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Definitions of Alternative Fuels | Resources

Alternative Fuels Strategies

An alternative fuel, most generally defined, is any fuel other than the traditional selections, gasoline and diesel, used to produce energy or power. The emissions impact and energy output provided by alternative fuels varies, depending on the fuel source. Examples of alternative fuels include biodiesel, ethanol, electricity, propane, compressed natural gas, and hydrogen.

Definitions of Alternative Fuels

Alternative fuels being used in transportation are briefly described below.

Biodiesel is a clean burning, renewable alternative fuel that can be produced from a wide range of vegetable oils and animal fats. Biodiesel contains no petroleum, but can be blended at any level with petroleum diesel to create a biodiesel blend. It can be used in compression-ignition (diesel) engines with little or no modifications.

Ethanol is a renewable alternative biofuel made from various plant materials. Ethanol can be blended with gasoline in varying quantities; most spark-ignited gasoline-style engines will operate well with mixtures of 10 percent ethanol (E10). E85, a mixture of 85 percent ethanol and 15 percent unleaded gasoline, is an alternative fuel for use in flexible fuel vehicles (FFVs).

Electricity used to power vehicles is provided by the electricity grid and stored in the vehicle's batteries. Vehicles that run on electricity have no tailpipe emissions. Electric vehicles are not currently available from the major auto manufacturers; most electric vehicles have been converted by amateur mechanics.

Propane, also known as liquefied petroleum gas, is a by-product of natural gas processing and crude oil refining. Propane is less toxic than other fuels. It has a high octane rating and excellent properties for spark-ignited internal combustion engines. Currently, less than 2 percent of U.S. propane consumption is used for transportation; however, interest is growing due to its domestic availability, high energy density, and clean-burning qualities.

Compressed Natural Gas (CNG) is a natural gas that is extracted from wells and compressed. Natural gas is a fossil fuel comprised mostly of methane and is cleaner burning than gasoline or diesel fuel. Natural gas vehicles have been found to produce less greenhouse gas emissions than gasoline vehicles, but very little natural gas consumption is currently used for transportation fuel.

Hydrogen (H2) is a renewable, domestically-produced, alternative fuel that can be used to create electricity. A chemical reaction between oxygen and hydrogen produces the electric power, and when the transportation fuel is pure hydrogen, the only resulting emission is water vapor. Depending on the energy source that causes the chemical reaction, hydrogen can be an emission-free transportation fuel. Not widely used today, current government and industry research and development are investigating safe and economical hydrogen production and hydrogen vehicles.


