Matching Items (19)

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CO2 Reduction via Functionalized Protein/Organometallic Complexes

Description

As prices for fuel along with the demand for renewable resources grow, it becomes of paramount importance to develop new ways of obtaining the energy needed to carry out the

As prices for fuel along with the demand for renewable resources grow, it becomes of paramount importance to develop new ways of obtaining the energy needed to carry out the tasks we face daily. Costs of production due to energy and time constraints impose severe limitations on what is viable. Biological systems, on the other hand, are innately efficient both in terms of time and energy by handling tasks at the molecular level. Utilizing this efficiency is at the core of this research. Proper manipulation of even common proteins can render complexes functionalized for specific tasks. In this case, the coupling of a rhenium-based organometallic ligand to a modified myoglobin containing a zinc porphyrin, allow for efficient reduction of carbon dioxide, resulting in energy that can be harnessed and byproducts which can be used for further processing. Additionally, a rhenium based ligand functionalized via biotin is tested in conjunction with streptavidin and ruthenium-bipyridine.

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Date Created
  • 2014-12

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Direct and indirect ecological consequences of human activities in urban and native ecosystems

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Though cities occupy only a small percentage of Earth's terrestrial surface, humans concentrated in urban areas impact ecosystems at local, regional and global scales. I examined the direct and

Though cities occupy only a small percentage of Earth's terrestrial surface, humans concentrated in urban areas impact ecosystems at local, regional and global scales. I examined the direct and indirect ecological outcomes of human activities on both managed landscapes and protected native ecosystems in and around cities. First, I used highly managed residential yards, which compose nearly half of the heterogeneous urban land area, as a model system to examine the ecological effects of people's management choices and the social drivers of those decisions. I found that a complex set of individual and institutional social characteristics drives people's decisions, which in turn affect ecological structure and function across scales from yards to cities. This work demonstrates the link between individuals' decision-making and ecosystem service provisioning in highly managed urban ecosystems.

Second, I examined the distribution of urban-generated air pollutants and their complex ecological outcomes in protected native ecosystems. Atmospheric carbon dioxide (CO2), reactive nitrogen (N), and ozone (O3) are elevated near human activities and act as both resources and stressors to primary producers, but little is known about their co-occurring distribution or combined impacts on ecosystems. I investigated the urban "ecological airshed," including the spatial and temporal extent of N deposition, as well as CO2 and O3 concentrations in native preserves in Phoenix, Arizona and the outlying Sonoran Desert. I found elevated concentrations of ecologically relevant pollutants co-occur in both urban and remote native lands at levels that are likely to affect ecosystem structure and function. Finally, I tested the combined effects of CO2, N, and O3 on the dominant native and non-native herbaceous desert species in a multi-factor dose-response greenhouse experiment. Under current and predicted future air quality conditions, the non-native species (Schismus arabicus) had net positive growth despite physiological stress under high O3 concentrations. In contrast, the native species (Pectocarya recurvata) was more sensitive to O3 and, unlike the non-native species, did not benefit from the protective role of CO2. These results highlight the vulnerability of native ecosystems to current and future air pollution over the long term. Together, my research provides empirical evidence for future policies addressing multiple stressors in urban managed and native landscapes.

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Date Created
  • 2014

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Investigating the Thermodynamic Cycle and Efficiency of the Thermal Hydraulic Engine

Description

About 20-50% of industrial processes energy is lost as waste heat in their operations. The thermal hydraulic engine relies on the thermodynamic properties of supercritical carbon dioxide (CO2) to efficiently

