Switchgrass as a Biofuel: Is it Economically Feasible?

Background

With increasing costs for energy prices over the last 12 months (see energyshop.com) many homeowners are interested in alternative energy sources for home heating. This, combined with lower commodity prices in recent years, has resulted in interest from producers for alternative crops to produce an economic return. The concept of using agricultural fiber for direct combustion as a heating source has been proposed as a potential solution to these issues. Agricultural fiber is a potential source of energy that can been pelletized through conventional pelleting plants and burned in pellet stoves to heat homes.

Switchgrass in particular has attracted attention as a fiber source for biofuel since it will typically result in lower ash content that other fiber sources.

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

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.