Grassoline: Can we fuel cars with grass?

An E85 Ethanol Hyundai is displayed at a car show. See more pictures of alternative fuel vehicles.
Mark Renders/Getty Images


­In 2006, the United States consumed an average of almost 20.6 million barrels of petroleum per day, the equivalent of more than 865 million gallons of o­il [source: Energy Information Administration]. Oil powers your car on a trip to the grocery store. It helps industry develop and fosters technological advances in science and medicine. It also creates a tremendous amount of wealth: The global economy is based in large part on oil drilling, refining, transportation and distribution.­


But oil is a finite resource produced from the fossilized remains of ancient marine plants and animals. It takes at least 10 million years for fossilized remains to become crude oil, and people use oil much faster than it is created. Eventually oil production will peak, and we will begin to run out. Some estimate that this peak has already occurred; others see it taking place in the near future. Either way, most people believe that we are in the midst of an impending energy crisis. After all, petroleum plays such a big role in daily human activity. What happens when we run out of oil?


­The energy sector spends billions on the quest for alternatives to gasoline. But the next energy source has to do more than just supply the world with power. With increasing concerns over greenhouse gases (GHGs) from fossil fuels leading to glob­al warming, the next fuel has to be clean, too. It has to be affordable, and it has to help sustain the economy.

The next generation of fuels needs to arrive quickly, to help people transition from petroleum. After all, the world can't grind to a halt for a decade or two while the next fuel is developed and implemented.

All of this put together sounds like an impossible laundry list of demands on any fuel source. That's why it's so surprising that, after a just a few years of research, an energy source that seems to fulfill all of these obligations is emerging.

Ethanol (ethyl alcohol) is a form of fuel derived from the complex carbohydrate­s in plants. For decades, researchers have been aware of its potential as a fuel. But the process to produce ethanol inexpensively and efficiently has been elusive -- until now, some scientists say.

A fast-growing grass known as switchgrass can be found around the United States, Canada, Central and South America, and parts of Africa. And, if it continues to show the kind of promise it does now, it may be what you use to fuel your car in the next 20 years. So how can grass become fuel? Read the next page to find out about the sunny forecast for switchgrass as an answer to the impending energy crisis.



Researcher David Bransby inspects Alamo variety switchgrass on a University of Alabama test plot.
Courtesy Warren Gretz/National Renewable Energy Laboratory

Research into sources for biological fuels -- biofuels -- has included everything from chicken fat to wood chips. But processing most of them yields a low net energy ratio -- the amount of energy each unit puts out isn't much more than the energy put into its production. Cost has also been a problem: Techniques for extracting fuels from plant and animal resources are currently expensive, which would be reflected at the fuel pump. But the more researchers crunch the numbers on switchgrass, the more it looks like a good candidate for an alternative fuel source.

Switchgrass is a n­ative perennial species to the Americas. It grows quickly and easily on plains. It's a tough, hardy species -- in some cases, it's considered invasive. A three-year study in North Dakota published in 2005 showed that, when left alone, some varieties of the grass can produce an average yield of more than seven tons of biomass -- the harvested plant material -- per acre, depending on precipitation and soil type [source: U.S. Department of Agriculture].


­The grass is also resistant to drought and requires little, if any, fertilizer. This means that it requires less fossil fuel expended on production. Tractors used to spread fertilizer and fuel the pumps that irrigate fields require fossil fuel. Less irrigation and less fertilizer, then, means reduced energy input, which in turn means less cost and fewer greenhouse gas emissions. What's more, switchgrass proponents say that fuel produced from the plant would make the United States more secure and independent, since it could be grown in America rather than imported from other nations.

The fuel produced from switchgrass feedstock -- the raw material used to produce a distilled fuel -- is cellulosic ethanol. This alcoholic fuel is created by a chemical process of breaking down the cellulose -- the structure that makes up the cell walls in the plant. Once the cellulose is broken down into its basic components, yeast is added, and it's fermented into alcohol. After it's refined, the ethanol produced can be used as fuel.

The more cellulose available for extraction from a plant the more valuable it becomes as a source of ethanol. And switchgrass has lots of cellulose. Around 70 percent of the plant is composed of these complex carbohydrates [source: BioCycle]. Even better, lignin -- a byproduct created when water is eliminated from cellulose -- has shown promise for use as a fuel to power ethanol production plants. If lignin can be harnessed, this could make ethanol processing self-sustaining.

Beginning with the production of fertilizer used to grow the grass and ending with transportation for distributing ethanol, Argonne National Laboratory researcher Michael Wang calculated the energy ratio for switchgrass. He found that every one unit of energy put into cellulosic ethanol production from switchgrass created 10 times the energy output. This is much higher than ethanol derived from corn. By contrast, gasoline has an energy ratio of 1 to 0.81, which means it requires more energy to produce than it yields. Wang also found that switchgrass ethanol may require 70 percent less fossil fuel to produce than gasoline and E85 ethanol -- a mixture of 85 percent ethanol and 15 percent gasoline -- emits 86 percent fewer GHGs than gasoline does. [source: Wang].

