Tropical Maize As an Alternative Biofuel or Silage Crop.

With increasing world population, the U.S. Department of Energy initiated the Energy Independence and Security Act (EISA) requiring by 2030 the replacement of 30% of petroleum based fuel sources with biofuel. Tropical maize (Zea mays L.) is a promising new biofuel crop for the Midwestern US. It is a temperate by tropical (or tropical by tropical) hybrid that retains the photo-period sensitivity of tropical materials when grown in temperate regions, resulting in delayed flowering and high biomass, but with reduced grain production. The reduced grain production results in the accumulation of sucrose in the stalk and a lower nitrogen requirement. Our objectives were to evaluate the potential of tropical maize as a biofuel, biomass, or animal feed crop, and to assess its need for fertilizer N. Tropical maize hybrids have been characterized as: 1) dual-purpose producing high biomass levels with high quality grain yield that can be harvested for grain and the stover used in a bale-burning furnace for thermal energy, or that can be ensiled for use as animal feed; and 2) high sugar that produces high biomass and high stalk sugar accumulation that can be used for ethanol production. The experiment was conducted in Champaign, IL in 2013. The two hybrid types were evaluated under two nitrogen rates of 0 and 135 kg N ha^-1, and whole plant samples were taken at two harvest dates to determine total above ground biomass, and sugar accumulation. With and without supplemental N, the high sugar hybrid yielded an above-ground biomass of 15.8-18.2 Mg ha^-1 and the dual-purpose hybrid 15.6-21.0 Mg ha^-1 which are comparable to yields of switchgrass and miscanthus. Theoretical ethanol production that could be produced from the total above-ground biomass was equivalent to that of modern grain hybrids, but with a lower requirement for fertilizer N. Work in 2014 is further evaluating the potential of tropical maize as a high-energy biofuel or a feed crop.