The Power of Switchgrass: a Chat with Tom Juenger

As a field station near the heart of Austin, Brackenridge Field Lab hosts important research by many UT faculty. Amongst them is Dr. Tom Juenger in the Department of Integrative Biology. He studies ecological and evolutionary genetics of local adaptations in plants. He also works with a team looking at the genome of switchgrass to better understand its use as a biofuel.

Never heard of switchgrass? You’re not alone. Grasses aren’t terribly charismatic when it comes to introducing people to plant biodiversity and the practical applications for which grasses can be used. “Grasses are hard to talk about because they’re kind of non-descript,” says Juenger. “But the amazing thing is grasses are really diverse and really important. Most of our crops are grasses. There are different types of grasses that perform different types of photosynthesis. You have grasses in the tropics, in the temperate regions, in the extremes habitats throughout the world. They are often dominant members of plant communities.”

For switchgrass, it is a perennial found all over North America, but how we find it today is very different from how it used to exist not so long ago. “Historically, switchgrass was an important member of prairie communities,” Juenger says. “When you think about tallgrass prairie in the Midwest, switchgrass was one of the dominant tallgrasses. Those prairies were amazing. You could have dense vegetation for miles that would be six, seven, or eight feet tall. You would be lost in a sea of grass.”

All of this disappeared in a short amount of time with the introduction of the steel plow and expansion of mass agriculture. “A lot of people really haven’t seen prairie as it was,” says Juenger. Here in Austin, we can see remnants of these old prairies in our native switchgrass. “In a single growing season,” Juenger says, “we can get plants that are nine feet tall that you can’t reach around.”

So how does switchgrass work for biofuels? “The process starts with basically how all plants function,” Juenger explains. “Plants fix carbon from the atmosphere using sunlight, water, and photosynthesis. They make sugars stored in the cell walls and other features of the plant.” When it comes to fixing carbon, some plants are really productive at this, switch grass being an example of one.

“For us to access this energy, the most simplistic way is to just burn it,” Juenger says. “You could also pelletize the plants and turn them into basically a coal replacement. Or you can use a variety of enzymatic methods to take those sugars and turn them into liquid fuels like ethanol.”

Recognizing the urgency of finding alternative fuel sources, the Department of Energy has been investing a lot of resources into research on perennial grasses for biofuel. While there have been advancements with electrical cars and harnessing wind and solar power, Juenger explains that the batteries used with these technologies don’t work everywhere. The more demanding forms of transportation found in shipping, trucking, and airlines just can’t be powered by these batteries. This is where a carbon-neutral form of energy such as biofuels can come in.

The efficiency of switchgrass far outperforms that of other biofuel crops like corn which provides ethanol. Juenger explains: “Switch grass is native, productive, sequesters a lot of carbon, grows without irrigation or fertilization. You plant it once and harvest it over and over again.” Take that corn!  

Perennial grasses like switchgrass have the added bonus of fixing carbon below ground, and can slow erosion. They also slow the leaching of crop fertilizers into water ways that later cause problems in places we Texans are familiar with, places like the Gulf of Mexico.

Having a large space has been important for Juenger’s work on switchgrass. His research focuses on quantitative genetic experiments and that usually means there is a lot of replication inside large experiments to measure pretty subtle effects. “The greenhouses and Experimental Gardens at Brackenridge Field Lab provide the space I need and was a big reason why I chose to come to UT,” he says. He was able to start a propagation project at BFL and share the plantings across many field stations to make a network. Additionally, one of the species he works with, Panicum hallii, can be found natively at BFL. BFL’s proximity to campus has also allowed him to work more closely with undergraduates through research programs like the Freshman Research Initiative’s “Biology of Biofuels.”

Want to learn more? 

Listen to the podcast, Bio Eats World, where Lauren Richardson interviews Juenger about studying native plants — like switchgrass — can inform crop improvement strategies, the import role of switchgrass as a possible future source of biofuels, how advances in sequencing technology have unlocked the secrets hidden in plant genomes, and more.