About 20-50% of industrial processes energy is lost as waste heat in their operations. The thermal hydraulic engine relies on the thermodynamic properties of supercritical carbon dioxide (CO2) to efficiently perform work. Carbon dioxide possesses great properties that makes it a safe working fluid for the engine’s applications. This research aims to preliminarily investigate the actual efficiency which can be obtained through experimental data and compare that to the Carnot or theoretical maximum efficiency. The actual efficiency is investigated through three approaches. However, only the efficiency results from the second method are validated since the other approaches are based on a complete actual cycle which was not achieved for the engine. The efficiency of the thermal hydraulic engine is found to be in the range of 0.5% to 2.2% based on the second method which relies on the boundary work by the piston. The heating and cooling phases of the engine’s operation are viewed on both the T-s (temperature-entropy) and p-v (pressure-volume) diagrams. The Carnot efficiency is also found to be 13.7% from a temperature difference of 46.20C based on the measured experimental data. It is recommended that the thermodynamic cycle and efficiency investigation be repeated using an improved heat exchanger design to reduce energy losses and gains during both the heating and cooling phases. The temperature of CO2 can be measured through direct contact with the thermocouple and pressure measurements can be improved using a digital pressure transducer for the thermodynamic cycle investigation.

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Date Created
  • 2020

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Examining a sustainable approach to global climate change policy

Description

The United Nation's Framework Convention on Climate Change (UNFCCC) recognizes development as a priority for carbon dioxide (CO2) allocation, under its principle of "common but differentiated responsibilities". This was codified

The United Nation's Framework Convention on Climate Change (UNFCCC) recognizes development as a priority for carbon dioxide (CO2) allocation, under its principle of "common but differentiated responsibilities". This was codified in the Kyoto Protocol, which exempt developing nations from binding emission reduction targets. Additionally, they could be the recipients of financed sustainable development projects in exchange for emission reduction credits that the developed nations could use to comply with emission targets. Due to ineffective results, post-Kyoto policy discussions indicate a transition towards mitigation commitments from major developed and developing emitters, likely supplemented by market-based mechanisms to reduce mitigation costs. Although the likelihood of achieving substantial emission reductions is increased by the new plan, there is a paucity of consideration to how an ethic of development might be advanced. Therefore, this research empirically investigates the role that CO2 plays in advancing human development (in terms of the Human Development Index or HDI) over the 1990 to 2010 time period. Based on empirical evidence, a theoretical CO2-development framework is established, which provides a basis for designing a novel policy proposal that integrates mitigation efforts with human development objectives. Empirical evidence confirms that CO2 and HDI are highly correlated, but that there are diminishing returns to HDI as per capita CO2 emissions increase. An examination of development pathways reveals that as nations develop, their trajectories generally become less coupled with CO2. Moreover, the developing countries with the greatest gains in HDI are also nations that have, or are in the process of moving toward, outward-oriented trade policies that involve increased domestic capabilities for product manufacture and export. With these findings in mind, future emission targets should reduce current emissions in developed nations and allow room for HDI growth in developing countries as well as in the least developed nations of the world. Emission trading should also be limited to nations with similar HDI levels to protect less-developed nations from unfair competition for capacity building resources. Lastly, developed countries should be incentivized to invest in joint production ventures within the LDCs to build capacity for self-reliant and sustainable development over the long-term.

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Date Created
  • 2013

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Moving towards sustainable and resilient smart water grids: networked sensing and control devices in the urban water system

Description

Urban water systems face sustainability challenges ranging from water quality, leaks, over-use, energy consumption, and long-term supply concerns. Resiliency challenges include the capacity to respond to drought, managing pipe deterioration,

