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Switchgrass to Be Twice as Efficient Ethanol Crop as Corn

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Devoting valuable grain crops to fuel production has had an immediate negative impact on the global food supply

Devoting valuable grain crops to fuel production has had an immediate negative impact on the global food supply, reducing supply and pushing prices higher, even as one billion people suffer from chronic hunger. In the United States, high prices and economic crisis mean on in eight are now insufficiently able to access adequate food supplies. But a new generation of crop-based biofuels will be more efficient and need not interfere with the food supply.

Switchgrass can yield 1,000 gallons of fuel per acre planted, while miscanthus (elephant grass) is projected to yield 1,250 gallons per acre. By comparison, corn yield only 400 gallons of ethanol per acre, and even sugarcane only 650. Oil palms produce 610 gallons of biodiesel per acre planted, while coconut yields only 276 gallons per acre. (Figures for ethanol come from the North Carolina Cooperative Extension Service, for biodiesel from the National Sustainable Agriculture Information Service.)

The United States is shifting its biofuel focus to grasses, many of which are native to the prairies where they will be planted —an ecological selling point—, and those new crops are expected to yield a higher return not only per acre planted, but per dollar invested, helping to accelerate to the shift from petroleum-based fuels to biofuels, while reducing costs and expanding a new, native energy sector. And certain biofuel grass crops would be expected to produce 13 times as much energy as petroleum, once optimally refined.

According to Scientific American:

Farmers in Nebraska and the Dakotas brought the U.S. closer to becoming a biofuel economy, planting huge tracts of land for the first time with switchgrass—a native North American perennial grass (Panicum virgatum) that often grows on the borders of cropland naturally—and proving that it can deliver more than five times more energy than it takes to grow it.

Working with the U.S. Department of Agriculture (USDA), the farmers tracked the seed used to establish the plant, fertilizer used to boost its growth, fuel used to farm it, overall rainfall and the amount of grass ultimately harvested for five years on fields ranging from seven to 23 acres in size (three to nine hectares).

Ken Vogel, a plant scientist for the USDA, says switchgrass will produce 540% of the energy required to produce and refine it, while corn-based ethanol produces only 125% of the energy required to produce it. That’s a net energy gain of 440% as compared to 25%, over and above the energy invested. By that measure, in the optimum case, switchgrass can be 5 times as productive in terms of planting and 17 times as efficient in energy production.

The switchgrass fuel-production process is itself not only more efficient than other biofuel sources, but can free up food-oriented crops to continue toward building grain supplies and shoring up the global food supply, helping to keep prices within reason and reduce the economic impact of the fuel-economy transition.

In 2008, Science Daily reported that:

In a biorefinery, switchgrass biomass can be broken down into sugars including glucose and xylose that can be fermented into ethanol similar to corn. Grain from corn and other annual cereal grains, such as sorghum, are now primary sources for ethanol production in the U.S.

In the future, perennial crops, such as switchgrass, as well as crop residues and forestry biomass could be developed as major cellulosic ethanol sources that could potentially displace 30 percent of current U.S. petroleum consumption, Vogel said. Technology to convert biomass into cellulosic ethanol is being developed and is now at the development stage where small commercial scale biorefineries are beginning to be built with scale-up support from the U.S. Department of Energy.

With the DoE and the USDA both helping to fund an aggressive shift to high-efficiency crop-based fuels, designed not to erode the food supply, switchgrass ethanol and biomass-based cellulosic ethanol have the potential to displace petroleum as the fuel-base of choice. Ethanol may not replace petroleum-based fuels across the entire energy economy, but they would be able to meet the combustible fuel demand running parallel to a comprehensive shift toward zero-combustion renewables like wind and solar for electric and battery power.

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