Long-term biomass and potential ethanol yields of annual and perennial biofuel crops

TitleLong-term biomass and potential ethanol yields of annual and perennial biofuel crops
Publication TypeJournal Article
Year of Publication2019
AuthorsRoozeboom, KL, Wang, D, McGowan, AR, Propheter, JL, Staggenborg, SA, Rice, CW
JournalAgronomy Journal
Pagination74 - 83
Accession NumberKNZ001973

Although energy crops could eventually supply a growing portion of cellulosic biofuel feedstocks, long-term comparisons of annual and perennial crops are rare. An experiment was established in 2007 near Manhattan, KS, to compare biomass productivity and ethanol yield of perennial and annual crops. Perennial crops included three C4 grasses: switchgrass (Panicum virgatum L.), big bluestem (Andropogon gerardii Vitman), and miscanthus (Miscanthus sacchariflorus). Annual C4 crops were corn (Zea mays L.) in two rotations: continuous and rotated with soybean [Glycine max (L.) Merr.]; and five types of sorghum [Sorghum bicolor (L.) Moench]: photoperiod sensitive, sweet, dual purpose (grain and biomass), brown mid-rib, and grain; all rotated with soybean. Annual crops produced 7 Mg ha–1 yr–1 more biomass than perennial crops throughout 11 yr, with sweet sorghum exceeding 22 Mg ha–1 yr–1, and 12 m3 ha–1 yr–1 of ethanol. Biomass yield of miscanthus approached 14 Mg ha–1 yr–1, essentially the same as for several annual crops but with half as much fertilizer nitrogen. Annual ethanol production from miscanthus and switchgrass was 3.6 m3 ha–1 yr–1, half as much as that of several annual crops that produced similar biomass yields. Big bluestem consistently produced the least biomass and ethanol, less than 7 Mg ha–1 yr–1 and 1.7 m3 ha–1 yr–1, respectively. Rotated corn averaged 7.1 m3 ha–1 yr–1 of ethanol. Eleven years of results indicate that annual corn and sorghum crops as well as perennial grasses such as miscanthus and switchgrass could play a role as potential bioenergy feedstocks in diversified production systems.