Browsing by Subject "Biofuels"

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Algae biofuels in Texas
(2009-08) Salpekar, Ashwini; Sylvie, George; Malcolm Brown Jr., Robert
Texas – the energy center of the world – is emerging as a pioneer in algae biodiesel research and production. There are a number of reasons for this. Texas is the largest emitter of CO₂ in the country, and efforts are being made to reduce the state's dependence on fossil fuels. Also, algae – robust and promising organisms – need non-arable land, lots of sunlight and brackish/waste water, along with CO₂. Texas has all of these in abundance, plus universities and algae start-ups that are doing crucial R
Assessing the sustainability of transportation fuels : the air quality impacts of petroleum, bio and electrically powered vehicles
(2010-05) Alhajeri, Nawaf Salem; Allen, David T.; McDonald-Buller, Elena
Transportation fleet emissions have a dominant role in air quality because of their significant contribution to ozone precursor and greenhouse gas emissions. Regulatory policies have emphasized improvements in vehicle fuel economy, alternative fuel use, and engine and vehicle technologies as approaches for obtaining transportation systems that support sustainable development. This study examined the air quality impacts of the partial electrification of the transportation fleet and the use of biofuels for the Austin Metropolitan Statistical Area under a 2030 vision of regional population growth and urban development using the Comprehensive Air Quality Model with extensions (CAMx). Different strategies were considered including the use of Plug-in Hybrid Electric Vehicles (PHEVs) with nighttime charging using excess capacity from electricity generation units and the replacement of conventional petroleum fuels with different percentages of the biofuels E85 and B100 along or in combination. Comparisons between a 2030 regional vision of growth assuming a continuation of current development trends (denoted as Envision Central Texas A or ECT A) in the Austin MSA and the electrification and biofuels scenarios were evaluated using different metrics, including changes in daily maximum 1-hour and 8-hour ozone concentrations, total area, time integrated area and total daily population exposure exceeding different 1-hour ozone concentration thresholds. Changes in ozone precursor emissions and predicted carbon monoxide and aldehyde concentrations were also determined for each scenario. Maximum changes in hourly ozone concentration from the use of PHEVs ranged from -8.5 to 2.2 ppb relative to ECT A. Replacement of petroleum based fuels with E85 had a lesser effect than PHEVs on maximum daily ozone concentrations. The maximum reduction due to replacement of 100% of gasoline fuel in light and heavy duty gasoline vehicles by E85 ranged from -2.1 to 2.8 ppb. The magnitude of the effect was sensitive to the biofuel penetration level. Unlike E85, B100 negatively impacted hourly ozone concentrations relative to the 2030 ECT A case. As the replacement level of petroleum-diesel fuel with B100 in diesel vehicles increased, hourly ozone concentrations increased as well. However, changes due to the penetration of B100 were relatively smaller than those due to E85 since the gasoline fraction of the fleet is larger than the diesel fraction. Because of the reductions in NOx emissions associated with E85, the results for the biofuels combination scenario were similar to those for the E85 scenario. Also, the results showed that as the threshold ozone concentration increased, so too did the percentage reductions in total daily population exposure for the PHEV, E85, and biofuel combination scenarios relative to ECT A. The greatest reductions in population exposure under higher threshold ozone concentrations were achieved with the E85 100% and 17% PHEV with EGU controls scenarios, while the B100 scenarios resulted in greater population exposure under higher threshold ozone concentrations.
Barriers to a biofuels transition in the U.S. liquid fuels sector
(2009-12) O'Donnell, Michael Joseph; Webber, Michael E., 1971-; Allen, David T.
