ARS | Publication request: Sugar/Energy Canes as Feedstocks for the Biofuels Industry

Submitted to: Meeting Abstract
Publication Type: Abstract
Publication Acceptance Date: June 20, 2008
Publication Date: August 20, 2008
Citation: Richard Jr, E.P., Tew, T.L., Cobill, R.M., Hale, A.L. 2008. Sugar/Energy Canes as Feedstocks for the Biofuels Industry. Proc. Short Rotational Crops International Conference, August 19-21, 2008, Bloomington, Minnesota. p. 47.

Technical Abstract: Corn is the principle feedstock used for the production of ethanol in the U.S. Yields of corn and the cost of production differ among regions of the U.S. with yields in the South generally being lower and cost of production higher. Hence, identification of alternative agronomic crops for the production of biofuels would be particularly beneficial in the South. It is widely acknowledged that technologies for the conversion of the ligno-cellulosic component of the plant will have to be developed if the U.S. is to replace some of its needs for transportation fuel with renewable sources of biofuels. Sugar cane is cultured as a perennial row crop in the southern areas of Florida, Louisiana, and Texas. It has been grown, harvested, and processed for commercial sugar recovery in Louisiana since 1795, which lies further from the equator than almost any area where this tropical crop is grown. Sugar cane is a very efficient C4 grass in converting sunlight and other inputs into biomass ¿ biomass that includes a high percentage of sugar that can be easily converted to ethanol as demonstrated by the successes in Brazil. Three sugar cane varieties (L 79-1002, HoCP 91-552, and Ho 00-961), dropped from the sugar cane varietal development program because of excessive fiber levels, were released in 2007 as ¿bench-marking energy cane varieties¿ to meet the possible needs of biorefineries where the production of ethanol from all of the above-ground components of the crop is the desired objective The three varieties, produced soluble sugar yields of 10.5 to 14.8 t/ha and dry fiber (bagasse) yields of 13.0 to 20.8 t/ha with an estimated total ethanol yield of 11,400 to 13,400 L/ha when averaged over four yearly fall harvests of the same planting. New varieties of dedicated energy canes with higher levels of cold tolerance and higher fiber yields are being developed by introgressing genes from sugar cane¿s wild relative, Saccharum spontaneum, and from its near relatives Miscanthus and Erianthus in an attempt to move the geographic range of adaption further northward. Some of these early generation hybrids are being tested in Alabama, Arkansas, California, Mississippi, and Oklahoma, as well as more northern areas of the traditional cane growing states. Other types of sugar-containing grasses are also being evaluated as complimentary crops to lengthen the season for feedstock deliveries and reduce storage costs at the biorefinery. Among these are four sweet sorghum varieties (Dale, M 81-E, Theis, and Topper) and two essentially non-flowering sorghum x sudangrass forage hybrids (MMR 333/27 and MMR 333/47). When planted in the early spring and harvested in the mid- to late-summer prior to sugar cane harvest (approximately 140 days after planting), soluble sugar and dry biomass yields of 8.1 and 15.7 Mg/ha were obtained with estimated total (sugar plus fiber) ethanol yields averaging 11,300 and 11,200 L/ha for the sweet and forage sorghums, respectively. Of the total ethanol produced, 50% of the sweet sorghum¿s ethanol yield was derived from sugar while for the forage sorghums only 34% was produced from sugar. Both the energy canes and the sweet and forage sorghums can be harvested with conventional sugar cane harvesting equipment and should be adaptable to a larger area of the South.