Real benefit of switchgrass is its ability to suck up excess nitrogen
Plant's potential as biofuel makes it even more attractive for farmers
It's easy to see why everyone is excited about the prospect of biofuels.
After all, getting oil from foreign countries hasn't worked out that well for the United States. And domestic means of extraction are problematic, too. Natural gas drilling is fraught with problems known and unknown. Coal-fired power plants are major polluters. And offshore drilling has more than lost its luster as an oil spill of epic proportions threatens Gulf Coast marine life and its habitat.
No wonder burning cornstalks and switchgrass is starting to look pretty good.
Eco-hydrologist Kenneth Staver doesn't want to be the skunk at the biofuels garden party. Indeed, he's a believer in switchgrass, having used the fast-growing native plant to fuel the boiler that heats the maintenance complex and greenhouses at the University of Maryland's Wye Research and Education Center along the Wye River.
But Maryland's Eastern Shore simply doesn't have enough agricultural land to make switchgrass a viable biofuel that could significantly reduce Maryland's dependence on oil for vehicles and homes, Staver said. If the region got into biofuels in earnest, it couldn't make a large-scale effort with locally grown crops.
Instead, he said, the real benefit of switchgrass is that it sucks up excess nitrogen, a key Bay pollutant, better than just about anything else. And, if farmers could plant the grasses in their riparian buffers and harvest some to heat their own greenhouses and farms, the crop could address two significant environmental problems.
But to make that happen, the government would have to change its policies on payments for buffers. Every year, thousands of farmers in the Chesapeake Bay watershed receive government money to take marginal land out of production and use it as a "buffer" to soak up the excess nitrogen and phosphorus that comes from soil. The program's rules do not allow farmers to harvest the plants in the buffer, although a few states have pilot programs to investigate whether that might be a good idea in the future. In those states, Staver said, farmers take a lower payment for planting the switchgrass in an acknowledgement of the crops' economic benefits.
For decades, farmers had used a grass called tall fescue in their buffers and grass waterways. The most popular variety was called Kentucky 31. A cool season grass, it was cheap, easy to establish and nearly indestructible, earning it the nickname "green concrete." But eventually it fell out of favor because it did not create diverse enough habitat for insects and birds and outcompeted native vegetation.
Later, orchard grass became de rigueur. Like tall fescue, it was familiar to the farming community and easy to establish. While both orchard grass and tall fescue trap sediment and nutrients in surface runoff, Staver suspected that neither had much potential for sucking nitrate out of groundwater.
"We knew that one of the major ways nitrogen moves through riparian zones is through groundwater," Staver said. "So we were looking for grasses that would get after that groundwater nitrate."
Staver theorized that switchgrass would be the better species for riparian buffers. It grows in wet areas, is native, and was eligible to receive the government payments. It seemed a likely candidate for a grass that could provide habitat, capture nitrogen and perhaps provide an economic benefit as a biofuel crop.
As a part of a larger project looking at options for optimizing environmental benefits from buffers, Staver grew several different types of grasses and a shrub willow at a research site alongside the Wye River. Using lysimeters to simulate groundwater conditions and monitor plant water and nitrate uptake, he spent four years conducting experiments to determine which grass could best filter nitrate out of groundwater.
Switchgrass won. Prairie cordgrass and Eastern gamagrass also showed some ability to pull nitrate from groundwater. Orchard grass, the standard bearer for so long, showed no ability to pull nitrate from underlying groundwater.
Once established, the willow shrubs actually performed the best of all the plants, although they are not commonly used as a biofuel and require more management for planting and harvest, Staver said.
Staver would like to see more farmers plant switchgrass and willow in their buffers. But few states have programs that allow the use of the plants as biofuels. Pennsylvania and New York have limited efforts. If more states did, Staver said, the farmers could use the switchgrass to supply on-farm heating needs while also meeting ever-stricter nutrient reduction goals. That, he thinks, is a more realistic future for the wonder grass, if the will is there to make a change.
"We're trying to find a way for the biofuel value to help pay for the water quality benefits," Staver said. "If oil is cheap, this won't happen on its own...how well it works from an economic standpoint depends on the price of oil."
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