Demand for liquid fuels (i.e., petroleum products) has burdened the U.S. with major challenges, including national security and economic concerns stemming from rising petroleum imports; impacts of global climate change from rising emissions of CO2; and continued public health concerns from criteria and hazardous (i.e., toxic) air pollutants. Over the last decade or so, biofuels have been touted as a supply-side solution to several of these problems. Biofuels can be produced from domestic biomass feedstocks (e.g., corn, soybeans), they have the potential to reduce GHG emissions when compared to petroleum products on a lifecycle basis, and some biofuels have been shown to reduce criteria air pollutants. Today, there are numerous policy incentives—existing and proposed—aimed at supporting the biofuels industry in the U.S. However, the Renewable Fuel Standard (RFS) Program stands as perhaps the most significant mandate imposed to date to promote the use of biofuels. Overall, the RFS stands as the key driver in a transition to biofuels in the near term. By mandating annual consumption of biofuels, increasing to 36 bgy by 2022, the program has the potential to significantly alter the state of the U.S. liquid fuels sector. Fuel transitions in the transportation sector are the focus of this thesis. More specifically, the increasing consumption of biofuels in the transportation sector, as mandated by the RFS, is examined. With a well-developed, efficient, and expensive, petroleum-based infrastructure in place, many barriers must be overcome for biofuels to play a significant role in the transportation sector. Identifying and understanding the barriers to a biofuels transition is the objective of this thesis. Although fuel transitions may seem daunting and unfamiliar, the U.S. transportation sector has undergone numerous transitions in the past. Chapter 2 reviews major fuel transitions that have occurred in the U.S. liquid fuels sector over the last half century, including the phasing out of lead additives in gasoline, the transition from MTBE to ethanol as the predominant oxygenate additive in gasoline, and the recent introduction of ULSD. These historical transitions represent the uncertainty and diversity of fuel transition pathways, and illustrate the range of impacts that can occur across the fuel supply chain infrastructure. Many pertinent lessons can be derived from these historical transitions and used to identify and assess barriers facing the adoption of alternative fuels (i.e., biofuels) and to understand how such a transition might unfold. Computer models can also help to explore the implications of fuel transitions. In order to better understand the barriers associated with fuel transitions, and to identify options for overcoming these barriers, many recent research efforts have used sophisticated modeling techniques to analyze energy transitions. Chapter 3 reviews a number of these recent modeling efforts with a focus on understanding how these methodologies have been applied, or may be adapted, to analyzing a transition to biofuels. Four general categories of models are reviewed: system dynamics, complex adaptive systems, infrastructure optimization, and economic models. In chapter 4, scenarios created from a high-level model of the liquid fuels sector (the Liquid Fuels Transition model) are presented to explore potential pathways and barriers to a biofuels transition. The scenarios illustrate different pathways to meeting the requirements of the RFS mandate, and differ based on the overall demand of liquid fuels, how the biofuels mandate is met (i.e., the mix of biofuels), and the status of the ethanol blend limit in the motor gasoline sector. The scenarios are used to evaluate the infrastructure implications associated with a biofuels transition, and illustrate the uncertainty that exists in assessing such a transition.
Energy analysis of sweet sorghum ethanol using a bottom-up energy return ratio matrix approach
(2015-12) Veracruz, John A.; King, Carey Wayne, 1974-; O'Rear, Jerry; Bermann, Celio
Between 2012 and 2013 the world increased biofuel consumption by 6.1% and if forecasts hold, according to the International Energy Agency, by 2050 27% of the world’s transport energy will come from biofuels. Rather than succumb to a shortage of corn, alternative feedstocks must gain the same traction corn has gained within the ethanol production industry. When considering an alternative feedstock what must also be considered it is that energy output from ethanol production exceeds the energy needed to produce one liter of alcohol. With origins traced back to Africa, sweet sorghum, or Sorghum bicolor(L) Moench, has gained traction as a viable ethanol feedstock due to the plant’s ability to reach a harvest maturity in as little as four months. With similarities to that of sugarcane, sweet sorghum’s stalk contains a relatively balanced amount of both insoluble and soluble carbohydrates. Although sweet sorghum will flourish with the appropriate amount of water, its drought resistance provides versatility other ethanol feedstocks do not possess. However, lower inputs, drought resistance, and the ability to grow on fallow land are all meaningless if growers miss a relatively short harvesting window, or even worse, allow fermentable sugars to decay by not expediting fermentation. If sweet sorghum ethanol is to displace any amount of corn and prove its feedstock viability, its energy balance must show more energy is output than is input. By using a bottom-up matrix based approach using energy return ratios (ERRs), a product’s system may be evaluated to determine its usefulness to society. The Brandt et al. framework requires the creation of two matrices; a technology matrix, A, and an intervention matrix, B. Devising information from these matrices requires the use of three main vectors which serve as the foundation for calculating the desired ERR. Using this method in conjunction with four ERRs allows the study of energy processes used to create inputs for sweet sorghum pathways and possibly allude to how this energy is used to eliminate waste or improve efficiency through cleaner energy sources.
