New Biofuel Crops Could Offer a Climate Advantage for the Midwest

By Alyson Kenward

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A few miles south of the University of Illinois’s Urbana-Champaign campus, a series of small fields used by agricultural researchers to study corn are slowly being taken over by fast-growing grasses. They aren’t weeds, however; the grasses grow in tidy plots at least one acre large, with stalks that top out as high as 12 feet, well above the tallest rows of corn. The grasses, called switchgrass and miscanthus, are relative newcomers to Illinois, but as promising raw materials for making biofuels, they may populate farmers’ fields in the years to come as America’s demand for renewable fuels rises.

Plots of miscanthus and switchgrass outside Urbana, Illinois. Here, researchers from the University of Illinois are studying new biofuel crops. Credit: David Dragg/flickr

Today, these Illinois fields are testing grounds for some of the country’s future bioenergy crops. Among the plots of grass, scientists meticulously monitor how the plants grow and respond to their surroundings. With particular focus on switchgrass and miscanthus grasses, researchers are assessing the potential for these crops to replace corn as the number one source for biofuels. They are also trying to identify what farmers will need to know if and when they’re ready to swap out corn crops for these perennial grasses.

“We’re trying to figure out how these plants respond to the climate,” says biologist Carl Bernacchi from the U.S. Department of Agriculture and the University of Illinois. By learning how these different crops react to real growing conditions, Bernacchi says they can estimate what might be the impacts if vast parcels of the Midwestern landscape are devoted to growing these new bioenergy crops.

Today corn is the most popular source of ethanol biofuel in the U.S., largely because it is a crop that Midwestern farmers have grown for decades. But as the country begins to demand more renewable fuels in place of traditional fossil fuels, researchers have been shopping around for more efficient renewable raw materials. They’re looking for crops that will yield more fuel than would corn on the same space of land, and do so with fewer inputs of fertilizer and cultivation effort, both of which burn through a lot of fossil fuel.

Growing Grasses for Fuel

Two of the leading candidates to replace corn are switchgrass and miscanthus grasses. As researchers have shown in the test fields of Illinois, these perennial crops can be densely planted and without much effort or fertilizer, they grow rapidly. Even better, an acre of land planted with these grasses promises to yield more material that can be converted to ethanol or other biofuels than the same acre planted with corn.

Switchgrass is native to the American prairies, and already some farmers grow and sell it to power plants that burn the raw material for energy. Miscanthus, on the other hand, has Asian origins, and though some European countries, like Germany and Italy, grow a lot of miscanthus to burn with coal for electricity, there is just a handful of American farmers currently growing it. In the past decade, however, researchers at the University of Illinois and elsewhere have focused on the biofuel potential of these different grass species and are now closely studying both varietals.

Strands of miscanthus may eventually be used to generate renewable fuels in the U.S.. Credit: Stephen Long/flickr.

To the farmers’ credit, there isn’t yet much reason to grow miscanthus on home soil. American markets for both raw miscanthus and switchgrass are nearly non-existent because energy and biotech companies haven’t developed the technology that can convert the material into a biofuel on an affordable scale. Until this technology is commercialized, farmers won’t hurry to swap out their cornfields for grass. But on the expectation that these grasses will eventually find a market, researchers are now trying to anticipate what might happen if farmers across Illinois and the rest of the Midwest make the crop switch.

How to Count All the Carbon

In 2005, the U.S. established a mandate to increase the amount of renewable fuels the country consumes each year. This Renewable Fuels Standard (RFS) was set up partly to improve the nation’s energy security by reducing dependence on foreign oil sources, and also to lower greenhouse gas emissions. Now, each year the Environmental Protection Agency (EPA) is responsible for setting how many gallons of renewable fuel must be produced under the RFS. They also decide which fuels have greenhouse gas emissions low enough to qualify them for the financial benefits offered under the RFS. And determining greenhouse gas emissions for biofuels requires accounting for all the sources of such emissions.

“People tend to think that using biofuels automatically reduces greenhouse gas emissions,” says Princeton University environmental policy specialist Tim Searchinger. He says that it’s easy to think that burning fuels doesn’t add extra emissions to the atmosphere because the plants used to generate biofuels absorb carbon dioxide (CO2) as they grow.

“The assumption is that the carbon going out tailpipe of a car doesn’t count.”

According to the Renewable Fuel Standard, each year the U.S. needs to increase the number of gallons of renewable fuels it produces. Credit: Climate Central.

Yet, this misses CO2 emissions from fossil fuels that are burned while producing the biofuel, such as gasoline burned in tractors and fertilizers used on the farmers’ fields, says Searchinger. When calculations factor in this additional CO2, the biofuels’ benefit is lowered.

And even this isn’t the whole story, he says, because it ignores the fact that most farmers today use their fields to grow food.

If a farmer takes his field, which he uses to produce food, and switches it to grow corn or miscanthus for biofuel production, then more land is needed to grow the missing food, or more food must be squeezed out of the remaining food-directed farmland. If additional land — in the U.S. or somewhere else in the world — is cleared of natural vegetation to grow food, there are additional carbon emissions that need to be considered, Searchinger says. For example, when new land is cleared to make way for fresh food crops, large amounts of carbon that are stored in vegetation already on that land, like trees, and in the underlying soil are released to the atmosphere.

“Not surprisingly, when you look at it that way, there isn’t always a benefit to using biofuels,” says Searchinger. “And sometimes there is even a deficit.”

In order to figure out how much carbon should be credited to a renewable fuel crop, researchers now consider how much carbon goes into or out of all the land needed to produce a biofuel. That means they count carbon saved from biofuel cropland and carbon lost when new food cropland is cleared.

