Environmental Impact and Sustainability of Feedstock Production

Principal Investigator: Evan DeLucia, U of Illinois
Co-PIs: May Berenbuam, Carl Bernacchi, Mark David, Roderick Mackie
Postdocs: Tony Yannarell, Kristina Anderson-Teixeira, Sarah Davis, Candice Smith, Marcelo Zeri, Yuejian Mao, Xiangzhen Li, Saber Miresmailli
Graduate Students: Terry Harrison, George Hickman, Lisa Raetz, Joshua Burke, Paul Nabity, John Drake
Visiting Researcher: Michael Masters
Researchers: Corey Mitchell, Dorothy Feickert, Nicholas DeLucia, Michael DeLucia, Jeremy Pillow, Andrew Lovdahl, Daniel Pearlstein
Undergraduate Students: Anthony Duong, Samirah Ali, Keara Fanning, Michael Bolouri, Morgan Davis, Robert Orpet, Micah Sweeney, Christopher Novotney, Andrew Groll, Allen Lawrence, Alan Yanahan, Jaclyn Marganski, Gevan Behnke, Heather Grames, Matthew Rundquist, Lauren Segal, James Lee, Owen Cofie, Robert Lane
Faculty Collaborators: Arthur Zangerl, Robert Darmody
Subcontractor: William Parton

The widespread deployment of biofuel feedstocks may herald a new era for US agriculture; an era in which feedstock production and ecological impacts are balanced leading to a sustainable system.  Because of their high rates of biomass accumulation with minimal nutrient inputs, Miscanthus x giganteus, switchgrass (Panicum virgatum), and restored prairie hold great promise as potential feedstock crops in the US Midwest. Before the self-scouring steel plow, this region was expansive grassland with enormous stores of organic soil matter. The conversion of this vast grassland to row crop agriculture dominated by the soybean-corn rotation, depleted soil carbon, and nitrogen stores caused extensive soil erosion and contributed to pollution of surface and ground water primarily by nitrate derived from fertilizer. Because of their perennial growth habit, extended growing season, and low demand for nutrients, replacement of a portion of this corn-soybean landscape with feedstock crops has the potential to mitigate many of these environmental impacts. To date, there have been no side-by-comparisons of potential ecosystem impacts of feedstock crops with corn, also used in the production of cellulosic ethanol.

The objective of the proposed research is to quantify the major pools and fluxes in the biogeochemical cycles of carbon, nitrogen, and water in large plots of M. x giganteus, switchgrass, restored prairie, and corn, and to determine how and on what timescale interactions with soil microbial and insect populations affect these biogeochemical cycles. By “closing” the biogeochemical cycles of C, N, and water, we will develop a mechanistic understanding of how different feedstock crops affect major ecosystem services, such as the capacity to sequester atmospheric carbon, retain soil nitrogen, and minimize water contamination and the production of important greenhouse gases including methane and nitrous oxide.

Large replicated plots of M x giganteus, switchgrass, restored prairie (12 species), and continuous corn will be established at the UIUC Energy Farm. Each plot will be instrumented with a micrometeorological tower for measuring surface-atmosphere exchange of CO₂, water vapor, energy, N₂O, and methane.  Patterned tile drains under each plot will allow complete collection of drainage water from each vegetation type to quantify elemental and nutrient losses to leaching. Tissue specific measurements of material exchange, in some cases using stable isotope fractionation, will facilitate closure of the major biogeochemical cycles in each feedstock type. Above- and belowground herbivore damage and changes in the diversity and activity of the soil microbial communities will enable us to determine how soil processes, particularly rates of mineralization, nitrification, and denitrification, are regulated. We expect that the greatest dynamic differences in ecosystem processes between M. x giganteus, switchgrass, and restored prairie with corn to occur during the three-year establishment period leading to mature perennial communities. Data will be used to inform DAYCENT, a process-based model that will enable us to extrapolate our results regionally. A later phase of this research will examine climate interactions dominated by decreasing precipitation by examining ecosystem processes in feedstock plots distributed along a longitudinal gradient from Ohio to California.

This research will inform the broader biofuel and environmental communities of the potential ecosystem consequences and benefits of the extensive deployment of perennial feedstock crops in land currently supporting row-crop agriculture, and will guide efforts to reduce unforeseen negative impacts of these feedstocks.

2009 Program Update:
The objective of the program is to understand how the cultivation of biofuel crops would impact carbon, nitrogen, and hydrologic cycles. We are quantifying the major pools and fluxes of carbon, nitrogen and water in Miscanthus x giganteus, switchgrass, restored prairie, and corn, as well as determining the regulation of these fluxes by the insect and soil microbial communities. Preliminary measurements of changes in the isotopic composition of carbon in the soil, and gas and energy exchange between the land surface and the atmosphere for field plots at the Energy Farm and at different locations in Illinois, indicate that perennial feedstocks have the potential to restore soil organic carbon to levels existing before the expansion of annual row-crop agriculture, while simultaneously reducing losses of nitrate to ground water and nitrous oxide to the atmosphere. Early results indicate that changes in the soil microbial community associated with the transition of land previously in soy-corn rotation to perennial feedstocks is improving the capacity to retain nitrogen. Additionally, the vulnerability of above-ground biomass to herbivore losses is lower in perennial feedstocks than adjacent prairie. In potential contrast to improvements of the carbon and nitrogen cycle associated with converting land from annual row-crop agriculture to perennial feedstocks, preliminary results indicate that Miscanthus and switchgrass may be more water demanding that the soy-corn rotation. Early indicators suggest that the widespread deployment of perennial feedstocks may improve ecosystems services from land currently in annual row-crop agriculture. A major thrust over the next quarter will be to use our data to parameterize a process-based model to predict how changes in land use associated with an expanding biofuel enterprise will affect carbon and nitrogen biogeochemistry and hydrology of the Mississippi river watershed.