The energy-water nexus : an examination of the water quality impacts of biofuels
(2010-05) Twomey, Kelly Marie; Webber, Michael E., 1971-; Lawler, Desmond F.
Water and energy share an important relationship since it takes water to produce energy, and likewise, energy to pump, treat, and distribute water. This thesis explores the energy-water nexus in regards to electricity and transportation fuel production, as well as water treatment. It investigates how the Energy Independence and Security Act of 2007 might affect this interrelationship in the future since increases in corn cultivation for biofuels production are likely to lead to higher nitrate concentrations in US water reservoirs, which could trigger the requirement for additional energy consumption for drinking water treatment. The analysis indicates that advanced drinking water treatment might require an additional 2360 million kWh annually to treat drinking water currently exceeding the Environmental Protection Agency’s maximum contaminant level (MCL) limit of 10 mg per liter of nitrate-nitrogen. This is a 2100% increase in energy consumption for advanced water treatment to meet this MCL in comparison with surface water treatment alone. Although results indicate that most large surface and groundwater drinking water resources are not likely to exceed safe drinking water standards due to the expansion of corn-starch based ethanol production, smaller water reservoirs in agricultural regions are susceptible to nitrate contamination in the future. Consequently, these sources might require energy-intensive drinking water treatment to reduce nitrate levels below 10 mg per liter of nitrate-nitrogen. Based on these results, I conclude that projected increases in nitrate contamination in water may impact the energy consumed in the water treatment sector, because of the convergence of several related trends: (1) increasing cornstarch-based ethanol production, (2) increasing nutrient loading in surface water and groundwater resources as a consequence of increased corn-based ethanol production, (3) additional drinking water sources that exceed the MCL for nitrate, and (4) potentially more stringent drinking water standards for nitrate.
Extraction of Algal LIpids and their Analysis by HPLC and Mass Spectrometry
(Springer Verlag, 2012-08) Jones, J.; Manning, S.; Montoya, M.; Keller, K.; Poenie, M.
Algae are a promising source of biofuel but claims about their lipid content can be ambiguous because extraction methods vary and lipid quantitation often does not distinguish between particular lipid classes. Here we compared methods for the extraction of algal lipids and showed that 2-ethoxyethanol (2-EE) provides superior lipid recovery (>150–200 %) compared to other common extraction solvents such as chloroform:methanol or hexane. Extractions of wet and dry algal biomass showed that 2-EE was more effective at extracting lipids from wet rather than dried algal pellets. To analyze lipid content we used normal-phase HPLC with parallel quantitation by an evaporative light scattering detector and a mass spectrometer. Analysis of crude lipid extracts showed that all major lipid classes could be identified and quantified and revealed a surprisingly large amount of saturated hydrocarbons (HC). This HC fraction was isolated from extracts of bioreactor-grown algae and further analyzed by HPLC/MS, NMR, and GC/MS. The results showed that the sample consisted of a mixture of saturated, straight- and branched-chain HC of different chain lengths. These algal HC could represent an alternative biofuel to triacylglycerols (TAG) that could feed directly into the current petroleum infrastructure.
