Current U.S. plans for energy security rely on the conversion of large acreages from food crop production to the production of cellulosic biomass. To ensure the long-term sustainable production of biofuel, we are conducting comparative analyses of the productivity potential and the environmental impacts of the most promising biofuels crop species and management systems at Purdue University’s Water Quality Field Station (WQFS). Project team expertise combined with the unique WQFS capabilities for quantifying agro-ecosystem carbon (C), nitrogen (N) and water balance will permit a quantitative assessment of candidate system net energy balance. Our overall goal is to develop a cropping system-level analysis of the potential for Miscanthus, switchgrass, maize-based and low-input native prairie production systems to provide renewable fuel while protecting natural resources.
Our hypothesis is that candidate biofuel cropping systems differ in total yield and yield of structural and non-structural carbohydrate pools that determine profitability but that candidate systems also differ in water, N, and C economies; these differences will drive changes in soil, water and air quality that, in turn, determine the scope and nature of environmental impacts and sustainability. Specific objectives are to:
- determine the comparative environmental impacts of switchgrass, Miscanthus, maize (grain and grain plus stover removal), and low-input big bluestem including the assessment of: a) cropping system impact on soil storage (sequestration) of C and N; b) cropping system impact on nitrate and dissolved organic carbon edge-of-field loss to water as facilitated by artificial tile drainage, and c) cropping system impact on greenhouse gas emissions.
- determine the comparative biofuels feedstock potential of switchgrass, Miscanthus, maize (grain and grain plus stover removal), and low-input big bluestem including the assessment of: a) the quantity and quality (chemical composition) of feedstocks; b) the crop-specific nutrient use efficiency including uptake and physiological efficiency, and c) the crop-specific water balance.
Purdue University has unique capabilities with respect to the study of agro-ecology and the environmental costs and co-benefits of highly-productive, intensive agriculture. The WQFS is a highly-instrumented, field facility that includes 4 replicates of 12 cropping systems. At the core of each of the 48 treatment plots (10.8 x 48 m) is a 24 m x 9 m drainage lysimeter that is structured to permit a quantitative characterization of mass loss of soil constituents to surface water. Existing WQFS instrumentation also permits characterization of methane, carbon dioxide and nitrous oxide emissions from the soil surface. From 1995 to the present, 11 treatment plots have focused on maize and soybean production systems receiving different rates and sources (inorganic and manure) of fertilizer. One treatment plot has been continuously maintained as a native prairie. In spring 2007, several treatments were identified for conversion to biofuel production systems and establishment of these systems is ongoing. For the 2008 growing season, WQFS treatments included:
- Low-input big bluestem: a facsimile for the native prairie community with no fertilizer inputs
- Maize grown in rotation with soybean and fertilized according to university recommendations
- Continuous maize fertilized according to university recommendations with no residue removal
- Continuous maize fertilized according to university recommendations with residue removal at harvest
- Miscanthus production using best known management practices for establishment and maintenance
- Switchgrass production using best known management practices for establishment and maintenance
Trts. 1, 4, 5, 6 represent candidate biofuel systems, while Trts. 2, 3, and 4 are traditional food/feed systems that can also provide corn grain and soybean seed for ethanol and biodiesel, respectively.
Collectively, proposal PIs have expertise in soil microbial ecology, plant physiology and biochemistry, soil physics and chemistry, and ecology and have an established record of collaborative research in cropping systems and agro-ecology. While funding opportunities for research on the environmental aspects of biofuels are currently sparse, growing recognition of the myriad of potential, unintended consequences of biofuel production is expected to divert significant extramural funds to environmental research. Given the present dearth of information on biofuels and the environment, this project is creating a major, in-field demonstration of candidate system performance at a location and under conditions that typify the eastern cornbelt of the U.S. This effort enhances Purdue University’s partnership with the USDA-ARS National Soil Erosion Research Laboratory in pursuit of a common research agenda.
Impact of Project
Long-term sustainable biofuels production with the concomitant protection and improvement of air, soil and water resources requires a concerted effort by the scientific community to gain knowledge regarding the comparative production potentials and environmental impacts of biofuel cropping systems. U.S. agriculture has extensive experience with intensive maize production and much recent discussion on energy from plants has focused on simply repurposing the existing farming systems towards ethanol instead of or in addition to animal feed. Both the grain and the stover can be used in energy production but removing the majority of the aboveground biomass from a farm field may negatively impact air, soil, and water quality. Herbaceous perennials including novel species such as Miscanthus imported from Europe and low-input native systems may offer key advantages over maize production. Farmers can use existing farm equipment and these systems are expected to require far fewer energy and financial inputs than annual row crops. However, at present, research on N and C cycling in these candidate biomass systems is fragmented and incomplete, a critical barrier to profitable, sustainable, and environmentally benign on-farm implementation of the U.S. biofuel agenda. Likewise, understanding crop water balance and optimizing water use efficiency will be essential to renewable biofuel success as water is expected to be the single, most limiting factor that transcends the multiple agro-ecozones in which U.S. biofuel production will be pursued. Project results will provide critical baseline knowledge regarding the relevant production and environmental merits of candidate biofuel systems, knowledge also necessary for development of informed public policy.