Abstract
Photo courtesy of USDA-NRCS |
Switchgrass is a native warm-season, perennial grass indigenous
to the Central and North American tall-grass prairie into Canada.
The plant is an immense biomass producer that can reach heights
of 10 feet or more. Its high cellulosic content makes switchgrass
a candidate for ethanol production as well as a combustion fuel
source for power production. This publication discusses agricultural
production aspects of switchgrass. Varieties, seed sources, crop
establishment, management, and harvesting issues are presented.
Ecological considerations are also discussed and a case study is
presented along with references and further resources.
Table of Contents
Introduction
This publication details the production of switchgrass for use
as a cellulose-to-ethanol and direct-combustion feedstock, and focuses
on the agronomic and ecologic considerations of switchgrass production.
Ethanol production is addressed in detail in the ATTRA publication
Ethanol Opportunities
and Questions. Biofuels are carbon-based energy sources
taken ultimately from solar energy as it is captured through photosynthesis
and stored in plant tissue.
Biofuels are renewable in that plants grow back after harvest,
and can be regenerative when sustainable methods are employed to
manage, harvest, and process the crops. Ethanol, used in gasoline
(spark-plug) engines, is produced through the fermentation of plant
sugars and distillation of the mash to produce fuel alcohol. Ethanol
can be produced from crops such as corn and sugarcane, which are
high in the sugars needed for fermentation, or from cellulosic materials,
such as wood by-products and high-fiber grasses, such as switchgrass.
Switchgrass can also be directly combusted or co-fired with coal
to lower emissions associated with the burning of that fuel. However,
for switchgrass to become practical as a directly combusted fuel
in coal plants, retrofitting current boilers from coal or co-fired
applications is required. For more information on this aspect of
switchgrass, see the Chariton Valley Biomass
Project case study below.
Switchgrass can be used as a fuel source to power ethanol plants,
which results in reduced use of fossil fuels and contributes to
a more positive energy balance for cellulosic ethanol.
Although recent news has been full of exciting reports about ethanol
and switchgrass, producers need to be aware that a market for switchgrass
as an energy crop is (in 2006) scarce to nonexistent. There is intense
speculation about how, when, and whether these potential markets
will materialize. In the meantime, corn ethanol is becoming more
popular in the marketplace. In fact, 14 percent of the 2005 U.S.
corn crop was used to produce ethanol, and the percentage is expected
to grow. Cellulosic ethanol production is, from a processing and
distribution standpoint, still in a research and development phase.
As further research into cellulosic ethanol production and processing
is completed, perhaps switchgrass can become a cost-effective, viable
alternative energy source.
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Description, Range, and Adaptation
Illustration courtesy of OSU
Forage Information System |
Switchgrass (Panicum virgatum L.) is a native warm-season,
perennial grass indigenous to the Central and North American tall-grass
prairie. It is found into Canada and ecotypes have been identified
in regions from the Atlantic coast to the eastern Rocky Mountain
front. Switchgrass is historically found in association with several
other important native tall-grass prairie plants such as big bluestem,
indiangrass, little bluestem, sideoats grama, eastern gamagrass,
and various forbs (sunflowers, gayfeather, prairieclover, prairie
coneflower). These widely adapted species once occupied millions
of acres of tall-grass prairie. Now they are rarely seen, usually
on land that cannot be utilized for annual cropping. Look for native
plants like these in protected areas along fence lines, in riparian
buffers, and especially in old cemeteries and church yards across
the prairie states.
Switchgrass grows well in fine to coarse textured soils, and in
regions where annual precipitation falls between 15 and 30 inches
or more per year. It is an immense biomass producer, and can reach
heights of 10 feet or more in wetter areas of the country. In general,
ecotypical differences are related to local soil and climatic characteristics,
with eastern and southern varieties adapted to higher moisture conditions,
and western and northern varieties adapted to drier conditions.
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Switchgrass Ecotypes
and Varieties
As switchgrass evolved across North America, different ecotypes
emerged with genetic and morphological characteristics that provide
a good “fit” to a particular place. Thus ecotypes in
the south typify southern characteristics, such as long season growth
and subsequent high dry matter yield, given favorable growing conditions.
