Switchgrass (Panicum virgatum
L.)
Switchgrass is a warm season perennial grass of the millet family. It was a component
of the native prairie in southern Manitoba and southeastern Saskatchewan. Switchgrass
propagates by rhizomes and seeds produced from the panicle head with one small head seed
being produced per spikelet. Switchgrass grown from seed has low vigor and is slow to
establish with production decreased until the third year after seeding. Once established,
switchgrass prefers low-lying mist light loam soils and is tolerant of flooding. Being a
warm season grass the majority of growth will occur during the warm summer months of June,
July and early August under Manitoba conditions.
As a pasture forage, switchgrass is palatable in the vegetative stage but is often
grassed out of mixtures as it is not tolerant of close and continuous grazing. Switchgrass
can produce reasonable hay yields under a one-cut-per-year system (Campbell, Best and
Budd, 1956).
Switchgrass as a Biofuel
Interest in switchgrass as a biofuel is based on its warm season growth habit and high
yields. The C4 photosynthetic pathway allows for improved water use efficiency during its
period of growth; this results in a lower silica and chloride content than cool season
grasses contributing to a lower ash content. Combustion of switchgrass pellets has been
observed to result in newly complete combustion with only 3% to 4% of original mass remaining
as ash following combustion in a pellet stove when switchgrass is overwintered in the
field.
Ash contents can be further reduced by allowing the switchgrass to overwinter in the
field, thereby reducing the silica and chloride contents further through the process of
leaching. There are also advantages from an ash content perspective to producing
switchgrass in sandy soils and opposed to clay soils, again based on silica and chloride
contents. REAP data indicates yield losses of ¼ to 1/3 as a result of overwintering.
Switchgrass has been observed in Manitoba by researchers at AAFC Brandon, they observed
switchgrass yields using over a period of four years from 1993 to 1996 at a clay and sandy
site, data shown in Table 1.
Table 1. Swtichgrass yields at clay and sandy sites over
four years
|
Year |
Clay
Kg/ha (lbs/acre) |
Sand
Kg/ha (lbs/acre) |
|
1993 |
1620 (1445) |
2150 (1918) |
|
1994 |
7370 (6574) |
3646 (3252) |
|
1995 |
8753 (7808) |
2567 (2290) |
|
1996 |
6671 (5950) |
2603 (2322) |
Manitoba Agriculture, Food and Rural Initiatives staff currently have switchgrass established in forage
demonstration plots located at Melita and Killarney. These plots yielded 4302 kg/ha (3840
lbs/acre) at Melita and 5759 kg/ha (5140 lbs/acre) at the Killarney site.
Fuel Value of Switchgrass
It has been estimated (Roger Samson, Pers. Com.) that switchgrass pellets can be
produced and marketed for a price of $150/MT. This price could include $50/MT paid to
switchgrass producers for new baled switchgrass product, $50 for transportation and
pellets, and $50 for packaging and marketing of the pellets. Switchgrass pellets have been
observed to produce in the size of 18.5 GJ/MT for late fall harvested switchgrass and 19.2
GJ/MT for overwinter switchgrass. As a comparison wood has been reasoned as producing 19.8
GJ/MT and wheat straw at 19 GJ/MT. If a final pelleted price of $150/MT is considered,
switchgrass pellets as source of energy would cost in the range of $7 to
$8 per GJ. Furthermore,
if a comparison energy source of natural gas is priced at $17/GT (late January price
according to energyshop.com), then it has been estimated that
an average homeowner would recoup the costs of a pellet stove purchase in
three
to four years (based
on pellet stove price of approximately $3000 Cdn).
Energy Price Information
Natural gas prices have spiked to record levels in
the past 12 months. Prior to December 1999, natural gas prices have
hovered between $1 and $3/GJ since 1996.
January 2001 prices for natural gas reach $17/GJ and have dropped since then to
approximately $8/GJ. Certainly the long term prospective for biofuels as an energy source
needs to consider the economic value for the alternatives in the energy market. Energy can
be produced from switchgrass for from $7 to $8/GJ, this must be considered the basement price
for natural gas below which switchgrass as an energy source will not be feasible. CIBC
Investor Services have forecasted crude oil prices to drop to an average of $24/bbl in
2001 and $22/bbl in 2002 from highs of greater than $30/bbl in 2000. In contrast to this,
energyshop.com forecasts natural gas prices to
return $14/GJ or $0.50/m3 by the end of 2002.
Conclusion
Biofuel production presents an alternative outlet for fiber production from prairie
agriculture. The traditional sources of energy must be considered the base from which the
economic value of these biofuels is priced. As time passes and traditional energy sources
become more expensive, biofuels may gain in importance, as they become more cost
competitive. Producers of biofuels are likely to be the first to take advantage of these
opportunities due to their lower GP relative to lower temperature costs and on-farm use.
With the most recent natural gas prices quoted in the range of $7 to $8/GJ, it is doubtful
that switchgrass will become a significant energy source for homeowners in the near
future.
Unfortunately, switchgrass pellets are not
available in Manitoba to-date; however numerous private companies
have begun working on developing the technology to change this. And
if you do find switchgrass pellets, it is not recommended to use
them in your wood pellet stove. However, there are some fiber blends
that may contain grass-based fibers that can be burned in your wood
stoves.
Source:
Campbell J.D, K. F. Best, A.C. 1956. Budd 99 Range Forage Plants of the
Calm Prairies. Ottawa: Canada Dept. of Agriculture. |
