Carbon Budget of Maize and Shrub Willow for Bioenergy

Open Access
Author:
Cangiano, Maria Laura
Graduate Program:
Agricultural and Biological Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
April 03, 2015
Committee Members:
  • Armen Ricardo Kemanian, Thesis Advisor
Keywords:
  • Carbon budget
  • Shrub willow
  • Eddy covariance
  • Maize
  • Bioenergy
Abstract:
In a world economy currently built around the availability of fossil fuels as a source of energy, biomass arises as an alternative and renewable source of energy. Biomass has been a source of energy since ancient times, but biomass industry and biomass production systems are relatively new concepts. As novel production systems, their impact on the environment is uncertain. Of particular relevance is the carbon balance of these systems. The goal of this research is to measure and compare the daily and seasonal carbon balance of maize (Zea maiz L.), an annual crop, and shrub willow (Salix spp. and hybrids), a perennial woody biomass energy crop, in the northeastern US using eddy covariance (EC) systems. The speci c objectives are: 1) to measure the net ecosystem carbon dioxide (CO2) exchange (NEE) of maize and shrub willow in two neighboring elds and, 2) to develop generalized NEE curves for maize and shrub willow crops for a growing season. Collectively, this information will allow us to quantify the NEE of these systems for a growing season. Two EC towers were installed in each fieeld, one with an open path (OP) gas analyzer and the other with a closed path (CP) gas analyzer. These towers report NEE, net radiation (Rn), soil heat flux (G) , latent heat flux (LE), sensible heat (H), soil temperature, soil moisture, wind speed, wind direction and air temperature (Tair) and moisture, at 30 min intervals. Gaps in the NEE, H and LE data were fi lled using marginal distribution sampling (MDS) technique developed by Reichstein et al. (2005). An energy balance closure evaluation was also performed and results were reported with and without corrections for energy imbalance (82% closure for shrub willow and a 67% closure for maize). In this study, NEE from March to December for shrub willow and maize are reported. NEE half-hourly and daily curves, and cumulative values were compared to determine whether shrub willow presents an annual carbon storage higher than that of maize. At the end of the growing season and after harvest, maize behaved as a source of CO2 to the atmosphere of 3.2 Mg C ha