Urban water systems face sustainability challenges ranging from water quality, leaks, over-use, energy consumption, and long-term supply concerns. Resiliency challenges include the capacity to respond to drought, managing pipe deterioration, responding to natural disasters, and preventing terrorism. One strategy to enhance sustainability and resiliency is the development and adoption of smart water grids. A smart water grid incorporates networked monitoring and control devices into its structure, which provides diverse, real-time information about the system, as well as enhanced control. Data provide input for modeling and analysis, which informs control decisions, allowing for improvement in sustainability and resiliency. While smart water grids hold much potential, there are also potential tradeoffs and adoption challenges. More publicly available cost-benefit analyses are needed, as well as system-level research and application, rather than the current focus on individual technologies. This thesis seeks to fill one of these gaps by analyzing the cost and environmental benefits of smart irrigation controllers. Smart irrigation controllers can save water by adapting watering schedules to climate and soil conditions. The potential benefit of smart irrigation controllers is particularly high in southwestern U.S. states, where the arid climate makes water scarcer and increases watering needs of landscapes. To inform the technology development process, a design for environment (DfE) method was developed, which overlays economic and environmental performance parameters under different operating conditions. This method is applied to characterize design goals for controller price and water savings that smart irrigation controllers must meet to yield life cycle carbon dioxide reductions and economic savings in southwestern U.S. states, accounting for regional variability in electricity and water prices and carbon overhead. Results from applying the model to smart irrigation controllers in the Southwest suggest that some areas are significantly easier to design for.

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Date Created
  • 2012

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Towards biohybrid artificial photosynthesis

Description

A vast amount of energy emanates from the sun, and at the distance of Earth, approximately 172,500 TW reaches the atmosphere. Of that, 80,600 TW reaches the surface with 15,600

A vast amount of energy emanates from the sun, and at the distance of Earth, approximately 172,500 TW reaches the atmosphere. Of that, 80,600 TW reaches the surface with 15,600 TW falling on land. Photosynthesis converts 156 TW in the form of biomass, which represents all food/fuel for the biosphere with about 20 TW of the total product used by humans. Additionally, our society uses approximately 20 more TW of energy from ancient photosynthetic products i.e. fossil fuels. In order to mitigate climate problems, the carbon dioxide must be removed from the human energy usage by replacement or recycling as an energy carrier. Proposals have been made to process biomass into biofuels; this work demonstrates that current efficiencies of natural photosynthesis are inadequate for this purpose, the effects of fossil fuel replacement with biofuels is ecologically irresponsible, and new technologies are required to operate at sufficient efficiencies to utilize artificial solar-to-fuels systems. Herein a hybrid bioderived self-assembling hydrogen-evolving nanoparticle consisting of photosystem I (PSI) and platinum nanoclusters is demonstrated to operate with an overall efficiency of 6%, which exceeds that of land plants by more than an order of magnitude. The system was limited by the rate of electron donation to photooxidized PSI. Further work investigated the interactions of natural donor acceptor pairs of cytochrome c6 and PSI for the thermophilic cyanobacteria Thermosynechococcus elogantus BP1 and the red alga Galderia sulphuraria. The cyanobacterial system is typified by collisional control while the algal system demonstrates a population of prebound PSI-cytochrome c6 complexes with faster electron transfer rates. Combining the stability of cyanobacterial PSI and kinetics of the algal PSI:cytochrome would result in more efficient solar-to-fuel conversion. A second priority is the replacement of platinum with chemically abundant catalysts. In this work, protein scaffolds are employed using host-guest strategies to increase the stability of proton reduction catalysts and enhance the turnover number without the oxygen sensitivity of hydrogenases. Finally, design of unnatural electron transfer proteins are explored and may introduce a bioorthogonal method of introducing alternative electron transfer pathways in vitro or in vivo in the case of engineered photosynthetic organisms.

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Date Created
  • 2014

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Reframing the Climate Change Problem: Evaluating the Political, Technological, and Ethical Management of Carbon Dioxide Emissions in the United States

Description

Research confirms that climate change is primarily due to the influx of greenhouse gases from the anthropogenic burning of fossil fuels for energy. Carbon dioxide (CO2) is the dominant greenhouse

Research confirms that climate change is primarily due to the influx of greenhouse gases from the anthropogenic burning of fossil fuels for energy. Carbon dioxide (CO2) is the dominant greenhouse gas contributing to climate change. Although research also confirms that negative emission technologies (NETs) are necessary to stay within 1.5-2°C of global warming, this dissertation proposes that the climate change problem has been ineffectively communicated to suggest that CO2 emissions reduction is the only solution to climate change. Chapter 1 explains that current United States (US) policies focus heavily on reducing CO2 emissions, but ignore the concentrations of previous CO2 emissions accumulating in the atmosphere. Through political, technological, and ethical lenses, this dissertation evaluates whether the management process of CO2 emissions and concentrations in the US today can effectively combat climate change.

