Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 17, 2012
Publication Date: N/A
Interpretive Summary: There has been increasing interest in how biorefineries producing energy from plant materials, known as biomass feedstock, will operate in the southern Great Plains. Much of this interest has been focused at the level of the refinery, not at the level of the producer of feedstock. We tested whether individual producers could economically produce feedstock using existing equipment and types of forages, and how this activity would fit within existing systems of management that combined grazing of cool-season pasture by stocker cattle, hay and grain production. We used the amount of fall and end of season forage produced by two cool-season perennial grasses, and forage and grain produced by pastures of winter wheat, during 2001 through 2006 to describe amounts of returns to different activities, and subtracted costs required to produce forage and grain to define net returns. We found that cool-season perennial grasses required farm gate prices of $60 to $70/ton to be economic feedstock, and would generate greater returns if producers used them for grazing stocker cattle. In contrast, straw baled following grain harvest of wheat, with or without fall grazing, would generate positive returns across feedstock values of $30 to $70/ton. Wheat straw had more value as feedstock because it provides value for materials that are a by-product of grain production, and spreads production costs over a wider range of activities. Pastures of perennial grasses, in contrast, must cover costs of production from a narrower range of activities. These results show that producers could provide biomass feedstock for energy production if the feedstock comes from diversified systems rather than single-purpose crops, particularly if biorefineries were interested in wheat straw.
Technical Abstract: Interest in producing biomass feedstock for biorefineries has increased in the southern Great Plains, though research has largely focused on the potential function of biorefineries. This study examined feedstock production from the producers’ viewpoint, and how this activity might function within different forage-grain-livestock systems. Fall and end of season forage and grain production was defined on paddocks (2.02 ha, n=36) of cool-season perennial grasses (‘Jose’ tall wheatgrass, Thinopyrum ponticum; ‘Manska’ intermediate wheatgrass, T. intermedium; ‘Lincoln’ smooth brome, Bromus inermis) and winter wheat (Triticum aestivum) in central Oklahoma (35º40’ N, 98º00’ W) during 2001 through 2006. Paddocks (n=9/forage) and sets of enclosures within paddocks received one of three levels of N fertilization during the growing season (45, 90 and 135 kg N/ha) to support grazing, hay, and grain production. Costs required to establish and operate paddocks were developed from databases, and returns generated by forages and grain were calculated and adjusted to 2002 values. Partial budgeting was used to compare the economic function of strategies combining fall grazing, forage, grain, and feedstock production. Wheatgrass paddocks generated positive returns with fall grazing and spring hay production combined, but generated negative returns as feedstock at values = USD 55/Mg. Straw harvested from wheat paddocks, combined with grain production with or without fall grazing, generated positive returns across the range of feedstock values tested (USD 33 to 77/Mg). Results indicate that full diversification to exploit residues of grain crops for biomass feedstock would benefit producers more than the less diversified systems available for use of cool-season perennial grasses.