Two major types have emerged through natural selection. The upland
types favor drier soils and fare better in semi-arid climates. The
lowland varieties grow better in heavier soils and are found where
water availability is more reliable. The lowland cultivars have
the genetic ability to produce more dry matter than the upland cultivars.
Plant breeders at various Agriculture Research Stations from Texas
to Nebraska have collected seeds from local switchgrass colonies
and reproduced them into relatively uniform strains adapted to particular
locales. These strains, once some bit of uniformity is achieved
through artificial selection, are then registered as cultivars or
varieties. This simple breeding program has created the many switchgrass
varieties available today.
Research studies have determined that selecting varieties based
on location increases the survivability and productivity of a switchgrass
stand. Parrish and Fike (2005) have found
a “strong correlation between latitude of origin and yield,”
and “the main factor determining adaptation of a cultivar
was its latitude of origin, with southern cultivars having higher
yield potentials as they are moved north.”
Switchgrass varieties should therefore be chosen based upon ecotype
(whether an upland or lowland variety) and the latitude of origin.
For instance, a high-yielding southern lowland variety like Alamo
can potentially outproduce upland varieties in more northern latitudes.
Check with your local Natural Resources Conservation Service (formerly
SCS) or Cooperative Extension office for varieties adapted to your
area.
Upland Varieties |
Trailblazer |
Developed by USDA-ARS and Nebraska Agricultural
Research Division, Dept. of Agronomy, Univ. of Nebraska. Released
1984. Collections from natural grasslands in Nebraska and Kansas.
Adapted to Central Great Plains and adjacent Midwestern states. |
Blackwell |
Developed by Plant Materials Center, NRCS, Manhattan, Kansas.
Released 1944. Upland type switchgrass. Widely adapted to Kansas,
Oklahoma, southern Nebraska, and northern Texas in areas with
20 inches or more of annual precipitation. |
Cave-in-Rock |
Plant Materials Center, NRCS in cooperation with the Missouri
AES. Released 1973. Tolerant to flooding. Adapted to Midwest. |
Pathfinder |
Selected at Nebraska AES, Lincoln, ARS cooperating. Released
1967. Winter-hardy, late maturing. |
Caddo |
Selected at Oklahoma AES, Stillwater, ARS cooperating. Released
1955. Forage yield under irrigation outstanding for native grass;
recovers well after mowing. |
Lowland Varieties |
Alamo |
Developed by Texas Agricultural Experiment Station and NRCS,
Knox City, Texas. Released 1978. A premier lowland variety,
heavy yields especially in the south. |
Kanlow |
Developed at Kansas AES and ARS, Manhattan. Released 1963.
Developed for soil conservation in poorly drained or frequently
flooded sites. |
Source: Oregon State University,
2006. |
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Establishment, Management,
and Harvest
Switchgrass has been successfully established by several well-known
methods:
- conventional tillage and drill planting,
- no-till planting into crop stubble or pasture, including CRP,
and
- frost seeding.
For successful biomass plantings, plant 4 to 10 pounds of switchgrass
seed per acre at a depth of ¼ to ½ inch to obtain
a plant density of greater than two plants per square foot. If drilled
in rows, research suggests that wider spacings result in higher
yields. Row widths as wide as 32 inches have been successful in
establishing productive switchgrass stands.
Switchgrass can be no-till drilled into crop stubble or grass sod
during the winter when the grass is dormant. Drills should be equipped
with rollers or press-wheels to ensure adequate seed to soil contact.
For germination and seedling survival, the soil should remain moist
for at least one month to prevent desiccation and stand failure.
Frost seeding is the practice of broadcasting seeds during the
early spring freeze-thaw period. The action of the soil freezing
and thawing throughout the day works the seed into the soil, establishing
seed to soil contact. Seed stratification is effectively accomplished
with this method. Competition from existing perennial grasses can
be severe in frost-seeded stands. Frost seeding without burn-down
herbicides might work better in fields with some bare soil and little
competition from aggressive perennials.
Seed Sources
Oregon State University’s Forage Information System has
seed source information on the varieties listed here and more.
Some OSU variety fact sheets include seed source links to companies
selling seed. Access the Switchgrass
fact sheet and seed sources.