It sounds like switchgrass as an alternative fuel has everything going for it. So what's the hold-up? The refining process seems simple, and in fact it is, relatively speaking. But making ethanol from switchgrass faces some challenges. Read the next page about the difficulty in distilling ethanol from switchgrass.


Problems and Solutions of Switchgrass

E85 ethanol is appearing at more gas stations, like this one in Washington. D.C. The fuel may be sold for as little as $1 per gallon if researchers can streamline the production process.
Chip Somodevilla/Getty Images

While it's becoming clearer with the publication of each new study of switchgrass that the plant may play an important role in future energy relief, the word "future" is key. Presently, the process of extracting cellulose from the plant is proving difficult and expensive.

Cellulose derived from plant material is produced by any of a variety of enzymes, depending on the kind of plant material being used. These catalysts dine on complex carbohydrates, like sugars, and expel cellulose and carbon dioxide as waste in the process. These enzymes are expensive, however, around 20 cents for every gallon of purified ethanol [source: Federal Trade Commission]. What's more, the fermentation process of cellulose with yeast requires a different enzyme, further raising costs. In 2006, plant geneticist Albert Kausch said that with current cultivation and production methods, the cost per gallon of cellulosic ethanol would be $2.70. That's still cheaper than gas­oline, but Kausch believes it could be brought down to around $1 per gallon [source: Newswise]. One of the ways to achieve this dramatic cost reduction is to develop cheaper enzymes and find a single enzyme that can both break down cellulose and ferment ethanol.


One of the other problems facing ethanol is getting it from refineries to fuel stations. Ethanol is highly corrosive and can't be shipped via pipelines as oil and petroleum can. This means that it must be transported by trucks, which both adds to the costs of production and lowers the energy ratio, since big tanker trucks require more fossil fuels to transport the ethanol for distribution.

Argonne National Laboratory's Michael Wang tells HowStuffWorks that the challenge of distributing ethanol could, in part, be overcome by using rail systems to carry it as far as possible. "When you refine it in the Midwest and transport it to the West, transportation is a problem," he says. "You would have to use rail. But when transporting it short distances, it doesn't make much difference [to the net energy ratio]."

The other problem switchgrass ethanol currently faces is the amount of land available for its cultivation. A University of Tennessee analysis concluded that the United States could produce a total of 153 million dry tons of switchgrass and crop residue -- the stuff that's left over after agricultural harvesting and production, like stems and seeds -- annually as ethanol feedstock. Its figures show that this would result in a 5.3 percent reduction in annual gasoline consumption in the United States -- far less than expected, and much less than the 35 billion gallons of renewable fuel President George W. Bush called for by 2017 in his 2006 State of the Union address.

Like enzyme research, technology could also overcome this hurdle. Jason Grumet of the National Commission on Energy Policy (NCEP) suggests developing strains of switchgrass that could increase ton-per-acre yields, increasing the efficiency in ethanol production by one-third and doubling the fuel efficiency of all vehicles in America [source: U.S. Senate].

The money is definitely there to overcome these hurdles. Both energy companies and crop research conglomerates are pouring money into cellulosic ethanol facilities. BP Amoco PLC gave the University of California - Berkley and the University of Illinois - Champaign a combined $500 million to fund a research facility. Chevron Corporation gave the University of California - Davis $25 million and the Georgia Institute of Technology $12 million. And the Oak Ridge National Laboratory received $125 million from the U.S. Department of Energy for cellulosic ethanol research [source: DeMonte]. Still, many companies are looking to the United States government to help foster research and development by providing investment guarantees and tax breaks for financiers who bet on cellulosic technology.

­ With the amount of money pouring into cellulosic ethanol research and the possibility that more is on the way -- not to mention the enthusiasm and public support -- it's hard not to imagine that within just a few decades, switchgrass-based ethanol will be filling our cars. But switchgrass also has its skeptics. Some don't think the grass lives up to expectations, and others fear the consequences if it does. Read about biofuel skeptics on the next page.


Biofuel Criticism

Skeptics of biofuel are concerned that funding for food aid programs, like Feed the Children (above), will dry up if excess food is used as fuel.
Layne Murdoch/NBAE via Getty Images

Competition is tight between corn and switchgrass over which will serve as the feedstock for future ethanol production. Because some areas that grow corn can't grow switchgrass, and vice versa, many regions have a vested interest in the outcome of the alternative fuel debate. Based on research into production costs, energy ratios and GHG emissions, it appears corn-based ethanol simply can't compete with ethanol made from switchgrass.

