Article

Ecosystems

, Volume 13, Issue 1, pp 144-156

Comparative Biogeochemical Cycles of Bioenergy Crops Reveal Nitrogen-Fixation and Low Greenhouse Gas Emissions in a Miscanthus × giganteus Agro-Ecosystem

  • Sarah C. DavisAffiliated withInstitute of Genomic Biology, University of Illinois at Urbana-ChampaignDepartment of Plant Biology, University of Illinois at Urbana-Champaign
  • , William J. PartonAffiliated withNatural Resources and Ecology Laboratory, Colorado State University
  • , Frank G. DohlemanAffiliated withDepartment of Plant Biology, University of Illinois at Urbana-Champaign
  • , Candice M. SmithAffiliated withEnergy Biosciences Institute, University of Illinois at Urbana-Champaign
  • , Stephen Del GrossoAffiliated withUSDA Agricultural Research Service, Soil Plant Nutrient Research
  • , Angela D. KentAffiliated withEnergy Biosciences Institute, University of Illinois at Urbana-ChampaignDepartment of Natural Resources and Environmental Sciences, University of Illinois at Urbana-Champaign
  • , Evan H. DeLuciaAffiliated withInstitute of Genomic Biology, University of Illinois at Urbana-ChampaignDepartment of Plant Biology, University of Illinois at Urbana-ChampaignEnergy Biosciences Institute, University of Illinois at Urbana-Champaign Email author 

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Abstract

We evaluated the biogeochemical cycling and relative greenhouse gas (GHG) mitigation potential of proposed biofuel feedstock crops by modeling growth dynamics of Miscanthus × giganteus Greef et Deuter (miscanthus), Panicum virgatum L. (switchgrass), Zea mays L. (corn), and a mixed prairie community under identical field conditions. DAYCENT model simulations for miscanthus were parameterized with data from trial plots in Europe and Illinois, USA. Switchgrass, corn, and prairie ecosystems were simulated using parameters published in the literature. A previously unknown source of nitrogen (N) was necessary to balance the plant nutrient budget in miscanthus crops, leading us to hypothesize that miscanthus growth depends on N-fixation. We tested for nitrogenase activity by acetylene reduction of whole rhizomes and bacteria isolated from the rhizosphere and miscanthus tissue. Our results supported the hypothesis that biological N-fixation contributed to the N demand of miscanthus, a highly productive perennial grass. Corn agro-ecosystems emit 956 to 1899 g CO2eq m−2y−1 greater GHGs (including CO2, N2O, CH4) to the atmosphere than the other biofuel crop alternatives because of greater N2O emissions from fertilizer additions. Of the feedstock crops evaluated in this study, miscanthus would result in the greatest GHG reduction.

Keywords

biofuel bioenergy carbon sequestration cellulosic corn DAYCENT ethanol prairie switchgrass soil carbon