Nutrient recycling in biofuel production systems: Biomass ash pelleting, ethanol co-product allocation, and a beef-ethanol production system analysis.

摘要

Relative to fossil fuels, biofuels help to close the carbon cycle; however other essential nutrient cycles remain open. When biomass is removed from the agricultural landscape for biofuel production, essential plant nutrients such as nitrogen (N), phosphorus (P), and potassium (K) are also removed and concentrate in biorefinery waste streams and low value co-products. This thesis comprises three analyses related to nutrient cycles in the emerging bioeconomy. In the first, combusted biomass ash was pelleted and evaluated as a potential fertilizer. In the second, an energy co-product credit for corn dry grind ethanol production has been determined by examining the effect of variable inclusion rates of distillers grains (DG) in cattle diets. In the third analysis, the net energy and spatial concentration of nutrients and water consumption have been determined for an integrated beef-ethanol production system that benefits from recovering energy from co-product streams and co-locating complementary unit processes.