Factors Influencing the Green House Gas Footprint of US Dairy Farms

Environmental Economics and Policy, Livestock Production/Industries,

An Improved Spectrophotometric Method To Study the Transport, Attachment, and Breakthrough of Bacteria through Porous Media

This study reports an improved spectrophotometric method for studying bacterial (Pseudomonas fluorescens UPER-1) transport and attachment in saturated porous media (silica sand). While studying the effect of ionic strength by the traditional packed-column spectrophotometric method, we encountered an artifact. The absorbance of a well-stirred bacterial suspension was found to decrease with time in the presence of high concentrations of sodium and potassium phosphate salts (≥10(−2) M) as the cells continued to age in a resting stage. Our results show that collision efficiency and a bed ripening index will be in error by as much as 20% if breakthrough is measured by the traditional spectrophotometric technique. We present an improved experimental technique that will minimize the artifact and should substantially advance the understanding of bacteria transport in porous media

Modeling the effects of systematic variation in ionic strength on the attachment kinetics of Pseudomonas fluorescens UPER-1 in saturated sand columns

We report the effects of salt type and concentration on the change in attachment kinetics when bacteria are pumped through a column of water-saturated clean sand over relatively long periods of time (up to 35 pore volumes). The species Pseudomonas fluorescens UPER-1 was found to exhibit three different kinds of attachment kinetics: first order, second order, and an intermediate order. The attachment kinetics of bacteria was modeled by using the advection-dispersion equation coupled with a set of equations for each kind of attachment kinetics while using colloid filtration theory to predict collector efficiencies. At lowor zero salt concentrations (≤10-4 M) a second-order kinetics model (\u27blocking\u27), a \u27first-order\u27 kinetics model, and an intermediate-order kinetics model (\u27ripening\u27), were all found to fit the data equally well. At intermediate and high salt concentrations (≥10-3 M) the ripening model was found to fit the data best. We report values for collision efficiencies of bacteria in the range 0.01-0.2, depending upon the salt type and concentration. This study points out the importance of long-term experiments to study the effect of ionic strength on bacteria attachment kinetics in saturated porous media and the phenomenon of cell-to-cell attachment at high ionic strength. This study further points out the range of kinetics to expect when bacteria attach to natural porous media and suggests a modeling framework

Life cycle analysis of silane recycling in amorphous silicon-based solar photovoltaic manufacturing

Amorphous silicon (a-Si:H)-based solar cells have the lowest ecological impact of photovoltaic (PV) materials. In order to continue to improve the environmental performance of PV manufacturing using proposed industrial symbiosis techniques, this paper performs a life cycle analysis (LCA) on both conventional 1-GW scaled a-Si:H-based single junction and a-Si:H/ microcrystalline-Si:H tandem cell solar PV manufacturing plants and such plants coupled to silane recycling plants. Both the energy consumed and greenhouse gas emissions are tracked in the LCA, then silane gas is reused in the manufacturing process rather than standard waste combustion. Using a recycling process that results in a silane loss of only 17% instead of conventional processing that loses 85% silane, results in an energy savings of 81,700 GJ and prevents 4400 tons of CO2 from being released into the atmosphere per year for the single junction plant. Due to the increased use of silane for the relatively thick microcrystalline-Si:H layers in the tandem junction plants, the savings are even more substantial-290,000 GJ of energy savings and 15.6 million kg of CO2 eq. emission reductions per year. This recycling process reduces the cost of raw silane by 68%, or approximately $22.6 million per year for a 1-GW a-Si:H-based PV production facility and over$79 million per year for tandem manufacturing. The results are discussed and conclusions are drawn about the technical feasibility and environmental benefits of silane recycling in an eco-industrial park centered around a-Si:H-based PV manufacturing plants. © 2012 Elsevier B.V

An inversion algorithm for determining area-source emissions from downwind concentration measurements

Measuring emissions from nonuniform area sources, such as waste repository sites, has been a difficult problem. A simple but reliable method is not available. An objective method of inverting downwind concentration measurements, utilizing an assumed form of atmospheric dispersion to reconstruct total emission rate and distribution, is described in this study. The Gaussian dispersion model is compared to a more realistic model based on K-theory and similarity expressions. A sensitivity analysis is presented indicating the atmospheric conditions under which a successful application of the method could be anticipated. Field releases of sulfur hexafluoride (SF6) from a simulated area source in flat terrain were conducted to check the method, ability to reconstruct source distribution, and total emission rate. The sensitivity analysis and the field study confirm that a few ground-level concentration measurements and a simple determination of the atmospheric dispersion characteristics are sufficient, under neutral to stable conditions, to obtain the total emission rate accurately. Reconstruction of the spatial pattern of the source is possible by utilizing concentration information from samplers located on two separate ground-level receptor lines, if a shift in the wind direction occurs and if it can be assumed that the total emission rate is time invariant. A method of cross-checking the accuracy of the reconstruction, using a simultaneous tracer release, is presented

