Grass holds promise for saving fuel, environment

(NC&T/UM) But the grass, called switchgrass, is more than just a biofuel that could help farmers rely less on increasingly expensive fossil fuels. Switchgrass also has potential environmental benefits for the Chesapeake Bay and beyond&from the time it's planted until it's burned for heat.

Ken Staver, a research associate in the College of Agriculture and Natural Resources, has been investigating how switchgrass fits into Eastern Shore agricultural systems, from its production and role in riparian nutrient cycles to its eventual use as a home-grown fuel to supply farm heating needs.

"For a long time switchgrass has been considered to have potential for use in buffer areas to scavenge nutrients lost from cropland before they reach the Bay," Staver says "But there also is growing interest in its potential to help on the atmospheric carbon dioxide problem. Higher fossil fuel costs also make switchgrass more economically viable as an on-farm fuel than when I started working with it back in the early 1990s."

Switchgrass is a tall grass native to the Chesapeake that a number of farmers already plant to create wildlife habitat and reduce pollution from runoff. "Grasses grown in buffer areas near streams and rivers have long been considered to be effective for keeping cropland nutrients from running off into waterways," says Staver.

Ken Staver in field of switchgrass. (Photo: U. Maryland)
"Unlike most other grasses, switchgrass stands up well in the field during fall and winter, which improves its combustion characteristics, primarily as a result of leaching of most of the potassium out of the standing switchgrass. High potassium levels in grasses have always caused problems in grass-fired boilers, but by waiting until early spring to harvest, we can get around this problem with switchgrass."

While burning straw for heat has a long history in Europe, using grass as a biofuel has not been heavily studied in the United States. Researchers in the South, where switchgrass has been pushed for high yields, are studying large-scale use of switchgrass to create ethanol as a significant replacement for fossil fuel.

"The ethanol route probably is the most important from a national perspective since the big problem is a replacement for liquid transportation fuels," says Staver. "The problem with ethanol production and electricity generation is that there isn't much technology currently available for use at the farm scale. Even if there were, the cost would most likely be prohibitive."

So Staver is focusing on different an application, one more appropriate for Maryland farmers. Switchgrass is cut and baled with typical hay-making equipment, and the bales are loaded directly into a boiler designed to burn cereal straw. This system can replace fossil fuel heating in plenty of places on farms: buildings, greenhouses, in dairies for heating hot water, grain drying and aquaculture systems.

And as Staver explains, "It's the only way to use switchgrass as a biofuel that is available now and on a scale that is appropriate for use on typical Maryland farms, given our land base and switchgrass production potential." Other than the boiler, the rest of the heating system is the same as conventional boiler systems, and according to Staver, has worked quite well so far. "The big drawback is that it's a batch-fired system, which means more work than an oil- or propane-fired system where a thermostat controls fuel supply to the boiler," he says. "But from a cost standpoint we may be getting to a point where farmers consider the extra work worthwhile, especially if they also get some incentives for protecting water quality and reducing carbon dioxide emissions."

Another environmental benefit of switchgrass is that when used as a fuel, the net long-term output of carbon dioxide is less than with fossil fuels. But burning grass also can produces smoke. "Grass burning done poorly can be very bad in terms of air quality," says Staver. "Grass is tricky because the surface area of the fuel is so great. We've had some problems getting the smoke output to acceptable levels. Lately I've been looking into trying to get it pelletized to help increase combustion efficiency." Staver hopes the rise in oil prices will turn more attention to renewable energy sources like switchgrass. "The total harvested energy content per acre of switchgrass is equivalent to that of 530 gallons of heating oil," Staver says. "With a two to three dollars per gallon cost for heating oil, the per-acre value of switchgrass is starting to look more attractive.

"Switchgrass has the potential to be an economic energy source for Maryland farmers and also help them meet increasing local demands for reduced nutrient losses, as well as contribute to solutions of national and global problems related to use of fossil fuels."

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