Issue At Hand

The US is embarking on an aggressive agenda to reduce dependency on fossil fuels. In response, the demand for feedstocks for liquid biofuels will continue to grow into the foreseeable future. While the Energy Independence and Security Act of 2007 acknowledges that grain-derived ethanol will meet much of the initial need, cellulosic materials (Fig. 1) are mandated to provide a growing portion of our bioenergy feedstocks. While such "second generation" feedstocks show numerous potential advantages compared to grain-based systems -- including reduced energy and nitrogen inputs, higher rates of energy return, greater soil carbon sequestration, and reduced greenhouse gas emissions -- it is unlikely that a single cellulosic biomass cropping system will meet all of these purposes in all agroecosystems. A portfolio approach is needed. Potential systems to be included in the bioenergy feedstock portfolio need to be developed, tested, and compared to conventional systems prior to their implementation over local, regional, and national scales.

Fig. 1 - Switchgrass, a potential cellulosic feedstock, being harvested for bioenergy production
(photo credit: John Sellers).

Fig. 2 - Hypothesized multifunctional (agronomic, economic, and environmental) performance of the experimental biomass cropping systems.

What We Expect to Accomplish

Our goal is to develop, refine, and implement a portfolio of sustainable bioenergy feedstock production systems that together contribute significantly to reducing dependence on foreign oil; have net positive social, environmental, and rural economic impacts; and are compatible with existing agricultural systems. To accomplish this goal, we are developing several alternative biomass cropping systems and comparing them to a conventional continuous corn system. Alternative cropping systems were chosen because of their potential to provide:

As crop performance is strongly tied to site factors, we are evaluating these biomass cropping systems across a series of landscape positions (Fig. 2). Our results will eventually allow for optimized bioenergy feedstock production across agricultural landscapes.

How We Go About It

Field and lab measurements evaluate and compare (1) energy/fertilizer inputs, (2) biomass outputs, (3) establishment, production, harvest, and transport costs, (4) water use and quality impacts, (5) above and belowground pools and fluxes of carbon and nitrogen, and (6) rates of greenhouse gas emissions across cropping systems and landscape positions.

Our project will also be used extensively for educational purposes. The experimental site, plus a demonstration site proximal to the Iowa State University BioCentury Research Farm, are being used to educate students, producers, individuals from the agribusiness and bioenergy industries, and the general public on the implementation, benefits, and costs of diverse, site appropriate biomass cropping systems. To date, two dozen undergraduate and graduate students have received training on the project.

The output of this project will be a robust platform for policymakers, investors, the agribusiness industry, farmers, and society at large to make informed decisions about potential cropping systems to include in a sustainable bioenergy feedstock portfolio.

Fig. 3 - Experimental plots testing a portfolio approach to bioenergy feedstock production at the Iowa State University Uthe Farm, located in central Iowa
(Photo credit: Tom Schultz).