You can also call your local Natural Resources Conservation
Service or Cooperative Extension office to request recommendations
of seed dealers in your area. NRCS and Extension phone numbers
can be obtained in the Federal and County governments sections,
respectively, of your local telephone directory. Also, you can
access local NRCS and Extension directories on the following
Web sites: Natural
Resources Conservation Service Cooperative
Extension Service |
A word of caution. Planting switchgrass into cool
soils can be problematic from a weed standpoint. Cool season weeds
germinate first and can choke out switchgrass seedlings when the
soil warms. If cool season weeds are a concern, consider no-till
planting the switchgrass into a warmed soil with non-dormant seed.
Switchgrass seedlings can compete better in warmer soils when on
even footing with warm-season weeds.
A producer should expect slow switchgrass establishment even with
non-dormant seed and good planting management. As with most native
perennial grasses, switchgrass becomes fully productive only upon
the third year after planting.
Seed Dormancy. Switchgrass seeds can be very dormant
right out of the bag. A method to break dormancy ensures higher
rates of germination. Without a dormancy-breaking step in the planting
process, as few as five percent of the seeds may germinate. This
is thought to be one reason so many switchgrass and other native
warm-season plantings fail. To break dormancy, seeds can be wetted
and held at 41 to 50 degrees F for one month, then carefully re-dried.
This process is called stratification and is useful for small amounts
of seeds. There is risk of causing heat damage to the seeds during
drying, or causing premature germination of seeds, so small amounts
should be used until you become familiar with the method.
Photo courtesy of USDA-NRCS |
Another dormancy-breaking method is to plant seed with a drill
or no-till drill in winter or early spring. The cold temperatures
the seed will experience will stratify them and help to break dormancy.
Stratification can also be accomplished by frost-seeding in January
to March. Again, care should be taken when planting switchgrass
into cool soils due to cool-season weed pressure.
“After-ripening” is the dormancy-breaking practice
of storing seeds in a warm environment for several years. When combined
with no-till planting into a warm soil, it is one of the most effective
methods for establishing weed-resistant switchgrass stands
Weed Control. The establishment of warm-season
grasses is difficult not only because of seed dormancy, but also
because of competition from weeds. Perennial forbs and warm-season
grasses such as crabgrass germinate in cooler soils and can have
a severe impact on switchgrass stand establishment.
Switchgrass establishment can be improved by utilizing cultural
and mechanical control measures to reduce weed pressure. For instance,
annual cropping with small grains and field peas for one or two
years will provide an opportunity to control weeds several times
during the season while building soil organic matter. Also, nurse
crops can sometimes reduce weed pressure and provide a cash crop
in the form of hay, silage, or grain. Weeds can also be controlled
in newly planted switchgrass stands by mowing two or three times
during the growing season. Mow the weeds down to the tops of the
switchgrass plants so as to reduce the impact of defoliation on
the grass. Mowing can be effective against annual weeds especially
as they mature but prior to seed set. Mowing can also reduce perennial
weeds by effectively depleting root reserves by successive mowings
when the plant is at the boot stage.
Fertility. Most research on switchgrass fertility
has focused on its use as a forage. Grazing livestock require protein,
and higher nitrogen (N) applications can ensure not only high yields
but better quality feed. Some researchers have therefore considered
nitrogen fertilizer recommendations for switchgrass to be much higher
than necessary for biomass (i.e. cellulose) production.
Switchgrass, as a native perennial grass of the North American
tall-grass prairie, evolved in symbiosis with many other ecological
factors, including grazing, fire, nitrogen-fixing legumes and other
forbs, and soil microorganisms including bacteria and fungi. Many
scientists now believe that soil microbes play a major role in nutrient
uptake. For example, micro-fungi (mycorrhizae) are thought to play
an important role in phosphorus uptake. These microbes are a natural
constituent in native grassland soils.
A review of the literature suggests that switchgrass can be grown
on soils of moderate fertility without fertilizing, or with limited
additions of fertilizer, and still maintain productivity.
(Parrish
and Fike, 2005) Nitrogen and carbon naturally cycle from shoots
to below-ground parts (roots) at the end of the growing season as
a nutrient-conserving strategy. Prairie systems will gain nitrogen
from the atmosphere at a rate of 2 to 10 pounds per acre per year.
In addition, there is a reserve of nitrogen in the soil that can
be mineralized and made available for plant growth. The addition
of this nitrogen is a result of root death, leaf and stem death,
and nutrient cycling from the urine and feces of grazing animals.