Alternative Fuels & Advanced Vehicles Data Center
U.S. Department of Energy
This site is a comprehensive clearinghouse of data, publications, tools, and information related to advanced transportation technologies. The AFDC holds more than 3,000 documents, interactive tools that help fleets and consumers make transportation decisions, and a wealth of information to educate the public on alternative fuels and advanced vehicles. The AFDC focuses not only on alternative fuels, but all advanced transportation fuels, vehicles, and technologies.
Assessment of the Greenhouse Gas Emission Benefits of Heavy Duty Natural Gas Vehicles in the United States (2005) (PDF 495kb)
The U.S. Department of Transportation, Center for Climate Change & Environmental Forecasting
This paper presents a review of existing literature on emission factors, emission data collection techniques, and analytic approaches; presents the results of SAIC's analysis of available CO2 and CH4 GHG emission data from chassis dynamometer tests of heavy-duty vehicle exhaust; and provides suggestions for further reducing this uncertainty. The research focused on emissions data from diesel-, LNG-, and CNG-fueled heavy-duty vehicles.
Biofuels - An Important Part of a Low-Carbon Diet (2007) (PDF 932kb)
Union of Concerned Scientists
This report is to ensure that we "count carbs" accurately, by explaining why we need a comprehensive accounting system for carbon emissions--one that measures global warming emissions over a transportation fuel's entire life cycle. We also need to "make carbs count" by creating performance-based policies that will reward low-carbon transportation fuels for their performance.
Biofuels for Transport: Policies and Possibilities (2007) (PDF 232kb)
Organization for Economic Co-operation and Development
This Policy Brief looks at the current situation with biofuels in road transport, and how governments can balance all these elements when crafting policies for energy and biofuels.
Biofuels for Transportation: A Climate Perspective (2008) (PDF 403KB)
Pew Center on Global Climate Change
This paper presents the role of biofuels and their climate impacts. It offers an introduction to the current state of play for biofuels: the technologies used in their production, their greenhouse gas (GHG) emissions, and associated policy issues.
California State Alternative Fuels Plan (2007) (PDF 1.9MB)
California Energy Commission, California Air Resources Board
The California State Alternative Fuels Plan presents strategies and actions California must take to increase the use of alternative non-petroleum fuels in a manner that minimizes costs to the state and maximizes the economic benefits of in-state production. The plan assessed various alternative fuels and developed fuel portfolios to meet California's goals to reduce petroleum consumption, increase alternative fuels use, reduce greenhouse gas emissions and increase in-state production of biofuels, without causing a significant degradation of public health and environmental quality. The key circumstances and conditions necessary to achieve the plan outcomes are presented for each fuel based on plan assumptions and analysis. The plan describes a 2050 Vision that extends the plan outcomes beyond the milestone years of 2012, 2017, and 2022 and lays a foundation for building a multi-fuel transportation energy future for California.
Changes Needed to Enable Use of Hydrogen as Alternative Fuel in Commercial Motor Vehicles (2009)
Transportation Research Board
This paper provides a brief overview the results of a two-year project undertaken to ascertain changes needed for the U.S. Department of Transportation (DOT) to enable the use of hydrogen as an alternative fuels in commercial motor vehicles. At present, there are no general guidelines to assist commercial motor vehicle fleet managers who are considering hydrogen as an alternative fuel. Thus, the primary purpose of DOT's two-year project was to compile general guidelines in lay language on the proper operation, maintenance, and inspection of hydrogen fuel systems in commercial motor vehicles (i.e., trucks and motorcoaches).
Changes to Consider in the Federal Motor Carrier Safety Regulations and North American Standard Inspection Procedures to Accommodate Hydrogen as an Alternative Fuel (2007) (PDF 97kb)
Booz Allen Hamilton; Federal Motor Carrier Safety Administration
This reports reviews the existing Federal Motor Carrier Safety Regulations that pertain to fueling systems to determine if changes to those regulations are necessary to accommodate the introduction of gaseous and liquid hydrogen as alternative fuel in commercial vehicles. These types of fuels have unique physical and chemicals properties that are different from traditional automotive fuels and have specific hazards associated with them.
Clearing the Air with Ethanol - A review of the real world impact from fuels blended with ethanol (2006) (PDF 1.91mb)
Better Environmental Solutions and Renewable Energy Action Project
This report reviews several case studies to address concerns about ethanol and ethanol blends increasing ozone pollution.
Climate Sensitive Transportation Management: Evaluating Alternative Goals for Traffic Growth (2009)
Transportation Research Board 88th Annual Meeting
This paper illustrates a methodology to evaluate alternative national traffic growth goals against greenhouse gas reduction goals, considering motor vehicle fleet characteristics and fuel policies. Several alternative scenarios are evaluated, ranging from historic trends to a "Climate Sensitive Transportation Management" (CSTM) policy that would seek to stabilize U.S. vehicle miles traveled (VMT) at projected 2010 levels through 2050.
Department of Energy Announces Up to $15.3 Million for Long-Term Hydrogen Vehicle Development (2008)
U.S. Department of Energy
This article reports on the selection of 10 cost-shared hydrogen storage research and development projects as part of President Bush's Hydrogen Fuel Initiative for research and development for hydrogen-powered fuel cells.
