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Identifying Lands Suitable for Biofuel Feedstock Crops by Dynamic Modeling of Ecosystem Performance

Overview

Demand for biofuel products is expected to increase as the world seeks alternatives to fossil fuels. Currently, ethanol produced from Midwest corn is the most common biofuel product in the United States. The negative environmental effects caused by corn-based biofuel development include soil erosion, water quality impairment from pesticides and fertilizer, and demand for water for irrigation. The feedbacks of these environmental effects may cause local ecosystem changes. Biofuels produced from cellulosic feedstocks such as grasses, forest woody biomass, and agricultural and municipal wastes have lagged behind corn-based ethanol because the biochemistry of conversion is more complex. As the technical challenges are anticipated/predicted to be met in the near future, demand is expected to increase for cellulosic feedstocks as inputs to the refineries that produce biofuels. Our goal is to identify grasslands and marginal croplands that are suitable for growing cellulosic feedstock crops such as switchgrass (Panicum virgatum) while minimizing impacts on food production.

Our initial study area is the grasslands of the Greater Platte River Basin (GPRB). We identify grasslands suitable for conversion to a switchgrass crop by selecting areas 1) that have consistent grassland productivity that is high or fairly high and 2) that have not had severe ecological disturbance (e.g., wildfire, floods, insects, and overgrazing). Our method, known as “dynamic monitoring of ecosystem performance” (Wylie et al., 2008), is able to separate the influence of year-to-year weather changes (e.g., drought) from disturbance changes (e.g., fire or overgrazing) to identify and map suitable areas. Our analysis uses satellite-derived growing season normalized difference vegetation index (GSN) data, weather data, biophysical and geophysical data, and ecosystem or land cover performance models. We make maps of areas that may be suitable for conversion from grassland to biofuel feedstocks. Results from this study provide information to assist land managers and decision makers make optimal land use decisions for cellulosic biofuel development and sustainability. We have done preliminary work to evaluate the potential conversion of marginal croplands to switchgrass. Future work will extend the study area to the Northern Great Plains.


Figure 1. Location of the Greater Platte River Basin (inside the blue outline) and the land cover types as identified in the National Land Cover Database (NLCD) 2001. Grasslands are shown in light yellow and cultivated crops are shown in brown (Homer et al., 2004).

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