Nitrogen-fixing legumes can also contribute to nitrogen
availability in the range of 50 to 150 pounds per acre per year,
depending on the species and percent composition of legumes in the
field.
Photo courtesy of USDA-NRCS |
Switchgrass for biomass should be harvested once per year, in the
winter. Under good management, a producer can expect a yield of
1 to 16 tons per acre. According to the Agricultural Research Service,
yields in the Southeastern U.S. range from 7 to 16 tons per acre,
and from 5 to 6 tons per acre in the western Corn Belt, while yields
in the northern plains are typically more modest at 1 to 4 tons
per acre. (Comis, 2006) If the protein composition
at harvest is 2 percent, and assuming a yield of 6 tons per acre,
approximately 38 pounds of nitrogen are harvested per acre. This
nitrogen must somehow be replaced or recycled to maintain productivity.
Nitrogen can be added into the switchgrass agroecosystem by:
- maintaining a legume component of at least 30 percent in the stand;
- adding 2 to 3 tons of manure per acre broadcast after harvest;
- incorporating manure in the fall prior to planting; or
- using synthetic fertilizers judiciously.
Incorporating legumes into a
switchgrass stand can be problematic from an ethanol feedstock quality
perspective, but not necessarily so if the biomass is dried and
used in direct combustion. If synthetics are used, the producer
should remember that low rates will provide excellent biomass yields.
Yearly applications of no more that 50 pounds per acre should be
appropriate.
It is very important to remember, though, that switchgrass has
a remarkable ability to extract nitrogen from unfertilized soils.
Parrish and Fike (2005) report a study where
a field was harvested for seven years with no fertilizer applications,
and averaged 53 pounds of N removed per year with one harvest per
year. Clearly switchgrass, a native prairie grass, has the genetic
ability to survive and produce with minimal if not zero inputs.
Companion Crops. Some farmers use companion or
“nurse crops” in establishing perennial crops such as
alfalfa and grass pastures and hayfields. An ideal nurse crop will
grow more quickly than the crop it accompanies and will provide
plant cover for the soil. Nurse crops must be removed early enough
to allow the protected crop to grow unhindered. Nurse crops are
often used on slopes to prevent water erosion and on level ground
to prevent wind erosion and seedling desiccation. A nurse crop that
has been used successfully in establishing switchgrass is sorghum-sudangrass.
Sorghum-sudangrass is a warm-season annual grass that is used for
grazing, hay, or silage. It is fast-growing in warm regions, broadleaved,
and of excellent forage quality when harvested at the right time,
which is just around panicle emergence. Other companion crops to
consider would be corn, spring planted wheat, triticale, or annual
ryegrass. These crops could be planted early in the spring, followed
by seeding of switchgrass between the rows. Plant switchgrass into
companion crops prior to crop emergence or when growth is still
low enough to permit a drill and packer wheels without damaging
the crop.
Harvesting. Switchgrass should be harvested with
conventional haying equipment after the top growth has completely
died back. This will occur from mid- to late October in most regions.
Several studies have found that a single harvest of switchgrass
from late fall or early winter results in the highest sustainable
biomass yields and good stand persistence from year to year. (Parrish
and Fike, 2005) Moisture should be 15 percent or less to facilitate
quick baling and transport, and to ensure a higher quality feedstock.
Switchgrass that is co-fired in coal plants is burned at a moisture
percentage of 12 to 13 percent. Contact the processing plant to
determine the size of bale they will accept. Many research programs
have utilized large rectangular bales (3 x 4 x 8 feet) with some
success, as these are easier to transport than small squares. Be
sure to leave about a 6-inch stubble after harvest. Forage research
has shown that leaving stubble helps to trap snow, thereby protecting
the root crowns from winter kill.
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Ecological Considerations: Prairies
and Farmscapes
Switchgrass, formerly a natural part of the prairie ecology of
North America, may contribute to more stable agricultural systems.
This assumes that switchgrass fields are inherently stable, beneficial
to wildlife, and sufficiently productive to offer incentives to
farmers to cultivate it. Switchgrass is deep-rooted, very efficient
at using nitrogen, and is thought to maintain a symbiotic or beneficial
relationship with microscopic soil fungi, which make soil nutrients
available to the extensive switchgrass root system. Switchgrass
is an excellent plant to use in riparian buffer strips or on other
sensitive lands, as its root system prevents erosion while slowing
the travel of surface water, decreasing run-off from agricultural
fields, and allowing for greater water infiltration.
