Sheehan, John Joseph2014-04-222014-04-222014-03https://hdl.handle.net/11299/163024University of Minnesota Ph.D. dissertation. March 2014. Major: Natural Resources Science and Management. Advisor: Dr. Stephen Polasky. 1 computer file (PDF0; x, 155 pages, appendix p. 147-155.The idea that biofuels can be sustainable has long been controversial. This research considers three land-related aspects of biofuels sustainability:1. The effect of local farm management practices on the sustainability of land used to produce corn grain as a biorefinery feedstock. 2. The relative sustainability of land used for producing corn and sugarcane as a function of latitude. 3. The land use implications for biofuels of global pasture-based livestock production systems. Local corn farm management choices can make the difference between net negative and net positive carbon footprints for grain delivered to biorefineries. Carbon footprints reported here are based on full life cycle assessments of each farm, including modeled soil emissions of greenhouse gases. For a cohort of farmers surveyed in southwest Minnesota, avoiding excess fertilizer use, adopting no till practices and replacing commercial fertilizer with animal manure leads to negative carbon footprints of up to -117 gCO2eq per ha. Globally, the choice of land managed for corn or sugarcane versus land maintained to support natural ecosystems is highly dependent on latitude. On average sugarcane produces three times more energy per unit area than does maize. Latitudes closer to the equator have higher net primary productivity (NPP), so there is a greater trade-off between biofuel production and ecosystem productivity in the equatorial zones. Sugarcane is still twice as productive on average compared to maize in the amount of biofuel energy produced per unit of NPP. Global pasture systems could reduce their land footprint by several-fold simply by closing the gap between poor performing and high performing pasture systems across climatically-similar parts of the world. Because pasture's global land footprint is so large, closing the performance gap could make vast amounts of land available for biomass feedstocks, with no new land clearing.en-USBiofuelsLand useLife cycle assessmentSustainable agricultureSustainable energyThesis or Dissertation