But while ethanol made from the two crops is similar in many respects, the process by which switchgrass is turned into fuel makes it the superior choice for many researchers, politicians and activists. Corn ethanol production, for example, uses only the grain (the stuff you eat) to produce ethanol. The rest is cast off -- although, ironically, the crop residue can be used in cellulosic ethanol production.


Another advantage switchgrass has over corn is the amount and type of land it requires. In Iowa -- a state with better-than-average soil -- the average crop yield was roughly 4.8 tons per acre in 2005. The 2005 North Dakota study, mentioned before, showed a yield of around seven tons of switchgrass per acre. And switchgrass doesn't require the best soil to grow well. It can be grown on land not currently used for crops.

A report produced by Oak Ridge National Laboratory concluded that fueling half of the vehicles on the road in the United States today with ethanol would require 180 million acres of land to grow switchgrass. This accounts for 40 percent of the land already in use for agriculture in America [source: U.S. Senate].

But the NCEP's Jason Grumet believes that with "steady but unremarkable progress" in research and development, we could get the amount of land needed to produce that much ethanol down to 30 million acres in 20 to 30 years. Grumet mentions that that's about the amount of acreage in the Conservation Reserve Program (CRP), a federal program that pays farmers to set aside land as fallow to reduce the environmental impact of agriculture [source: U.S. Senate].

Grumet isn't the only person to imply that switchgrass could be grown in marginal land. After all, it's been shown to improve the soil where it's planted, and CRP land could benefit at the same time feedstock is being grown for ethanol production. But not everyone believes that industrial switchgrass production is the best use for CRP land. Skeptics argue that most land enrolled in the Conservation Reserve Program is set aside because the soil won't produce high-quality crops. If switchgrass becomes the next fuel source, and major companies pump large amounts of money into its production, these critics arg­ue that these same companies will want the highest yield possible. This would be best realized by using the best land available. Which means that some arable land would go from food production to energy production.

We use a small portion of food crops for fuel today. If we come to rely on biofuels as our energy source, energy and food may come into direct competition for resources, specifically land.

This concerns some, including Dr. Eric Holt-Gimenez, of the Institute for Food and Development Policy. When fuel prices rise, so too do food prices, due to the increased cost in production and transportation. Holt-Gimenez argues that if food and energy compete for land, food prices may have a reciprocal effect on energy prices. What's more, he says that food surplus programs for hungry countries may dry up since surplus food could be used as biomass for ethanol [source:Holt-Gimenez].


There are other concerns about cellulosic ethanol, as well. Some believe the claims of its potential are too rosy, based on studies which demonstrate that cellulosic ethanol doesn't have the energy ratio other studies purport. But these studies are fewer in number -- and receive far less attention -- than those which demonstrate switchgrass' potential. And if funding and public opinion are indicators for progress, it looks like switchgrass ethanol is a go.

For lots more information on biofuels, energy and related topics, read the next page.


Lots More Information

Related HowStuffWorks Articles

More Great Links

  • Berdhal, John, et al. "Biomass yield of diverse switchgrass cultivars and experimental strains in western North Dakota." Agronomy Journal. April 15, 2005. ?seq_no_115=164799
  • Bullis, Kevin. "Will cellulosic ethanol take off?" Technology Review. February 26, 2007.
  • Burden, Dan. "Switchgrass profile." Agricultural Marketing Resource Center. June 2005. NRMODE=Published&NRNODEGUID=%7bF099CBB7-A693-4DFD-A0B6- E6D3CB969B96%7d&NRORIGINALURL=%2fagmrc%2fcommodity%2f biomass%2fswitchgrass%2fswitchgrassprofile%2ehtm&NRCACHEHINT= NoModifyGuest#
  • Clark, Giles. "Plant protein may aid biofuel production." Biofuel Review. April 30, 2007. &task=view&id=943
  • English, Burton C., et al. "Estimated Economic Impacts on the Agricultural Sector and the Nation's Economy of Supplying Feedstock to an Energy Sector." University of Tennessee. August 22, 2007.
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  • Lang, Susan S. "Cornell ecologist's study finds that producing ethanol and biodiesel from corn and other crops is not worth the energy." Cornell University. July 5, 2005.
  • Ratliff, Evan. "The plant that will save America: The chemistry." Wired, pp 160-161. October 2007.
  • Wang, Michael Q. PhD. "Energy and Greenhouse Gas Emissions Impacts of Fuel Ethanol." Argonne National Laboratory. August 23, 2005. Meeting_050823.ppt
  • Woolsey, James R. Hearings on grains, cane and automobiles: Tax incentives for alternative fuels and vehicles." U.S. Senate Committee on Finance. April 19, 2007.
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