Hydrologic impacts of biofuel expansion in the Ivinhema basin, Brazil
(2015-05) Libra, Jesse Madden; King, Carey Wayne, 1974-; McKinney, Daene
Brazil produces approximately a quarter of the world's yearly ethanol demand, making it a global leader in biofuel production. The repercussions for local water resources in areas of intensive biofuel expansion, however, remain uncertain. The purpose of this study is to assess the effects of various land-use scenarios on water sustainability in Brazil, specifically the Ivinhema basin. This basin, located in Southern Mato Grosso do Sul, has experienced extensive sugarcane expansion since the mid-1990s – a trend that is expected to continue in the short to medium term. To achieve the goals of the study, I used the Stockholm Environment Institutes' Water Evaluation and Planning software (WEAP), specifically, the Soil Moisture Method, to model hydrologic processes in the Ivinhema basin from 1990-2013. The study has two parts. The first part focuses on model calibration in a data poor environment. To circumvent poor data quality, I examined the effects on model accuracy of a number data processing methods for land-use, precipitation, and ethanol production data. A total of 8 different calibration scenarios were run using these different data inputs, which I evaluated for accuracy using Nash-Sutcliffe Model Efficiency coefficients. Those producing the best results were used as a baseline for part two. The second part of the study uses the baseline model developed in part one to investigate the crop yield and stream flow effects under three different irrigation and ethanol production scenarios. Water consumption for the ethanol production process has little impact on stream flows, with daily demand peaking at 0.7 percent of baseline flows. Irrigation, however, massively reduces flows -- when irrigation is limited to only sugarcane, flow reductions of over 60 percent only occurs on 1.98 percent of days, while reductions of up to 100 percent during the dry season. Despite these large flow reductions, sugarcane yield increase from irrigation was only 7-14 percent over the study period.
An integrated resource and biological growth model for estimating algal biomass production with geographic resolution
(2010-12) Wogan, David Michael; Da Silva, Alexandre K., 1975-; Webber, Michael E., 1971-
This thesis describes a geographically- and temporally-resolved, integrated biological and engineering model that estimates algal biomass and lipid production under resource-limited conditions with hourly and county resolution. Four primary resources are considered in this model: sunlight, carbon dioxide, water, and land. The variation in quantity and distribution of these resources affects algae growth, and is integrated into the analysis using a Monod model of algae growth, solar insolation data, and published values for water, carbon dioxide, and land availability. Finally, lipid production is calculated by assuming oil content based on dry weight of the biomass. The model accommodates a range of growth and production scenarios, including water recycling, co-location with wastewater treatment plants and coal-fired generators, and photobioreactor type (open pond or tubular), among others. Results for every county in Texas indicate that between 86 million and 2.2 billion gallons of lipids per year can be produced statewide for the various growth scenarios. The analysis suggests that algal biomass and lipid production does indeed vary geographically and temporally across Texas. Overall, most counties are water-limited for algae production, not sunlight or carbon dioxide-limited. However, there are many nuances in biomass and lipid production by county. Counties in west Texas are typically not solar- or land-limited, but are constrained by either water or carbon dioxide resources. Consequently, counties in east Texas are limited by either water, or land (depending on the fraction of water recycling). Varying carbon dioxide concentration results in higher growth rates, but not always increased biomass and lipid production because of limitations of other resources in each county.
Mitigation of municipal biosolids via conversion to biocrude oil using hydrothermal liquefaction : a techno-economic analysis
(2015-05) Bond, Cody Ray; Berberoglu, Halil; Greene, David
In this techno-economic analysis, we have shown that hydrothermal liquefaction (HTL) technology can be integrated with existing biosolids management facilities that utilize anaerobic digestion and biogas capture. The overall process converts raw sewage sludge to refinery-ready biocrude oil. The Hornsby Bend Biosolids Management Plant (HBBMP) in Austin, TX is used as a case study. First, the operation of the plant without any modification was modeled and validated with field data. A standalone HTL processing unit was then considered as an add-on to the existing infrastructure. Technical and economic parameters were obtained from literature and experimental data. The results showed that savings of about $32 M over current operation with a payback period of 4.35 years were achievable at HBBMP. A nation-wide implementation could result in production of almost 4.5 million barrels of upgraded biocrude oil per year while offsetting about 330,000 metric tons of CO2 equivalent greenhouse gas emissions annually.
Radiant and thermal energy transport in planktonic and benthic algae systems for sustainable biofuel production
(2011-05) Murphy, Thomas Eugene; Berberoglu, Halil; Howell, John R.