Annual cropping, such as is done with corn, soybeans, and small
grains results in loss of soil organic matter and release of soil
carbon, whereas perennial crops can build soil organic matter and
are thought to store more soil carbon due to the large amount of
underground biomass they produce and maintain throughout the year.
Switchgrass is generally planted as a monoculture (a field
planted to only one species, such as corn, alfalfa, or soybeans),
either as a forage crop or a feedstock. Yield data have been developed
by studying monoculture stands, and pure stands are thought to yield
the highest quality feedstock for biofuels production (see Feedstock
Quality section below). Monocultural production is thought to
be problematic by many farmers and advocates of a more sustainable
agriculture. Monocultures are generally not as resilient as polycultures,
or fields planted to more than one species. Diverse plants occupy
more niches and better use soil and water resources both above and
below the soil surface. Biodiversity also provides food and cover
for numerous beneficial organisms, from microbes to earthworms,
to insects and small mammals. A diverse agricultural system mimics
the complexity of nature, and fosters an ecological balance that
some farmers have come to rely on to lessen the severity of pest
problems as well as build soil fertility by allowing for natural
nutrient cycling to occur.
The natural, native tall-grass prairie of North America was not,
of course, a monoculture. Many grasses, legumes, forbs, and shrubs
contributed to this complex and stable plant and animal community.
This is important to remember, because a monoculture of switchgrass
will never promise the same ecological benefits as a naturally diverse
prairie. That being said, pure switchgrass stands still have significant
benefits, especially for fields that have been cropped annually
and are experiencing degradation due to erosion and depleted soil
organic matter. A perennial grass stand offers nesting for birds,
helps to sequester soil carbon, builds soil organic matter, and
increases the efficiency of the water cycle. Since a switchgrass
stand can have an effective lifespan of well over 15 years, it might
find a place in long rotations to build soil and renovate infertile
farmlands.
Prairie Polycultures for Biofuel Feedstock?
Switchgrass has been studied as a monoculture for the production
of ethanol feedstock. One area that could possibly be studied
by agronomists and agricultural engineers is the use of diverse
prairie polycultures for biofuel production and their effect
on ethanol feedstock quality. Another area to investigate would
be the efficiency of polyculture feedstocks as a direct combustion
fuel for energy generation, which could be especially useful
for enhancing the sustainability of cellulosic ethanol plants. |
Feedstock Quality
Producers who are experienced at growing grasses for livestock
forage will find that producing switchgrass as an ethanol feedstock
necessitates a management regime unlike that utilized to produce
quality forages. High-quality ethanol feedstock is low in nitrogen
content and high in cellulose. Cellulose is broken down either by
an acid or enzymes into fermentable sugars prior to fermentation.
Nitrogen reduces the conversion efficiency of fuels into energy
and can become an air pollutant after combustion. Therefore, zero
or low fertilizer nitrogen applications and a single yearly harvest
after the plants have died back fully in the winter produce the
best feedstock, as well as the highest amount of above-ground biomass,
for ethanol production.
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Economics and Multiple
Uses of Switchgrass
The most important economic considerations in the production of
switchgrass are (1) yield, (2) land costs, and (3) the prices of
other feedstocks for biofuel production. Maintaining high yields
and keeping costs low result in the best economic returns in recent
switchgrass research projects. Another way to reduce costs and increase
farm productivity is to consider multiple uses such as grazing and
biomass production. Switchgrass is nutritious if grazed prior to
the boot stage of development, and is used as a livestock forage
by some graziers from the South to the Midwest. In order to obtain
both optimum livestock forage and biomass tonnage, graze the switchgrass
to no less than 6 inches in the spring and or early summer, and
allow the grass to regrow for a late fall or winter biomass harvest.
Switchgrass stands tend to decline over the years with more frequent
defoliation events (grazing, haying, or biomass harvest), so careful
attention to timing of harvest, number of harvests, and regrowth
is crucially important.
Case Study: The
Chariton Valley Biomass Project
The Chariton Valley Biomass Project is a Chariton Valley RC&D
managed project that is funded by the U.S. Department of Energy,
the U.S. Department of Agriculture, and Alliant Energy, among
others. In the spring of 2006 the project conducted a three-month
test burn of switchgrass at a coal-fired station in Iowa, and
has yielded some promising results.