Drilling, Alternative Fuels and Efficiency: Can the United States Wean Itself From Imported Oil? (April 2009)
Philip Fairey, Energy Policy, Volume 37, Issue 4
This article presents the historical facts relative to America's oil demand and domestic and world oil production resources. These historical trends are used to construct a scenario of future supply and demand for oil in the US. A range of existing technologies, which can reduce the need for petroleum imports, are then evaluated using wedges analysis, giving projections to the year 2030.
Economic and Environmental Transportation Effects of Large-Scale Ethanol Production and Distribution in the United States (April 2009) (PDF 186kb)
Environmental Science & Technology, Vol. 43 Issue 7, American Chemical Society
The combination of current and planned 2007 U.S. ethanol production capacity is 50 billion L/yr, one-third of the Energy Independence and Security Act of 2007 (EISA) target of 136 billion L of biofuels by 2022. In this study, we evaluate transportation impacts and infrastructure requirements for the use of E85 (85% ethanol, 15% gasoline) in light-duty vehicles using a combination of corn and cellulosic ethanol. Ethanol distribution is modeled using a linear optimization model. Estimated average delivered ethanol costs, in 2005 dollars, range from $0.29 to $0.62 per liter ($1.3−2.8 per gallon), depending on transportation distance and mode. Emissions from ethanol transport estimated in this work are up to 2 times those in previous ethanol LCA studies and thus lead to larger total life cycle effects. Long-distance transport of ethanol to the end user can negate ethanol's potential economic and environmental benefits relative to gasoline. To reduce costs, we recommend regional concentration of E85 blends for future ethanol production and use.
Energy Efficiency - Transportation
U.S. Department of Energy
This federal agency website presents several programs and initiatives offered by DOE to support the development of alternative fuels and the infrastructure to support their commercialization.
Ethanol: A Convenient Solution to the Inconvenient Truth (2007) (PDF 7.27mb)
Better Environmental Solutions
This report is an analysis to show how ethanol blends can reduce air pollution, improve mileage, and save drivers money.
U.S. Department of Energy and U.S. Environmental Protection Agency
This website provides information for U.S. consumers interested in the different types of alternative fuels and advanced vehicles, such as hybrids and flex-fuel vehicles. There is also information on advanced technologies.
Fuels Resources
U.S. Environmental Protection Agency
This webpage provides fact sheets about alternative vehicle technologies and fuels, including a fact sheet about biodiesel and its performance, availability, affordability, and benefits.
Fuel Options for Reducing Greenhouse Gas Emissions from Motor Vehicles (2003) (PDF 1.2mb)
U.S. Department of Transportation, Center for Climate Change and Environmental Forecasting
This report assess the potential of gasoline substitutes to reduce emissions of carbon dioxide and other greenhouse gases by automobiles and light-duty trucks. Reductions in future GHG emissions are estimated under specific assumptions about growth in light-duty vehicle travel and the replacement of gasoline by various other fuels, both in the near term (10 years) and over the longer term (25 years).
Getting More Miles Per Gallon (2009)
Evans, Christopher and Cheah, Lynette and Bandivadekar, Anup and Heywood, John. Issues in Science and Technology, Vol. 25 No. 2
Corporate Average Fuel Economy (CAFE) standards were increased by Congress in December 2007, the first time in more than two decades, due to concerns over human-induced climate change and energy security. In order to induce drivers to change their driving habits, however, other consumer oriented policy options may need to be implemented in addition to CAFE standards. The authors argue that vehicle fuel economy may be improved through three primary methods: reducing vehicle weight and size; increased market share of alternative powertrains that show more efficiency than conventional gasoline engines; and, rather than continuing the historical trend of emphasis on vehicles that are heavier, larger, and more powerful, ensuring that improvements in vehicle technology's efficiency gains are directed toward increasing fuel economy.
Greener Fuels, Greener Vehicles: A State Resource Guide (2008) (PDF 740kb)
National Governors Association
This is a best practices State Resource Guide that discusses the alternative fuels and vehicles available today and the advanced technologies that will be available in the future. This guide reviews the alternative fuels and technologies currently available, examines ways for the government to promote greener transportation, and provides an overview of the core barriers to wider consumption of these new options, all in an effort to help the United States to reduce its reliance on petroleum, lower GHG emissions, and secure a clean energy future.
Hydrogen & Fuel Cells: Advances in Transportation and Power (2009)
Michael F. Hordeski, Fairmont Press
This book discussess the challenges and necessity of building a hydrogren infrastructure.
Hydrogen Applications for Lamber-St. Louis International Airport (PDF 803kb)
Mathew Thomas, Missouri University of Science and Technology (Dissertation)
Today, major airports are facing challenges related to pollution, energy efficiency, and safety and security. Hydrogen and fuel cell technologies, regarded as one of the key energy solutions of the 21st century are more energy efficient and reliable than conventional systems and have the potential to diminish these challenges. These technologies can also play a significant role in reducing the noise, air, and water pollution and enhancing energy security. This paper presents the design of a set of hydrogen technologies and systems that are commercially available and are ready for practical, real-world use.
