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