Someday, your car might run on ‘grass’oline. Grasses are among the most promising new energy crops. Miscanthus, sorghum and switchgrass are all being developed as feedstocks for cellulosic ethanol.
New biodiesel crops are on the horizon, too. For example, camelina, a cool-weather oilseed, is already being grown on thousands of acres in Montana.
Here's a quick look at a few new energy crops now in development.
Versatile sorghum can be used for starch, sugar and cellulosic ethanol production.
The drought-tolerant annual grass, which is native to tropical and semi-tropical regions, is now grown in the U.S. for grain, forage and specialty sugar. Sorghum needs less water and fertilizer than corn, and fits well into row-crop rotations.
Today, about 15% of the U.S. grain sorghum crop of 7 million acres is used to make starch-based ethanol. The Corn Belt states are investigating sweet sorghum for cellulosic ethanol. High-biomass sorghum hybrids, with yield potential up to 20 dry tons/acre, are being developed as biofuel crops for Kansas, Oklahoma, Texas and the Deep South.
This perennial grass can be burned for heat and power or used to make cellulosic ethanol.
Miscanthus, native to Asia, grows 5-13 ft. tall. It's adapted to a wide range of soils in the eastern Corn Belt and the Southeast, and needs little fertilizer. Miscanthus produces no seed, so it must be vegetatively propagated. It takes two to three years to become established and has a stand life of 15 years. It's planted with modified potato planting equipment and harvested in late fall, winter or early spring with standard forage equipment.
Miscanthus grows best on productive land with adequate moisture. In Illinois test plots, it yielded 10-15 tons of biomass/acre and cost about $50/ton to produce, excluding land costs.
This hardy perennial grass can be burned for heat and power or used to make cellulosic ethanol.
Switchgrass once covered large parts of the North American continent, from the tallgrass prairies of the Great Plains to the eastern and southern grasslands. Today it's grown for forage, erosion control and wildlife habitat.
Switchgrass grows 2-6 ft. tall. The crop provides year-round ground cover, which filters runoff and reduces soil erosion. Its dense roots penetrate 10 ft. into the soil, adding organic matter and improving water infiltration and soil tilth. The massive root system sequesters three times as much carbon as no-till corn, reducing CO2 emissions by 80%.
Switchgrass flourishes in a wide range of soils, geographic regions and climates. It's well-suited to marginal and erodible land, tolerating wet sites, short-term flooding and drought. The crop is grown from seed, has a two-year establishment period and a 10-year stand life. It's also pest and disease resistant. It needs 75-150 lbs. of nitrogen(N)/acre and is harvested after a killing frost with standard forage equipment.
Current switchgrass yields range from 1 to 8 tons/acre. Yields are higher in the eastern and southern U.S. because of a longer growing season and more productive varieties. Plant scientists are working to raise yields and improve agronomic characteristics.
This low-input oilseed is a good source of cold-weather biodiesel fuel.
Camelina has been grown in Europe since ancient times for cooking oil. It thrives in a cool, arid climate and is well-suited to a small grains rotation in the Pacific Northwest and Great Plains.
The plant grows 1-3 ft. tall and produces pale green leaves and tiny seeds. Camelina is cold and drought tolerant, needs little fertilizer and can be produced with conventional equipment. It is broadcast or drilled in late fall, winter or spring, and straight combined in early July. Current crop yields range from 500 to 2,000 lbs./acre.
The crop was grown commercially this summer on 25,000 acres in Montana and will be crushed at a new crushing plant in Shelby, MT.
You already grow this biomass crop, which will supply the nation's first generation of cellulosic ethanol plants.
Corn stover — the leaves, stalks and cobs left after the grain is harvested — can be burned for heat or power or converted to liquid fuel. A 170-bu./acre corn crop produces about 2 tons/acre of harvestable biomass. That converts to about 160 gal. of cellulose-based ethanol. The same acre of corn grain produces about 480 gal. of starch-based ethanol, bringing the total fuel yield to about 640 gal./acre.
However, removing crop residues increases the risk of soil erosion and nutrient runoff. So, Corn Belt researchers are exploring ways to harvest stover while protecting soil and surface waters. Some of the things being tried include double-cropping corn and cool-season annuals, using living mulches and recycling N and other nutrients left over from corn stover refining.