Industrial Gas Turbine Combustion Performance Test of DME to use as an Alternative Fuel for Power Generation (April 2009)
Min Chul Lee, Seok Bin Seo, Jae Hwa Chung, Yong Jin Joo, Dal Hong Ahn, Fuel, Volume 88, Issue 4
This study was conducted to verify whether DME is a good fuel for gas turbines and to identify potential problems in fuelling a commercial gas turbine with DME. In this study, the GE7EA gas turbine of the Pyong-tak power plant in Korea was selected as the target of DME application. Combustion performance tests were conducted by comparing DME with methane, which is a major component of natural gas.
Life Cycle Cost Analysis to Examine the Economical Feasibility of Hydrogen as an Alternative Fuel (April 2009)
Ji-Yong Lee, Moosang Yoo, Kyounghoon Cha, Tae Won Lim, Tak Hur, International Journal of Hydrogen Energy
This study uses a life cycle costing (LCC) methodology to identify when hydrogen can become economically feasible compared to the conventional fuels and which energy policy is the most effective at fostering the penetration of hydrogen in the competitive fuel market. The target hydrogen pathways in this study are H2 via natural gas steam reforming (NG SR), H2 via naphtha steam reforming (Naphtha SR), H2 via liquefied petroleum gas steam reforming (LPG SR), and H2 via water electrolysis (WE). In addition, the conventional fuels (gasoline, diesel) are also included for the comparison with the H2 pathways..
Light-Duty Vehicle Fuel Economy, Energy Use, and CO2 Global Trends and Opportunities (2009)
Fulton, Lewis M; Cazzola, Pierpaolo. Transportation Research Board 88th Annual Meeting
This paper provides an overview of recent trends in light-duty vehicle fuel economy around the world, new projections, and a discussion of fuel economy technology opportunities and costs over the next 30-50 years - all in the context of recent IEA projections of global energy use (especially oil use) and CO2 emissions.
Liquid Transportation Fuels from Coal and Biomass: Technological Status, Costs, and Environmental Impacts
The National Academy of Sciences
Liquid Transportation Fuels from Coal and Biomass provides a snapshot of the potential costs of liquid fuels from biomass by biochemical conversion and from biomass and coal by thermochemical conversion. Policy makers, investors, leaders in industry, the transportation sector, and others with a concern for the environment, economy, and energy security will look to this book as a roadmap to independence from foreign oil. With immediate action and sustained effort, alternative liquid fuels can be available in the 2020 time frame, if or when the nation needs them.
Natural Gas and Liquefied Natural Gas for Transportation In California
California Energy Commission
This fact sheet provides an overview of compressed natural gas as a vehicle fuel, as well as its benefits and details of compressed natural gas usage in the State of California.
Optimal Ethanol Blend-Level Investigation (2007) (PDF 1.0mb)
American Coalition for Ethanol
This report documents the findings of the vehicle fuel economy and emissions testing on four 2007 model vehicles. The purpose was to investigate the possible existence of a fuel economy-based optimal ethanol blend level and to acquire hot-start tailpipe emissions.
Plants at the Pump: Biofuels, Climate Change, and Sustainability (2008) (PDF 2.5mb)
World Resources Institute
This report addresses the role that transport fuels play in the climate change discussion .The authors analyze the technology of biofuels, the policy structures that drive biofuels technologies, and the drivers for investment and conclude that a shift to biofuels is possible, but will only succeed if standards and incentives are put into place to reward improved carbon and energy performance and promote sustainability.
The Role of a Low Carbon Fuel Standard in Reducing Greenhouse Gas Emissions and Protecting Our Economy (2007)
Office of the Governor, California
This White Paper discusses the expected benefits of an Executive Order that would establish a Low Carbon Fuel Standard (LCFS) for transportation fuels sold in California, and an initial LCFS goal of reducing the carbon intensity of California's passenger vehicle fuels by at least 10 percent by 2020.
The Role of Biofuels for Transportation in CO2 Emission Reduction Scenarios with Global Versus Regional Carbon Caps (March 2009)
Maria Grahn, Christian Azar, Kristian Lindgren, Biomass and Bioenergy, Volume 33, Issue 3
This study analyzes how international climate regimes affect cost-efficiency of fuel choices in the transportation sector. The analysis is carried out with a regionalized version of the Global Energy Transition model, GET-R 6.0. Two different carbon dioxide (CO2) reduction scenarios are applied, both meeting an atmospheric CO2 concentration target of 450 ppm by the year 2100.
Smart Choices for Biofuels (2009) (PDF 948kb)
Jane Earley and Alice McKeown, WorldWatch Institute
This report argues that over the next decade and beyond, U.S. national, state, and local policy must focus on developing sustainable biofuels—rather than just more biofuels—that can play a role in the emerging new energy economy. These fuels should be seen as part of an expanded renewable energy portfolio that emphasizes greater fuel efficiency and reduced demand as well as the development of new sustainable energy technologies that may one day go beyond biofuels.
Use of U.S. Croplands for Biofuels Increase Greenhouse Gases Through Emissions from Land-Use Change (2008)
Science Magazine
This study examines how substituting biofuels for gasoline may increase greenhouse gas emissions as farmers worldwide respond to higher prices and convert forest and grassland to new cropland to replace the grain or cropland diverted to biofuels.

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