The project involved over 31 thousand bales of Iowa-grown switchgrass,
totaling more than 15 thousand tons of biomass fuel. The switchgrass
fuel generated more than 19 million kilowatt hours of electricity,
which can meet the electrical energy needs of more than 1,800
homes for one year. During the burn, sulfur emissions were reduced
by 62 tons and CO2 was reduced by over 50 thousand tons. The
switchgrass used in this test burn replaced over 12 thousand
tons of Wyoming coal with a locally produced, renewable fuel.
Switchgrass can be co-fired in coal plants for electrical energy
generation, or combusted in ethanol plants for the production
of cellulosic ethanol. The Chariton Valley test burn exemplifies
the applicability of this new technology, and helps us to focus
on building greater efficiencies into renewable energy technologies,
with the goal of making them cost effective, affordable, and
sustainable.
Source: RenewableEnergyAccess.com |
Switchgrass for biofuel production has been considered for use
on Conservation Reserve Program (CRP) land in the more erodible
regions of the tall-grass prairie states. Compared to annual cropping
in these areas, switchgrass for biofuels could increase the ecological
sustainability of the prairies while lowering the cost of the CRP
program. However, CRP rules would have to be substantially modified
to allow such an economic use of CRP lands. Consideration of the
wildlife impacts of economic harvesting of CRP would also become
an important consideration as an important part of the continued
support for CRP has been its documented benefits to wildlife.
Cost Variables in Switchgrass Production
A short list of items to consider in calculating the cost of
producing switchgrass…
- Land—rent, land payments, taxes, opportunity cost
- Establishment—fuel, seeds, tillage and planting equipment, weed control, fertility, labor
- Crop maintenance—weed control, equipment repair, fertility, labor, etc.
- Harvest—equipment, fuel, baling materials, labor
- Transport—fuel, equipment, custom hauling, storage loss, labor
|
The CRP program is jointly administered by the USDA Farm Service
Agency (FSA) and the Natural Resources and Conservation Service
(NRCS), and once land is entered into the program there are limitations
on how it can be used. Your local FSA or NRCS office can provide
you with more information on CRP and the applicability of biomass
production on CRP lands.
Researcher David Bransby’s test plots of switchgrass at Auburn
University have produced up to 15 tons of dry biomass per acre,
with a six-year yield average of 11.5 tons per acre. Figuring roughly
100 gallons of ethanol produced per ton of feedstock, these switchgrass
yields are enough to make 1,150 gallons of ethanol per acre each
year (Biofuels from Switchgrass: Greener Energy Pastures,
Oak Ridge National Laboratory, Tennessee). Corn ethanol feedstocks
cost ethanol producers an estimated 40 to 53 cents per gallon of
ethanol produced. Switchgrass feedstock costs per gallon of ethanol
produced would need to be low enough (less than 40 cents per gallon)
to at least compete with corn ethanol to make cellulosic ethanol
production a cost-effective fuel. Currently, cellulosic feedstock
costs per gallon of ethanol produced are much higher than for corn
ethanol.
It is important to remember that the switchgrass market is still
very immature, and much work needs to be done to understand the
costs of conversions and development of local processing plants
and marketing outlets. To learn more about marketing switchgrass
for biofuel production, see the References and Resources
section at the end of this paper.
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Other Cellulosic Feedstocks
Switchgrass is not the only or possibly even the best biomass species
for cellulosic ethanol production, but it does possess some ecological
characteristics that make it a very good candidate. Among its positive
qualities, switchgrass offers:
- pest and disease resistance,
- high yields of cellulose,
- low fertility needs,
- cultivars that are locally adapted and relatively available,
- excellent wildlife habitat,
- carbon sequestration in its extensive and very deep root system,
- tolerance of poor soils and wide variations of soil pH,
- drought and flood tolerance (depending on the ecotype and variety),
and
- efficient water use in grassland ecosystems.
