摘要: |
The overall objective of this research is to compare canola and soybean as biodiesel feedstocks in terms of net carbon dioxide (CO₂) emission savings with respect to petroleum diesel. Methodology: Contrasting rotations of soybean and canola will be compared in terms of soil carbon sequestration. Measurements will include inputs such as those due to plant and mycorrhizal fungal production, and outputs including soil respiration. The project will also measure processes associated with carbon sequestration including soil aggregation and glomalin production. Rationale: Life cycle analyses have shown that using biodiesel in place of petroleum diesel reduces net CO₂ emissions by approximately 78%. This is because CO₂ from the combustion of biodiesel from plant sources (vegetable oil) is recycled back into vegetation by photosynthesis, and because 3.2 times less fossil fuel is used in the production of biodiesel than in the production of petroleum diesel of equivalent energy content. Therefore, replacing even a small fraction of petroleum diesel with biodiesel can have a significant effect on net CO₂ emissions. However, it is very probable that the choice of crops to produce biodiesel feedstock will have large but as yet unknown effects on net CO₂ emissions because of large differences in their ability to sequester carbon in the soil. In the U.S. the most important biodiesel feedstock crop is currently soybean. In Canada and Europe the most important crop is canola. Canola has vast potential in many parts of the U.S., including much of the NE Sun Grant region, because of its much greater per acre oil yield compared to soybean. Because soybean forms a symbiotic relationship with mycorrhizal fungi that live at the interface of between the root and the soil, it is hypothesized that it will sequester significantly more soil carbon than canola, which is not mycorrhizal. Therefore, it ishypothesize that soybean will result in significantly lower net CO₂ emissions than canola when used to produce biodiesel. No other studies have accounted for soil carbon sequestration in assessing life cycle CO₂ emission reductions with biodiesel, and a direct comparison of competing biodiesel feedstock crops has not been made with respect to net carbon emissions. This research is relevant to both Feedstock Development and Systems Integration Enabling Activities for the BioFuels Strategic Area. |