Climate implications of biomass appropriation: Integrating bioenergy and animal feeding systems.

摘要

Through land use and biomass utilization, humans are dominant forces in the planetary biosphere and carbon and nitrogen cycles. Economic subsidies and policy mandates for producing biomass-sourced fuels and electricity could increase further the human appropriation of planetary net primary productivity. After reviewing the magnitude of organic byproducts available as feedstock, and presenting a model of the climate impact of organic waste management, this dissertation focuses on the climate impact of the main biomass consumers in the United States: livestock, including beef and dairy cattle, chickens (for meat and eggs), pigs and turkeys. Existing estimates of feed consumption by livestock are synthesized, showing that beef cattle in particular are large consumers of cellulosic biomass in the form of hay and grazed roughage. I then determine the extent to which harvesting energy from animal manure can reduce and offset the greenhouse gas (GHG) emissions from producing animal products. Finally, a life cycle assessment (LCA) of an integrated animal product and bioenergy facility is presented. Biomass flows and global warming potential (GWP) are modeled for two systems: one where the animal production and bioenergy facilities are distinct and one where the facilities are integrated. The animal production system includes a mix of animals. Such a system may be able to more efficiently utilize byproducts from each system, but increasing the concentration of animals and manure nutrients may make such a system difficult to implement.