But many other perennial warm-season grasses may possess these
same characteristics and more. What makes switchgrass particularly
suitable as an ethanol feedstock? In research trials beginning in
the mid-1980s, the Department of Energy began to seek plant species
that would yield high quality and quantity biofuel feedstocks. Among
the plants considered were reed canarygrass and switchgrass, among
some other grasses and legumes. In the trials, switchgrass had the
highest yields and breeding work was subsequently focused on switchgrass
to the exclusion of the others.
Other sources of cellulosic feedstock under investigation are forest
residue, wheat straw, corn stover (leaves, stalks and cobs), rice
straw, and bagasse (sugar cane waste), other crop residues, municipal
solid wastes, poplar, and willow trees. David Bransby of Auburn
University suggests that, while ethanol will not be able to completely
replace fossil fuels for transportation and electricity, the diversity
of cellulosic feedstock materials available can go a long way to
increasing our energy independence by making cellulosic ethanol
more attainable. Coupled with conservation, biomass fuels can provide
for a portion of U.S. energy needs.
External technical review for this publication was provided
by David Parrish, Crop and Soil Environmental Sciences, Virginia
Tech, and Alan Teel, Iowa State University Extension, retired. |
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References and Resources
Agricultural Marketing Resource Center, the National Information
Resource for Value-Added Agriculture. Switchgrass
Web site.
Comis, D. 2006. Switching to Switchgrass
makes Sense, in Agricultural Research, July. USDA-ARS. www.ars.usda.gov/is/AR/archive/jul06/grass0706.pdf
(PDF / 234 K)
Costs of Producing Switchgrass for Biomass in Southern Iowa, Iowa
State University Extension Publication PM 1866. www.extension.iastate.edu/Publications/PM1866.pdf
(PDF / 384 K)
Farm Energy Resources
from ATTRA
National Sustainable Agriculture Information Service
800-346-9140 (English)
800-411-3222 (Español)
Greer, D. 2005. Creating
Cellulosic Ethanol: Spinning Straw into Fuel, in BioCycle, May
2005 eNews Bulletin.
Greene, N. 2004. Growing Energy: How Biofuels Can Help End America’s
Oil Dependence. New York: National Resources Defense Council. www.nrdc.org/air/energy/biofuels/biofuels.pdf
(PDF / 1.2 M)
Henning, J.C. 1993. Big
Bluestem, Indiangrass and Switchgrass. Department of Agronomy,
University of Missouri.
Iowa Department of Natural Resources, Switchgrass Program. www.iowadnr.com/energy/renewable/switchgrass.html
McLaughlin, S., J. Bouton, D. Bransby, B. Conger, W. Ocumpaugh,
D. Parrish, C. Taliaferro, K. Vogal, and S. Wullschleger. 1999.
Developing
Switchgrass as a Bioenergy Crop, in Perspectives on new crops
and new uses. J. Janick (ed.), Alexandria, VA: ASHS Press.
Morris, D. 2005. The
Carbohydrate Economy, Biofuels and the Net Energy Debate
(PDF
/ 1.2M). Minneapolis: Institute for Local Self-Reliance.
Oak Ridge National Laboratory. No date. Biofuels
from Switchgrass: Greener Energy Pastures. Oak Ridge, TN: Bioenergy
Feedstock Development Program. Accessed July 31, 2006.
Oregon State University. 2006.
Forage Information
System. Accessed May 24, 2006.
Parrish, D.J. and J.H. Fike.
2005. The Biology and Agronomy of Switchgrass for Biofuels, in Critical
Reviews in Plant Sciences, 24:423-459.
Pimentel, D. and T.W. Patzek. 2005. Ethanol Production Using Corn,
Switchgrass, and Wood; Biodiesel Production Using Soybean and Sunflower,
in Natural Resources Research, Vol. 14, No.1, March.
Renewable Energy Access.com. 2006. Switchgrass
Burn Test Proves Hopeful.
Accessed July 17, 2006.
Teel, A. and S. Barnhart. 2003. Switchgrass
Seeding Recommendations for the Production of Biomass Fuel in Southern
Iowa (PDF / 112 K). Iowa State University Extension.
Teel, A., S. Barnhart, and G. Miller. 2003. Management
Guide for the Production of Switchgrass for Biomass Fuel in Southern
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Vogel, K., and R. Masters. 1998.
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Switchgrass as a Bioenergy Crop
By Lee Rinehart
NCAT Agriculture Specialist
Tiffany Nitschke, HTML Production
IP302
Slot 297
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