NET Ecosystem Carbon Exchange of Maize and Shrub Willow for Bioenergy.

Maize, an annual crop, and shrub willow, a perennial woody biomass energy crop, are two contrasting crops used as biofuels feedstock. Among the relevant sustainability criteria, ecosystems carbon dioxide (CO₂) net exchange (NEE) is a fundamental aspect of biofuels systems. The objective of this research is to measure and compare the NEE of maize and shrub willow in the northeastern United States using eddy covariance (EC) systems. We installed one open path and one closed path eddy covariance tower in two 10 ha fields, one for maize and one for shrub willow. These towers report NEE, net radiation, soil heat flux, latent heat flux, soil temperature, soil moisture, wind speed, wind direction and air temperature and moisture, at 30 min intervals. Gaps in the raw NEE data will be filled with empirically derived algorithms relating net radiation, temperature, and soil moisture to NEE. We will report the NEE for the months of March (beginning of the growing season) to October. The NEE curves will be compared to determine whether shrub willow present an annual carbon storage significantly higher than that of maize. The information generated will contribute to a more accurate life cycle assessment of bioenergy crops since the carbon balance of feedstock production is a key component of the systems’ carbon footprint.