Chapter 2 discusses the historical management of US air pollution, why CO2 is regulated as an air pollutant, and how the current political framing of climate change as an air pollution problem promotes the use of market-based solutions to reduce emissions but ignores CO2 concentrations. Chapter 3 argues for the need to reframe climate change solutions to include reducing CO2 concentrations along with emissions. It presents the scientific reasoning and technological needs for reducing CO2 concentrations, why direct air capture (DAC) is the most effective NET to do so, and existing regulatory systems that can inform future CO2 removal policy. Chapter 4 explores whether Responsible Innovation (RI), a framework that includes society in the innovation process of emerging technologies, is effective for the ethical research and deployment of DAC; reveals the need for increased DAC governance strategies, and suggests how RI can be expanded to allow continued research of controversial emerging technologies in case of a climate change emergency. Overall, this dissertation argues that climate change must be reframed as a two-part problem: preventing new CO2 emissions and reducing concentrations, which demands increased investment in DAC research, development, and deployment. However, without a national or global governance strategy for DAC, it will remain difficult to include CO2 concentration reduction as an essential piece to the climate change solution.

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Date Created
  • 2020

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Techno-Economic Analysis of Capturing Carbon Dioxide from the Air: Positioning the Technology in the Energy Infrastructure of the Future

Description

As the global community raises concerns regarding the ever-increasing urgency of climate change, efforts to explore innovative strategies in the fight against this anthropogenic threat is growing. Along with other

As the global community raises concerns regarding the ever-increasing urgency of climate change, efforts to explore innovative strategies in the fight against this anthropogenic threat is growing. Along with other greenhouse gas mitigation technologies, Direct Air Capture (DAC) or the technology of removing carbon dioxide directly from the air has received considerable attention. As an emerging technology, the cost of DAC has been the prime focus not only in scientific society but also between entrepreneurs and policymakers. While skeptics are concerned about the high cost and impact of DAC implementation at scales comparable to the magnitude of climate change, industrial practitioners have demonstrated a pragmatic path to cost reduction. Based on the latest advancements in the field, this dissertation investigates the economic feasibility of DAC and its role in future energy systems. With a focus on the economics of carbon capture, this work compares DAC with other carbon capture technologies from a systemic perspective. Moreover, DAC’s major expenses are investigated to highlight critical improvements necessary for commercialization. In this dissertation, DAC is treated as a backstop mitigation technology that can address carbon dioxide emissions regardless of the source of emission. DAC determines the price of carbon dioxide removal when other mitigation technologies fall short in meeting their goals. The results indicate that DAC, even at its current price, is a reliable backup and is competitive with more mature technologies such as post-combustion capture. To reduce the cost, the most crucial component of a DAC design, i.e., the sorbent material, must be the centerpiece of innovation. In conclusion, DAC demonstrates the potential for not only negative emissions (carbon dioxide removal with the purpose of addressing past emissions), but also for addressing today’s emissions. The results emphasize that by choosing an effective scale-up strategy, DAC can become sufficiently cheap to play a crucial role in decarbonizing the energy system in the near future. Compared to other large-scale decarbonization strategies, DAC can achieve this goal with the least impact on our existing energy infrastructure.

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Date Created
  • 2020

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Optimizing the process parameters for electrochemical reduction of carbon dioxide

Description

One the major problems of this modern industrialized world is its dependence on fossil fuels for its energy needs. Burning of fossils fuels generates green-house gases which have adverse effects

One the major problems of this modern industrialized world is its dependence on fossil fuels for its energy needs. Burning of fossils fuels generates green-house gases which have adverse effects on global climate contributing to global warming. According to Environmental Protection Agency (EPA), carbon dioxide makes up 80 percent of green-house gases emitted in USA. Electrochemical reduction of carbon dioxide is an approach which uses CO2 emissions to produce other useful hydrocarbons which can be used in many ways.

