## Study Finds Switchgrass Most Efficient of Four Perennial Grasses for Cultivation as Biofuel Feedstock Crop

##### 24 November 2009

A study by researchers at Oklahoma State University concluded that of four perennial grasses that could be grown as dedicated biofuel feedstock crops—bermudagrass, flaccidgrass, switchgrass, and weeping lovegrass—switchgrass is the most efficient in terms of dry biomass per dollar cost.

An earlier US Department of Energy (DOE) and Department of Agriculture (USDA) study concluded that 20 million US hectares (49.4 million US acres) of cropland, idle cropland, and cropland pasture could be converted from current uses to the production of perennial grasses, such as switchgrass, from which biomass could be harvested for use as a biofuel feedstock. Economically viable production of a perennial grass monoculture from which substantial quantities of biomass are removed annually is expected to require nitrogen fertilizer. The Oklahoma researchers designed and conducted experiments to determine the most efficient grass species for such an application, the level of nitrogen required, and optimal harvest frequency from among the four grass species.

Regents Professor Emeritus Charles Taliaferro, designed and conducted an experiment to determine biomass yield from alternative levels of nitrogen fertilizer for a single and double harvest per year system for the four perennial grass species. Agricultural economics graduate student, Mohua Haque, used the data produced in the field experiments to determine the most economical species, level of nitrogen, and harvest frequency for several sets of nitrogen fertilizer prices and hypothetical biomass prices.

For the soil and weather conditions that prevailed at the experiment site for the duration of the study, switchgrass clearly produced more dry biomass per dollar cost than the other three species. If perennial grass for biofuel feedstock is the best alternative for a field, and if the biomass price exceeds the cost of production, the optimal strategy would be to establish switchgrass, and in post-establishment years, to fertilize with 60 pounds of nitrogen per acre per year, and to harvest once per year after senescence.

—Mohua Haque

If an economically viable system for conversion of biomass from perennial grasses to biofuels is developed, millions of acres may be bid from current uses and seeded to switchgrass.

Results from the study will be incorporated into a model at Oklahoma State University to evaluate the economic potential of alternative cellulosic biofuels production systems for Oklahoma. The goal of the research effort is to construct and solve models to determine the optimal number, size, and locations of cellulosic biorefineries, feedstock production counties, harvest months, fertilizer levels, number of harvest machines, storage strategy, and feedstock transportation flows.

The study was funded by the USDA Cooperative State Research, Education, and Extension Service and by Oklahoma State University. Results from the study were published in the November-December issue of the Agronomy Journal.

Resources

• M. Haque, F. M. Epplin, and C. M. Taliaferro (2009) Nitrogen and Harvest Frequency Effect on Yield and Cost for Four Perennial Grasses. Agron J 101:1463-1469 doi: 10.2134/agronj2009.0193

With 100 million acres of corn cobs and 1/2 the stalks we could get around 30 billion gallons of biofuel each year. Combine that with 30 billion gallons per year from this and we have more than 1/3 of the fuel needed for cars each year.

This is why we need FFVs. If all cars sold in the U.S. after 2012 are FFV, we would have 1/3 of all cars on the road be FFV by 2017, we would reduce oil imports by 15%. That means no increase in oil imports from 2010 levels and perhaps a slight decrease depending on fuel economy of the new cars.

Is switching from fossil to agro-fuels the the best way to reduce oil import?

Finding ways to reduce overall liquid fuel consumption by up to 5% per year may do as much if not more while reducing GHG.

CAFE could be updated to mandate this 5% annual improvement. The Big-3 are in no position to complain with all the \$B they got from the public. Progressive partial and/or total vehicle electrification may be one of the ways to meet updated CAFE figures. Why not?

"Best" is one of those subjective terms. If we substitute 50 billion gallons of oil based fuels with biofuels, we use 50 billion gallons less oil derived fuels. This is a fact and whether it is best, I will leave to someone else to judge.

SJC:

Did you consider that it may take 35 billion gallons of liquid fossil fuel to produce 50 billion gallons of agro-fuel?

The net gain may be as low as 15 billion fossil fuel gallons.

Reducing (any type) liquid fuel consumption has a direct and immediate effect.

I would like to see the sources for your statement. Biomass gasification is proven for decades and cost effective.

Do both.

SJC:

Figures were based on actual (2008) corn based ethanol production. Nobody really know what future converters will provide. We are stuck with corn based ethanol for a long while and it is not very energy efficient.

Could USA switch to sugar cane ethanol (in limited areas) to change the energy in/out ratio?

Will future improved cellulosic ethanol have more favourable energy ratios? Maybe by 2020+.

Meanwhile, technologies already exist to improve/reduce fuel consumption by 5% per year for most vehicles, including heavy trucks, locomotives, tanks, buses, taxis and aircraft etc.

If done progressively (5%/yr) the country would not only cope with it but benefit through development and implementation of new technologies. Sitting still is not the right way for the future. The agro-fuel pathway is misleading because it will not only put undue pressure on food availability and cost, but it would postpone the inevitable switch to cleaner more efficient vehicles. Fixing a problem with something almost as bad is not always recommendable.

I think everyone has argued that corn ethanol is a wrong way to go. Gasification is proven, you take in biomass like corn stover and produce whatever you want. I favor renewable methane because it can be piped to regions and converted to synthetic fuels closer to the point of use.

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