The news is rife with earnest chatter about climate change, "clean" or "renewable" energy, the environment and the need to rein in the burning of fossil fuels in order to stave off ecological and other crises in the coming decades.
Despite this, the United States unquestionably remains an oil- and gasoline-powered economy for the most part as the second decade of the 21st century draws to a close.
The advantages and disadvantages of alternative fuels are debated in the editorial pages of major newspapers in the United States and worldwide every day. If the Earth is really going to run out of coal, oil and gas in the years to come, what are the leading candidates for shepherding world society into a new, "alternative" energy economy? These efforts have been in progress in earnest since the early 1990s and hold a great deal of promise across multiple technological fronts.
An "Alternative" to What?
To begin with, what is a fuel? Really, it is any substance from which energy can be extracted to do useful work. Your own body uses glucose from foods as a nutrient for deriving fuel in the form of adenosine triphosphate (ATP), a molecule that powers the metabolism of every living cell.
Similarly, vehicles and other machines can be built to extract energy from the combustion of the hydrocarbons in fossil fuels, as is traditionally the case, or they can be made to rely on other chemicals and inputs.
The term "alternative fuel" was coined by the U.S. Department of Energy in the Energy Policy Act of 1992, and included biodiesel, electricity, ethanol, hydrogen, propane and fuels that were still under development, labeled emerging fuels. "Clean" technologies such as wind, solar and hydro power fall into the latter broad category.
Types of Alternative Fuels: Pros and Cons
Biodiesel: These are renewable fuels made from vegetable oils (e.g., soybean or canola oil), animal fat and even restaurant grease. As the name implies, they are for use in diesel vehicles. Unfortunately, it costs more than regular diesel fuel and can be corrosive to rubber engine parts. Biodiesel also thickens greatly in cold temperatures and burns poorly under such conditions.
Ethanol: This alcohol can be added to regular gasoline in amounts ranging from 10 percent to 83 percent or so. By 2014, nearly one hundred kinds of "flex fuel" vehicles had reached the automotive market. On the plus side, ethanol can be synthesized and does not need to be drawn from the ground or imported into the U.S. On the other hand, ethanol has less energy per unit volume, meaning that cars get lower gas mileage.
Hydrogen: This promising but extremely volatile fuel has the advantage of being ubiquitous, and its only waste product is water vapor. However, elemental hydrogen is not naturally occurring and must be produced from H-containing compounds such as methane. It is being used increasingly as a fuel source for fuel-cell vehicles.
Propane: This small, unbranched hydrocarbon, which exists in liquid form at room temperature, has been used for decades. As of 2019, only a small percentage of the propane being used in the U.S. was being used in the transportation sector.
Solar, hydro and wind: These energy sources all have the advantage of being naturally occurring and in eternal supply, and are all non-polluting. For now, they all suffer from practical constraints on their use. For example, solar cells may provide varying amounts of power that depend on factors like cloud cover. Wind speed is notoriously inconsistent, and hydro power can be both inefficient and damaging to the environment in the form of flooding.
Uses of Alternative Fuels
Alternative fuels are meant to be alternative collections of chemicals or other sources of energy. Therefore, they are used for many of the same things traditional fuels are, that is, for powering vehicles, making electricity, cooking and conducting everyday life in the modern world.
The burgeoning popularity of alternative fuels lies in both their inherent appeal (who would not want to be able to make fuel from hydrogen, or, in effect, water?) and the polluting and limited nature of fossil fuels. Regardless of how quickly these industries are progressing, they are the collective wave of the future.
- U.S. Department of Energy: Alternative Fuels Data Center: Alternative Fuels and Advanced Vehicles
- State of New Hampshire Department of Environmental Services: Alternative Fuels and Vehicles
- The California State University: Alternative Fuels: Betting on Batteries
- MIT: Spinning Science: Alternative Fuels: The Big Picture
- BBC Bitesize: Renewable Energy