Researchers from the U.S. Department of Agriculture (USDA) gained a bit of attention in July 2010 when they released a paper describing how they
converted ordinary butter into usable biofuel. In addition to the unlikely
source material, the process was notable because it sped up some energy-laden steps -- namely harvesting milk and converting it
into butter.
This may not sound particularly remarkable, but efficient development of biofuels still eludes scientists.
For one thing, there's the particularly ticklish matter of net energy yield. If the energy input is more than the output, the energy source is useless. Consider using two gallons (7.57 liters) of gasoline to produce one gallon (3.79 liters) of gasoline. You'd have a net energy yield of negative one: useless.
Improving the net energy yield is key if researchers are ever going to fulfill the United States' goal of producing 36 billion gallons (136 trillion liters) of biofuel by 2022.
Producing Biofuel Emits CO2
Even more problematic is the fact the energy used to produce biofuels tends to come in the form of fossil fuels. So scientists emit carbon dioxide even they work to produce a fuel that doesn't.
"This makes most liquid fuels, as they are produced at present, decidedly un-'carbon neutral'," says civil and environmental engineering professor Lisa Colosi. She researches the use of algae as a source material, or feedstock, for biodiesel at the University of Virginia.
Those last two words -- carbon neutral -- are vital. The more carbon dioxide emissions that are emitted in order to create an environmentally friendly energy source, the less useful that new energy source is.
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Some kinds of agricultural feedstock, like soybeans and corn, are particularly far from being carbon-neutral, says Colosi. Both are fertilizer intensive, which goes a long way toward increasing the greenhouse gas requirements of the biofuels they produce. Their production also includes drying processes that use large amounts of energy derived from fossil fuels, further compounding the emissions the biofuels ultimately produce and pushing them farther away from carbon neutrality.
Still, biofuels have the potential to become carbon-neutral in the future. Plants from canola grown in the fields of North Dakota, algae raised on municipal sewage in Louisiana and sugarcane raised in Brazil all sequester carbon dioxide. If the carbon dioxide they release as feedstock in biofuels equals the amount they sequestered as crops, then they can be considered carbon-neutral. This equation is still years away as far as biofuels go, however. The process of converting plants to fuel requires too many additional steps right now.
Because plants are comparatively equal in their potential carbon neutrality -- ideally any feedstock will only release as much carbon as it has sequestered -- researchers are spending most of their energy finding ways to shave carbon dioxide emissions from production.
"This is not so much a matter of the specific biofuel, but rather of the entire process to produce the biofuel," explains Hans Blaschek, director of the Center for Advanced BioEnergy Research at the University of Illinois.
Cutting Down Emissions
Blaschek focuses on biobutanol, a high-energy alcohol derived by fermenting plants. Biobutanol cuts down on carbon dioxide emissions because it can be transported through the same infrastructure currently used to transport oil and gas. This represents an advantage over ethanol.
Biofuel researchers are also looking to bridge the gap between present and future through the fairly primitive method of simply burning plants. This produces bioelectricity and, when used to power refineries that make biofuel, can contribute to a reduction in carbon dioxide emissions.
"Based on what I see right now, I'm very enthusiastic about switchgrass bioelectricity," Colosi says.
This perennial grass is native to North America and can thrive in marginal land, which means it poses less competition to food sources than other feedstocks, like corn or soy. Food versus fuel is just one more pitfall in biofuel production.
Switchgrass is also easily harvested and dries quickly in
the sun, which means it doesn't require fossil fuels to dry it. All of this
makes the plant an attractive fuel source, when burned with coal.
"This should give us the nearest thing we have to 'greenhouse gas neutral' bioenergy in the immediate future," Colosi says.
As researchers manage to strip away the energy inputs and carbon dioxide inputs required to produce biofuels, the energy sources will edge closer toward carbon neutrality. They're not there yet, but when there is enough biofuel to fully power biofuel production, a closed loop may be achieved, and could lead to real carbon neutrality.
Image: iStockphoto
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