to 3243g (95% CI: 3083g, 3358g) in Ashanti Akim North district. Across Ghana, difference in birth weight attributable to district spatial effects range from -33g in Lawra district in Upper West region of Ghana to 11g in Ho in the Volta region.

Three troublesome issues concerning residential curbside collection (RCC) and municipal solid waste (MSW) management systems in the United States motivated this research. First, reliance upon inefficient collection and scheduling procedures negatively affect RCC efficiency, greenhouse gas (GHG) emissions, and cost. Second, the neglected impact of MSW management practices on water resources. Third, the implications of alternative fuels on the environmental and financial performance of waste collection where fuel plays a significant rule. The goal of this study was to select the best RCC program, MSW management practice, and collection fuel. For this study, field data were collected for RCC programs across the State of Florida. The garbage and recyclables generation rates were compared based on garbage collection frequency and use of dual-stream (DS) or single-stream (SS) recyclables collection system. The assessment of the collection programs was evaluated based on GHG emissions, while for the first time, the water footprint (WFP) was calculated for the most commonly used MSW management practices namely landfilling, combustion, and recycling. In comparing alternative collection fuels, two multi-criteria decision analysis (MCDA) tools, TOPSIS and SAW, were used to rank fuel alternatives for the waste collection industry with respect to a multi-level environmental and financial decision matrix. The results showed that SS collection systems exhibited more than a two-fold increase in recyclables generation rates, and a ~2.2-fold greater recycling efficiency compared to DS. The GHG emissions associated with the studied collection programs were estimated to be between 36 and 51 kg CO2eq per metric ton of total household waste (garbage and recyclables), depending on the garbage collection frequency, recyclables collection system (DS or SS) and recyclables compaction. When recyclables offsets were considered, the GHG emissions associated with programs using SS were estimated between -760 and -560, compared to between -270 and -210 kg CO2eq per metric ton of total waste for DS programs. In comparing the WFP of MSW management practices, the results showed that the WFP of waste landfilling can be reduced through implementing bioreactor landfilling. The WFP of electricity generated from waste combustion was less than the electricity from landfill gas. Overall, the WFP of electricity from MSW management practices was drastically less than some renewable energy sources. In comparing the WFP offsets of recyclables, the recycling of renewable commodities, e.g. paper, contributed to the highest WFP offsets compared to other commodities, mainly due to its raw material acquisition high WFPs. This suggests that recycling of renewable goods is the best management practice to reduce the WFP of MSW management. Finally, the MCDA of alternative fuel technologies revealed that diesel is still the best option, followed by hydraulic-hybrid waste collection vehicles (WCVs), then landfill gas (LFG) sourced natural gas, fossil natural gas and biodiesel. The elimination of the fueling station criterion from the financial criteria ranked LFG-sourced natural gas as the best option; suggesting that LFG sourced natural gas is the best alternative to fuel WCV when accessible. In conclusion, field data suggest that RCC system design can significantly impact recyclables generation rate and efficiency, and consequently determine environmental and economic impact of collection systems. The WFP concept was suggested as a method to systematically assess the impact of MSW management practices on water resources. A careful consideration of the WFP of MSW management practices and energy recovered from MSW management facilities is essential for the sustainable appropriation of water resources and development.

Autoignition and oxidation of two Methane (CH4) and Dimethyl Ether (CH3OCH3 or DME) mixtures in air were studied in shock tubes over a wide range of equivalence ratios at elevated temperatures and pressures. These experiments were conducted in the reflected shock region with pressures ranging from 0.8 to 35.7 atmospheres, temperatures ranging from 913 to 1650 K, and equivalence ratios of 2.0, 1.0, 0.5, and 0.3. Ignition delay times were obtained from shock-tube endwall pressure traces for fuel mixtures of CH4/CH3OCH3 in ratios of 80/20 percent volume and 60/40 percent volume, respectively. Close examination of the data revealed that energy release from the mixture is occurring in the time between the arrival of the incident shock wave and the ignition event. An adjustment scheme for temperature and pressure was devised to account for this energy release and its effect on the ignition of the mixture. Two separate ignition delay correlations were developed for these pressure- and temperature-adjusted data. These correlations estimate ignition delay from known temperature, pressure, and species mole fractions of methane, dimethyl ether, and air (0.21 O2 + 0.79 N2). The first correlation was developed for ignition delay occurring at temperatures greater than or equal to 1175 K and pressures ranging from 0.8 to 35.3 atm. The second correlation was developed for ignition delay occurring at temperatures less than or equal to 1175 K and pressures ranging from 18.5 to 40.0 atm. Overall good agreement was found to exist between the two correlations and the data of these experiments. Findings of these experiments also include that with pressures at or below ten atm, increased concentrations of dimethyl ether will consistently produce faster ignition times. At pressures greater than ten atmospheres it is possible for fuel rich mixtures with lower concentrations of dimethyl ether to give the fastest ignition times. This work represents the most thorough shock tube investigation for oxidation of methane with high concentration levels of dimethyl ether at gas turbine engine relevant temperatures and pressures. The findings of this study should serve as a validation for detailed chemical kinetics mechanisms.