In this study, primary focus was on optimizing the operating conditions, determining the better catalyst material, and analyzing the reaction products for the process of electrochemical reduction of carbon dioxide (ERC). Membrane electrode assemblies (MEA’s) are developed by air bushing the metal particles with a spray gun on to Nafion-212 which is a solid polymer based electrolyte (SPE), to support the electrodes in the electrochemical reactor gas diffusion layers (GDL) are developed using porous carbon paper. Anode was always made using the same material which is platinum but cathode material was changed as it is the working electrode.

The membrane electrode assembly (MEA) is then placed into the electrochemical reactor along with gas diffusion layer (GDL) to assess the performance of the catalyst material by techniques like linear sweep voltammetry and chronoamperometry. Performance of MEA was analyzed at 4 different potentials, 2 different temperatures and for 2 different cathode catalyst materials. The reaction products of the process are analyzed using gas chromatography (GC) which has thermal conductivity detector (TCD) used for detecting hydrogen (H2), carbon monoxide (CO) and flame ionization detector (FID) used for detecting hydrocarbons. The experiments performed at 40o C gave the better results when compared with the experiments performed at ambient temperature. Also results suggested that copper oxide cathode catalyst has better durability than platinum-carbon. Maximum faradaic efficiency for methane was 5.3% it was obtained at 2.25V using copper oxide catalyst. Furthermore, experiments must be carried out to make the electrochemical reactor more robust to withstand all the operating conditions like higher potentials and to make it a solar powered reactor.

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Date Created
  • 2017

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Engineering cyanobacteria to convert carbon dioxide to building blocks for renewable plastics

Description

The production of monomer compounds for synthesizing plastics has to date been largely restricted to the petroleum-based chemical industry and sugar-based microbial fermentation, limiting its sustainability and economic feasibility. Cyanobacteria

The production of monomer compounds for synthesizing plastics has to date been largely restricted to the petroleum-based chemical industry and sugar-based microbial fermentation, limiting its sustainability and economic feasibility. Cyanobacteria have, however, become attractive microbial factories to produce renewable fuels and chemicals directly from sunlight and CO2. To explore the feasibility of photosynthetic production of (S)- and (R)-3-hydroxybutyrate (3HB), building-block monomers for synthesizing the biodegradable plastics polyhydroxyalkanoates and precursors to fine chemicals, synthetic metabolic pathways have been constructed, characterized and optimized in the cyanobacterium Synechocystis sp. PCC 6803 (hereafter Synechocystis 6803). Both types of 3HB molecules were produced and readily secreted from Synechocystis cells without over-expression of transporters. Additional inactivation of the competing PHB biosynthesis pathway further promoted the 3HB production. Analysis of the intracellular acetyl-CoA and anion concentrations in the culture media indicated that the phosphate consumption during the photoautotrophic growth and the concomitant elevated acetyl-CoA pool acted as a key driving force for 3HB biosynthesis in Synechocystis. Fine-tuning of the gene expression levels via strategies, including tuning gene copy numbers, promoter engineering and ribosome binding site optimization, proved critical to mitigating metabolic bottlenecks and thus improving the 3HB production. One of the engineered Synechocystis strains, namely R168, was able to produce (R)-3HB to a cumulative titer of ~1600 mg/L, with a peak daily productivity of ~200 mg/L, using light and CO2 as the sole energy and carbon sources, respectively. Additionally, in order to establish a high-efficiency transformation protocol in cyanobacterium Synechocystis 6803, methyltransferase-encoding genes were cloned and expressed to pre-methylate the exogenous DNA before Synechocystis transformation. Eventually, the transformation efficiency was increased by two orders of magnitude in Synechocystis. This research has demonstrated the use of cyanobacteria as cell factories to produce 3HB directly from light and CO2, and developed new synthetic biology tools for cyanobacteria.

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Date Created
  • 2014