Design guidance for chemical processes using environmental and economic assessments

Traditionally, process design is focused on the selection of process technologies and optimization of chemical processes based on economic considerations. Increasingly, there is a need to broaden the scope of process design by including environmental impacts. To successfully optimize a process, multiple objective functions must be chosen to consider a variety of economic and environmental process attributes. The objective of this paper is to provide design procedures and guidance for optimizing chemical processes simultaneously based on economic and environmental aspects. Two chemical processes are studied, including a process to recover/recycle VOCs (volatile organic chemicals) from a gaseous waste stream and optimum heat-exchanger network design

Chapter 6 - Low-Carbon Aviation Fuel Through the Alcohol to Jet Pathway

The aviation industry is seeking economical and technically viable approaches to providing sustainable alternatives to petroleum-based jet fuel. For example, the Federal Aviation Administration (FAA) Destination 2025 (FAA 2025) has a goal to develop cleaner jet fuels, explore new ways to meet environmental and energy goals, and foster development towards one billion gallons of renewable jet fuel for aviation use by 2018. Alternative jet fuels via Fischer–Tropsch (F–T) and hydrotreated vegetable oils (HEFA) have already been approved for use in jet fuel blends of up to 50%. Other conversion processes, such as alcohol to jet (ATJ), are in various stages of development. This chapter focuses on opportunities for production of jet fuel blend components through an ethanol intermediate via a number of processing routes. These are then compared to conversion routes through other oxygenated intermediates, such as higher alcohols (eg, butanol). Higher alcohols provide technically simple conversion chemistry routes to jet blend components, but are currently produced in small quantities (relative to fuels) for the chemical market. Ethanol on the other hand is widely produced as both a fuel and a chemical and has an established distribution infrastructure. Furthermore, renewable ethanol volumetric yields via fermentation surpass those of higher alcohols. Ethanol conversion processes can produce both paraffinic and cyclic molecules. However, the conversion pathway from ethanol through ethylene is more challenging than from higher alcohol-derived olefins. Mixed oxygenated intermediates can also belong in the ATJ category, but are not yet at the same stage of development as alcohols. The major market drivers for producing alternative jet fuel components, including ATJ, are climate change, cost stability, and national security. Biologically derived ATJ fuels can provide significant climate change benefits by reducing CO2 life cycle emissions, possibly exceeding 80%. In addition, they produce lower levels of sulphur oxides and particulate matter. Because jet fuel accounts for 40% of an airline’s operating costs, reducing price fluctuations associated with petroleum is another significant driver. Finally, dependence on foreign oil could be minimized using alternative fuels. As a result of these drivers, government agencies as well as the private sector have set aggressive targets to increase their consumption of alternative fuels. In addition to targets, the government has provided favourable policies to incentivize alternative aviation fuel use. Carbon taxes abroad and potentially in the United States will drive up prices of petroleum-based fuels, making alternative fuels more competitive. Government incentives in the form of renewable fuel credits are expected to further improve alternative fuel viability. Energy Information Agency (EIA) projections suggest there may be a significant surplus of ethanol over that required for gasoline blending, potentially filling 4% of jet fuel demand in 2020. EIA projections also suggest there is a positive price differential between ethanol intermediate and jet fuel in future scenario projections, unless oil prices drop to the Low Oil Case. Ethanol currently has a price and market share advantage over other alcohols, such as butanol. However, development of ethanol to jet technology lags butanol to jet technology. Reported production costs for raw ethanol, projected ethanol supplies over that needed for gasoline blending, and the presence of existing infrastructure all suggest that ethanol is a viable intermediate for the production of alternative jet fuel components

An Education Program in Support of a Sustainable Future

The historical evolution and current status of sustainability education at Michigan Technological University is described. The history considers the last 15 years, during which, the faculty of Michigan Tech have been collaborating on the development of environmental curricula and courses. This development effort initially focused on specialized offerings for the environmental/chemical engineering programs. With time, recognition of the importance of environmental issues (wastes, natural resources, energy, etc.) to other disciplines across the campus grew. For example, chemists, biologists, foresters, etc. each have a role in characterizing the behavior of ecological systems. Engineering disciplines that are focused on the design of products, processes, or systems influence long term societal sustainability. Social scientists must understand the relationships/linkages between the environment, industry, citizens, and government. Greener products, environmentally responsible processes, life cycle thinking, and environmental stewardship need to become part of the modern lexicon of globally aware students. Faculty from diverse disciplines across the campus are now collaborating to develop courses and modify curricula to educate students with respect to the triple bottom line (i.e., sustainable economic, societal, and environmental future). Problems associated with the traditional education paradigm are discussed. A new education model aimed at training students to create a sustainable future is proposed