Switchgrass
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{{Taxobox | color = lightgreen | name = Switchgrass | image = Panicum virgatum.jpg | image_width = 240px | regnum = Plantae | divisio = Magnoliophyta | classis = Liliopsida | ordo = Poales | familia = Poaceae | genus = Panicum | species = P. virgatum | binomial = Panicum virgatum | binomial_authority = L. }}
Switchgrass (Panicum virgatum), also called Tall Panic Grass, is a warm-season plant (C4 carbon fixation) and is one of the dominant species of the central North America tallgrass prairie. Switchgrass can be found in remnant prairies, along roadsides, pastures or as an ornamental in gardens. Other common names for this grass include Wobsqua grass, lowland switchgrass, blackbent, tall prairiegrass, wild redtop, and thatchgrass.
This hardy, perennial grass begins growth in late spring. It can grow up to 1.8-2.2 m in height, but is typically shorter than Big Bluestem Grass (Andropogon gerardii) or Indiangrass (Sorghastrum nutans). The leaves are 30-90 cm long with a prominent midrib.
Its flowers have a well-developed panicle often up to 60 cm in length and bears a good crop of fruits, which are 3 to 6 mm long and up to 1.5 mm wide. The fruits are developed from a single-flowered spikelet. Both glumes are present and well developed. When ripe, the seeds sometimes take on a pink or dull-purple tinge, and turn golden brown with the foliage of the plant in the fall.
Switchgrass is a short rhizomatous plant that tends to resemble a bunch grass. As an ornamental grass, it is easily grown in average to wet soils and in full sun to part shade. It is very drought resistant. Establishment is recommended in the spring, at the same time as maize is planted.
Switchgrass is grazed by all kinds of animals. Grazing sheep and horses on monoculture switchgrass stands should be avoided. Due to its hardiness and rapid growth, switchgrass is often considered a good candidate for farming as feedstock or for biofuel production (for example, ethanol). It was in this capacity that President George W. Bush mentioned it in his 2006 State of the Union address. Many farmers already grow switchgrass, either as forage for livestock, in wildlife areas, or as a ground cover, to control erosion. Switchgrass, like many other higher yielding and more water efficient annual and perennial grasses, is a source of cellulose and hemicellulose. These may be converted to fermentable sugars, given the right enzymes and environments. Currently, the most efficient method for converting switchgrass into fermentable materials is the rumen. Cattle, sheep and horses are far more efficient at grass-based cellulose conversion than is our National Renewable Energy Laboratory, or their partner, Novozyme. President Bush has once again bought into a boondoggle when he proposes to convert valuable cropland into industrial-scale grass production for ethanol. Switchgrass has the potential to produce the biomass required for production of up to 100 gallons of ethanol per metric ton. A high yield like this makes it a very attractive crop to grow as the value by far exceeds any other crop. Yet, some studies claim that switchgrass is not a viable alternative, requiring 45 percent more fossil energy than the fuel produced. David Bransby, professor of energy crops at Auburn University, disagrees. He argues that for every unit of energy input, switchgrass yields four units out. Clearly, the viability of switchgrass as an alternative fuel remains contentious.
Switchgrass can be made into ethanol using a distiller.
bioenergy.ornl.govswitchgrass profile
References
- Image Archive of Central Texas Plants
- Switchgrass - Has excellent closeup photos of spikelets.
- Claims on viability of switchgrass, biofuels
- Economics of switchgrass production
- Interview with David Bransby, professor of energy crops at Auburn University
- Acres of farmland in the United States
- bioenergy.ornl.gov Estimated yields from switchgrass
- www.usask.ca
- www.carbohydrateeconomy.org Ethanol energy balance calculations