Between 1906 and 2005, average global temperatures rose 1.0 to 1.7 degrees Fahrenheit in both the Northern and Southern hemispheres, according to a 2010 report by the Environmental Protection Agency (EPA). That may not seem like a significant climate shift, but once the global warming trend has started, it’s difficult -- if not impossible -- to reverse.
Some climate experts predict that the polar ice caps will recede by 40 percent by 2050. As the ice melts, it creates a feedback effect. Essentially, sunlight that would have been reflected by the ice is now absorbed by the oceans, accelerating the warming process exponentially. As temperatures rise, more water vapor will enter the atmosphere, trapping even more heat in the global greenhouse.
Carbon dioxide, the chief byproduct of fossil fuel combustion, is a potent greenhouse gas that remains in the atmosphere indefinitely. In the U.S., the burning of coal for electricity pumps more than 2.4 billion metric tons of carbon dioxide into the atmosphere every year, according to the Energy Information Administration. And that’s just electricity. What about cars? The average American passenger car spits out 11,450 pounds (5,194 kilograms) of carbon dioxide every year. There are 246 million cars in the U.S.
To cut down on carbon dioxide emissions, governments, car manufacturers and utility companies have been seriously pursuing alternative energy sources. Among the leading contenders are biofuels -- renewable, clean-burning fuels made from plant- and animal-based source materials like corn, soybeans, discarded vegetable oil or animal fat.
We hear a lot about biofuels and fossil fuels in the news, but sometimes the two terms can get tangled in our minds. Are fossil fuels really made from fossils? Can a regular car fill up on biofuels? Are there any clean-burning fossil fuels, like natural gas? Keep reading to clear up some of the confusion over biofuels and fossil fuels.
A biofuel is any fuel source that’s made from biological materials. The two most common kinds of biofuels right now are both gasoline alternatives: ethanol and biodiesel.
Ethanol is ethyl alcohol (C2H5OH). It's also known as grain alcohol because it’s often made from the distillation of grain crops like corn or soybeans. Corn is the source material for 90 percent of the ethanol produced in the U.S., but any plant material -- collectively called biomass -- can be used to make ethanol: leaves, woodchips, wild grasses, even trees. Brazil, the world’s second-largest ethanol producer, makes its biofuel from sugarcane.
When used in cars and trucks, ethanol is usually mixed with a little gasoline to improve fuel economy. The resulting fuel is called E85, denoting 85 percent ethanol and 15 percent gas. In 2007, there were 5.5 million Flex Fuel Vehicles on the road in the U.S. that could run on E85 fuel. Unfortunately, there were only 1,208 E85 filling stations -- less than 1 percent of the total filling stations in America.
What if you’re lucky enough to live near one of these ethanol stations? Does that mean you’ll get amazing fuel economy with zero emissions? Not quite. A gallon of E85 ethanol contains 80,000 BTU of energy compared with 124,800 BTU for the same amount of gasoline. That means you would have to buy 1.56 gallons of E85 for every gallon of regular gasoline. But it’s cheaper, right? Again, not quite. Technically, a gallon of E85 costs 19.9 percent less than gas, but since you’ll have to fill up more often, E85 ends up costing you more.
But the good news is that E85 is significantly friendlier to the environment. Not only is E85 clean-burning -- it produces 39 percent less carbon dioxide (CO2) than regular gasoline -- but it’s actually carbon neutral. In other words, the amount of CO2 emitted by the combustion of ethanol equals the amount of CO2 that the corn plant absorbed during its lifetime. The U.S. currently produces 9.2 billion gallons of ethanol a year and consumes 9.6 billion gallons.
Biodiesel is a biofuel made from plant- or animal-based fats and can run in a regular diesel engine. In fact, Rudolf Diesel’s original prototype engine ran on peanut oil. Biodiesel uses a chemical process called transesterification to covert fats like vegetable oil and rendered animal fats into a clean-burning, biodegradable fuel.
Biodiesel packs nearly the same energy content as regular diesel, but burns much, much cleaner. Pure biodiesel (aka B100) produces 75 percent fewer emissions than regular diesel. Purchased biodiesel is as cheap as gas, but if you can find a donated source -- like recycled fryer oil from a restaurant -- it’s potentially free!
One downside to fossil fuels is that farmland that could be used for food production is instead used to grow fuel. Another has to do with availability. For example, there are only 663 biodiesel filling stations in the U.S. and the country currently produces only 700 million gallons a year. By contrast, there are more than 160,000 gasoline filling stations in the U.S. That’s because fossil fuels -- though detrimental to the environment -- are plentiful and cheap. Read more about the pros and cons of fossil fuels on the next page.
Fossil Fuel Facts
Fossil fuels are carbon-based energy sources like coal, oil and natural gas. The story of fossil fuels begins 300 to 400 million years ago -- long before dinosaurs roamed the Earth -- when much of the planet was covered in thickly vegetated swamps and prehistoric seas. Over the millennia, the decayed remains of dead plants and sea creatures piled up on seafloors and swamp beds.
Eventually, these ancient wetlands dried up and were covered with thick sedimentary layers of sand, soil and rocks. In some cases, new seas reappeared above them. The crushing downward pressure of all of these successive layers altered the chemical composition of the plant and animal remains, creating deep deposits of carbon-rich coal, oil and natural gas. When fossil fuels are burned through combustion, they release their carbon as heat (energy) and any impurities as emissions.
Fossil fuels are called nonrenewable energy sources, since it takes hundreds of millions of years for the Earth to produce new deposits of coal, oil and natural gas. According to the World Coal Institute, there is enough coal in the ground to last us 130 more years, while there are only enough oil and natural gas reserves to last another 42 and 60 years respectively. In contrast, biofuels are considered renewable energy sources since corn, soy and other biomass can be grown indefinitely.
In the United States, 93 percent of the energy we consume comes from fossil fuels. We burn them in the form of gasoline and diesel fuel for cars, home heating oil, natural gas for cooking and heat, and coal for electricity. Americans consume fossil fuels at a remarkable rate:
- 380 million gallons (1.4 billion liters) of gasoline every day
- 1.12 billion tons (1.06 trillion kilograms) of coal every year
- 19.4 million barrels of crude oil (refined to make gasoline, diesel fuel, jet fuel, propane and plastics) every day
Fossil fuels carry a range of health and environmental risks of fossil fuels, but we use them heavily because they are cheap and abundant. The U.S. is the world’s largest producer of coal, with mines in 26 of the 50 states. That’s why over half the electricity in America is produced at coal-burning power plants. Oil is another relatively cheap and plentiful commodity. If we wanted to replace the current nonrenewable gasoline supply with a renewable biofuel like ethanol, American farmers would have to set aside 675 million acres, or 71 percent of the country’s total cropland, to grow corn exclusively for fuel.