Biofuel production from microalgal biomass offers a clean and sustainable liquid fuel alternative to fossil fuels. In addition, algae cultivation is advantageous over traditional biofuel feedstocks as (i) it does not compete with food production, (ii) it potentially has a much greater areal productivity, (iii) it does not require arable land, and (iv) it can use marginal sources of water not suitable for irrigation or drinking. However, current algae cultivation technologies suffer from (i) low solar energy conversion effiencies, (ii) large thermal fluctuations which negatively affect the productivity, and (iii) large evaporative losses which make the process highly water intensive. This thesis reports a numerical study that address these key issues of planktonic as well as benthic algal photobioreactor technologies. First, radiant energy transfer in planktonic algal photobioreactors containing cells with different levels of pigmentation was studied. Chlamydomonas reinhardtii and its truncated chlorophyll antenna transformant tla1 were used as model organisms. Based on these simulations guidelines are derived for scaling the size and microorganism concentration of photobioreactors cultivating cells with different levels of pigmentation to achieve maximum photosynthetic productivity. To achieve this, the local irradiance obtained from the solution of the radiative transport equation (RTE) was coupled with the specific photosynthetic rates of the microorganisms to predict both the local and total photosynthetic rates in a photobioreactor. For irradiances less than 50 W/m2, the use of genetically modified strains with reduced pigmentation was shown to have negligible effect on increasing photobioreactor productivity. However, at irradiances up to 1000 W/m2, improvements of up to 30% were possible with cells having 63% less pigment concentration. It was determined that the ability of tla1 to transmit light deeper into the photobioreactor was the primary mechanism by which a photobioreactor using the modified strain can achieve greater productivity. Furthermore, it was determined photobioreactors using each strain have dead zones in which the local photosynthetic rate is negligible due to nearly complete light attenuation. These dead zones occur at local optical thicknesses greater than 169 and 275 in photobioreactors using the wild strain and the genetically modified strain, respectively. In addition, a thermal model of an algae biofilm photobioreactor was developed to assess the thermal fluctuations and evaporative loss rate of these novel photobioreactors under varying outdoor conditions. The model took into account air temperature, irradiance, relative humidity, and wind speed as inputs and computed the temperature and evaporative loss rate as a function of time and location in the photobioreactor. The model was run for a week-long period in each season using weather data from Memphis, TN. The range of the daily algae temperature variation was observed to be 13.2C, 12.4C, 12.8C, and 9.4C in the spring, summer, winter, and fall, respectively. Furthermore, without active cooling, the characteristic evaporative water loss from the system is approximately 6.3 L/m2-day, 7.0 L/m2-day, 4.9 L/m2-day, and 1.5 L/m2-day in the spring, summer, fall, and winter, respectively.
Teaching life cycle assessment using biofuels to develop process thinking and strengthen core science understanding
(2011-08) Moyers, Audrea Haynes; Allen, David T.; Crawford, Richard H.
This action research project focuses on teaching life cycle assessment to engineering students in high school, using biofuels as a relevant application. The study examined the effectiveness of teaching methods related to both the engineering content—life cycle assessment—and the science content—biofuel production. It also examined underlying conceptions that students have about the preferability of some common consumer products from an environmental perspective, as well as their knowledge of ethanol compared to gasoline. The participants in the study consisted of sixteen college students enrolled in an Engineering Energy Systems course while pursuing either an undergraduate or graduate degree related to teaching engineering and science at the secondary level. The students participated in lessons written for a high school engineering science course currently under development in the UTeach Engineering program at The University of Texas at Austin. Data were collected from a pre- and post-unit assessment, observation of student activities and behaviors, and a participant survey. The results of the study suggest that student understanding of the environmental implications of products or processes is deeper after completion of the unit. The study also shows a positive relationship between hands-on sense-building activities and student engagement. As an action research project, the primary goal is the immediate improvement of teaching to increase learning in the classroom. Modifications to the unit and lesson design have been made based on the results of the study in preparation for using the unit with high school students in the following school year.