The Potential of Biofuels as an Alternative Energy Source for the United States

Instructor: Dr. Benjamin Felzer

This week-long seminar will explore how we might use biofuels to counter our use of fossil fuels.  We will focus on ethanol and biodiesel used for the transportation sector.  Because biofuel crops are harvested and grown within a short period of time, they are a carbon-neutral fuel source.  However, there are significant energy costs in production and conversion that counter some of the benefits of using these fuels.  Also, we need to partition available land between crops for food and feedstock, forests for wood and fiber, and pasture for grazing with the land needed to grow crops for biofuels.  The amount of greenhouse gas (GHG) savings from growing biofuels may be partially offset by changes in land use required to grow these crops.  We will explore these environmental costs and benefits.  We will use a modeling approach with a biogeochemical model to answer some of the following questions:

·        What is the total area and yield of corn and soybean in their present-day locations?

·        What is the total area and productivity of grassland outside of present-day croplands?

·        How do these yields convert to energy?

·        What are the other associated crop production and conversion costs?

·        What percent of energy can come from using all the corn and soybean in the U.S. or from planting switchgrass in all the marginal lands?

·        What will be the net savings in GHG emissions from these efforts?

·        What are the GHG implications from growing switchgrass on marginal lands?

Methods (we will all work together):

1.      Develop TEM parameterization for corn (C4), soybean (C3), and switchgrass (*.dat, *.clm files)

2.      Calibrate ctem4.5 with the new parameters

3.      Run TEM4.5 experimental factorial with corn, soybean, and switchgrass, with and without nitrogen fertilization

4.      Postprocess crop yields of corn, soybean, and switchgrass

5.      Do calculations to determine energy yield, net energy gain, and GHG savings

Lectures and Discussions:

1.      Ecosystem Modeling and TEMflux (Mon.)

2.      Introduction to Climate Change (Tues.)

3.      The Role of Land Use in Global Change (Wed.)

4.      Ozone Impacts on Terrestrial Ecosystems (Thurs.)

References:

Hill, J., E. Nelson, D. Tilman, S. Polasky, and D. Tiffany. 2006. Environmental, economic, and energetic costs and benefits of biodiesel and ethanol biofuels. Proc. Natl. Acad. Sci. 103:11206-11210.

Hoogwijk, M., A. Faaij, R. Broek, G. Berndes, D. Gielen, and W. Turkenburg. 2003. Exploration of the ranges of the global potential of biomass for energy. Biomass and Bioenergy 2003:119-133.

Imhoff, M. L., L. Bounoua, T. Ricketts, C. Loucks, R. Harriss, and W. T. Lawrence. 2004. Global patterns in human consumption of net primary production. Nature 429:870-873.

O'Neill, R. V., and J. R. Kahn. 2000. Homo economus as a keystone species. Bioscience 50:333-337.

Rojstaczer, S., S. M. Sterling, and N. J. Moore. 2001. Human appropriation of photosynthesis products. Science 294:2549-2552.

Shapouri, H., J. A. Duffield, and M. S. Graboski. 1995. Estimating the net energy balance of corn ethanol. Agriculture Economic Report No. 721, U.S. Department of Agriculture, Economic Research Service, Office of Energy, Washington, D.C.

Tilman, D., J. Hill, and C. Lehman. 2006. Carbon-negative biofuels from low-input high-diversity grassland biomass. Science 314:1598-1600.

Vitousek, P. M., P. R. Ehrlich, A. H. Ehrlich, and P. A. Matson. 1986. Human appropriation of the products of photosynthesis. Bioscience 36:368-373.

Vogel, K. P., J. J. Brejda, D. T. Walters, and D. R. Buxton. 2002. Switchgrass biomass production in the midwest USA: harvest and nitrogen management. Agronomy Journal 94:413-420.

Wackernagel, M., N. B. Schulz, D. Deumling, A. C. Linares, M. Jenkins, V. Kapos, C. Monfreda, J. Loh, N. Myers, R. Norgaard, and J. Randers. 2002. Tracking the ecological overshoot of the human economy. Proc. Natl. Acad. Sci. 99:9266-9271.

(I?d suggest reading the three attached references ahead of time, Hill et al. (2006), Imhoff et al. (2004), and Vitousek et al. (1986))

Detailed Schedule:

Monday PM:

·        Ecosystem Modeling and TEMflux talk

·        Computer Setup

·        Library Orientation

·        Start literature search for TEM parameters for corn, soybean, switchgrass

Tuesday

·        Introduction to Climate Change talk

·        Continue developing TEM parameters

Wedenesday

·        The Role of Land Use in Global Change talk

·        Calibrate TEM with new parameters to develop new *.dat and *.clm files

·        Submit xtem runs

Thursday

·        Ozone Impacts on Terrestrial Ecosystems talk

·        Process results using excel and energy conversion table

Friday

·        Discuss results

·        Prepare powerpoint presentations

Experiments:

Assumptions:  Assume all cropland is either corn or soybean and entire yield used for biofuels; assume all grassland that is not crops is used for switchgrass; latest version of TEMflux with lulc changes will be called TEM4.5

1.      cropland as corn without fertilization/ switchgrass without fertilization

2.      cropland as corn with fertilization/ switchgrass with fertilization

3.      cropland as soy with fertilization (to simulate N-fixation)

Preparatory setup:

1.      TEM ecd files and source code changes to allow for corn, soybean, switchgrass types (from 12 to 15 types; MAXCMNT = 16 in temconstsflux.hpp)

2.      TEM source code to differentiate perennials from annuals

3.      cohort file to enable switchgrass harvesting only in last decade

4.      hydrological and carbon calibration of TEM4.5 for other biomes