For ethanol biofuel coming from cornfields in the American Midwest, when all these other emissions are considered, it turns out there isn’t much greenhouse gas advantage. And this is the reason why researchers and policy makers have turned their attention to alternative crops and new biofuels. It's a key reason why dozens of researchers across the country, including those in Illinois, are trying to learn more about crops like miscanthus.

“Our job, as researchers, is to take these different scenarios and try to understand what the environmental impacts are going to be, as best we can,” says Bernacchi. One of his Illinois colleagues, Stephen Long, has already learned that fields of miscanthus and switchgrass take in a lot more CO2 than fields of corn. Now the group is interested in other ways the grasses differ from corn, to better understand the impact of planting this alternative crop.

Climate Effects of Biofuel Crops

One possible scenario in the Midwest — even if it is five, 10, or 15 years in the future — is that farmers who mostly grow corn today could covert most of their land to different renewable fuel crops, like miscanthus or switchgrass. A transformation like this, across such an immense region, would not only change the way the landscape looks, but also could have broader impacts on climate across the middle of the country. What’s on the ground often plays an important role in local and even regional climates because the type of vegetation covering the land can influence atmospheric temperatures and humidity. 

New research from Arizona State University and Stanford University has attempted to predict just how much these different crops could influence Midwestern climate. Led by Matei Georgescu, the researchers estimated what the Earth’s surface in this region would look like with perennial miscanthus crops in place of corn. Plugging that information into a regional climate model, they found that the area could cool by as much as 1°C in the summer if grasses were planted in place of corn.

“We found that these grasses are evaporating more water, which leads to some of this cooling,” says ecologist Chris Field from the Carnegie Institute for Science in Stanford, Calif., who worked with Georgescu on this new study. Because miscanthus plants take up more water from their roots and then release more through their leaves than corn does, he says the cooling effects of having miscanthus across the entire Midwest could be dramatic.

Moreover, miscanthus grass turns green earlier in the spring than corn, and is harvested later in the fall, and Field says this longer growing season also causes the crops to reflect more sunlight away, which provides a further cooling effect.

According to Illinois’s Bernacchi, as a first guess of how these different types of crops will influence the climate, “the models in the new study are giving a good outcome.” They aren’t, however, picking up on many of the more minute details of how different crops respond to the weather and climate, so at best they are just a generalization. 

University of Illinois researcher Andy VanLoocke is studying how different perennial biofuel crops may influence climate in the Midwest. Credit: Andy VanLoocke.

So, along with graduate student Andy VanLoocke, Bernacchi is taking the approach a few steps further and looking at differences between separate perennial biofuel crops. After learning how each species responds to the regional climate they can then use that information to predict how regional temperatures and precipitation might change in the future. In the end, they expect to have a more detailed analysis of how the climate might respond to these perennials.

Overall, VanLoocke says all this research is still just an estimate of how the climate might change, but it is valuable because it can help people begin to think about how the climate will respond if the land’s surface is altered. 

And in Field’s mind, gaining a general appreciation for how vegetation influences the climate is a particularly important outcome of their research because it sheds a new light on how policy-makers might consider biofuel crops.

“Right now, we have a climate regime that is focused on greenhouse gases only, and there is good reason for this,” says Field. With burning fossil fuels adding so much CO2 into the atmosphere, he says it is helpful to think in terms of these gases.

“But one thing is a concern that we might end up with some policies that were intended to provide a greenhouse gas benefit but that give an overall climate liability,” he adds, which is one reason why he and his colleagues have made this first attempt to measure how the climate will change if perennial biofuel crops are widely introduced in the Midwest.

According to Searchinger, whose focus is on agricultural and environmental policy, it’s not surprising that researchers are trying to measure these climate changes. But he says these early results also draw attention to how much research is still needed before climate impacts are well understood.

For example, Searchinger points out that even if temperatures change on a regional scale with different crops, researchers don’t know what the global impact would be.

“I think it’s an interesting result, but I’m not sure what to do with it,” he says. Accounting for these climate effects is going to be even more complicated than counting all the sources of greenhouse gases, he explains, so it’s not clear how or when they will be incorporated into biofuel policy.

Waiting for the Miscanthus Market

If the growing number of scientific studies on miscanthus is any indication, the biofuel community’s interest in whether it could replace corn for biofuel production is taking off. But what about farmers — when will they be ready to swap their crops?

“Basically, there’s not a market for any of these [grass biofuels] yet,” says Wallace Tyner, an agricultural economist from Purdue University. “For there to be one? Essentially, farmers have to believe it will be profitable.”

According to Tyner, most farmers won’t grow miscanthus for ethanol or another biofuel until they are sure someone will pay them a price for it that makes it worth their while to grow. That requires a company to build a conversion plant that can competitively make biofuel from the new crop. But that isn’t bound to happen until the energy company knows farmers will commit to cultivating miscanthus and selling it at a price the company can afford to pay and be competitive in the fuels market, he says.

There isn't yet a market for miscanthus in the U.S., but in the future, fields of the grass may reshape the Midwestern landscape. Credit: Andrew Leakey.

“Both things have to happen at the same time,” Tyner says. “It can happen, but it’s complicated, and it will take time.”

Bernacchi, however, says farmers from around Illinois are constantly approaching him with questions about miscanthus. He says a few have even taken part of their farmland — though no more than about 10 percent each — and converted it to miscanthus. They are even turning a small profit from it, he says, but right now that isn’t by turning the harvested material to biofuel. Instead, they are making money by selling the rootstalks to other developers interested in studying miscanthus.

“Planting miscanthus now is a calculated risk,” Bernacchi explains, because it's not yet clear if and when biofuel companies will build plants to convert miscanthus. “But it’s a risk that could offer a lot of profit if this advances in the future.”