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The higher productivity of the bioenergy feedstock Miscanthus x giganteus relative to Panicum virgatum is seen both into the long term and beyond Illinois

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Title: The higher productivity of the bioenergy feedstock Miscanthus x giganteus relative to Panicum virgatum is seen both into the long term and beyond Illinois
Author(s): Arundale, Rebecca
Director of Research: Long, Stephen P.
Doctoral Committee Chair(s): Long, Stephen P.
Doctoral Committee Member(s): Voigt, Thomas B.; Ort, Donald R.; Ming, Ray; Davis, Sarah C.
Department / Program: Plant Biology
Discipline: Plant Biology
Degree Granting Institution: University of Illinois at Urbana-Champaign
Degree: Ph.D.
Genre: Dissertation
Subject(s): Miscanthus x giganteus Panicum virgatum bioenergy feedstocks agronomy composition nitrogen yield biofuels
Abstract: Bioenergy crops provide a potentially carbon neutral, secure and abundant alternative to fossil fuels. To understand the land areas needed to achieve bioenergy at scale, primary information on the comparative productivity and sustainability of potential feedstocks in time and space is critical. Two C4 perennial grasses, Miscanthus x giganteus and Panicum virgatum (switchgrass), have both been promoted as productive low-input and sustainable feedstocks for the U.S. Comparative information on yield, fertilizer requirements and feedstock quality of these two has not been available either in the long-term (>5 years) or across a wide geography in North America. This dissertation addresses these key gaps, by four studies: 1) The first long-term side-by-side yield trials of M. x giganteus and P. virgatum extending over six to eight consecutive annual harvests at seven locations in the U.S. Midwest. M. x giganteus continually produced yields more than twice that of P. virgatum, 23.4 ± 1.2 Mg ha-1 y-1 and 10.0 ± 0.09 Mg ha-1 y-1, respectively. However, yields of both M. x giganteus and P. virgatum decline with stand age in Midwestern USA, which will require revision of the land area needed for both species to reach national cellulosic ethanol targets. 2) A split-plot nitrogen fertilization study (0, 67, 134, 202 kg N ha-1) performed over three to four years on mature stands of M. x giganteus and P. virgatum at seven locations in the U.S. Midwest, the first ever to directly compare the effect of nitrogen fertilizer on these two species. Nitrogen fertilization significantly increases yields of stands of M. x giganteus and P. virgatum in multi-year trials in Illinois. M. x giganteus increased from 23.4 Mg ha-1 without nitrogen fertilization to 28.9 Mg ha-1 (+ 25%) at 202 kg N ha-1 and P. virgatum yield increased from 10.33 Mg ha-1 to 13.6 Mg ha-1 (+ 32%). The gain from nitrogen fertilization was small compared to gains in annual grain crops, while substantial yields were obtained without any N fertilization. 3) Variation in cellulose, hemicellulose, lignin, acetyl, ash, and extractables at seven locations of varied soil types, with four nitrogen fertilization levels, and pre- and post-senescence sampling on a single genotype of M. x giganteus. Nitrogen fertilization did significantly decrease the proportion of hemicellulose, acetyl, and ash and increased cellulose, lignin, and biomass yield. Delaying harvest from October to December significantly increased the proportion of cellulose, hemicellulose, and lignin and decreased the proportion of ash and extractables. Overall, biochemical composition varied remarkably little and the results show that a uniform feedstock could be obtained across a region despite environmental variation, if a genetically uniform feedstock is used. 4) Establishment and yield of M. x giganteus and varieties of P. virgatum was tested in side-by-side trials at 10 locations in the eastern U.S. (GA, IL, KY, LA, MI, MS, NJ, OK, SD, WI) and one in Ontario, Canada. Establishment was very successful for both species at all sites. Yields at three years, when the crops are considered mature, averaged 12.9 Mg ha-1 for M. x giganteus and 10.8 Mg ha-1 for P. virgatum. While significantly higher for M. x giganteus, the difference is smaller than expected from prior studies, and suggests that to meet the national cellulosic ethanol mandate 27 million hectares of land may be needed rather than the previously predicted 12 million hectares. This project provides the first long-term comparison of M. x giganteus to P. virgatum for bioenergy production in the U.S. Midwest. This work concludes that high yields can be maintained in the long-term with minimal inputs and the nitrogen response of M. x giganteus is similar to that of P. virgatum. Furthermore, this works shows that a suitable and consistent lignocellulosic biomass feedstock is obtained from M. x giganteus. Finally this project demonstrates that both M. x giganteus and P. virgatum can be successfully established across a broad geographic range and that high yields are obtained throughout this range. Growth of M. x giganteus and P. virgatum for long-term production of lignocellulosic energy is viable choice to reduce carbon emissions relative to conventional fossil fuels.
Issue Date: 2012-09-18
URI: http://hdl.handle.net/2142/34422
Rights Information: Copyright 2012 Rebecca Arundale
Date Available in IDEALS: 2012-09-18
Date Deposited: 2012-08
 

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