Biodiesel assessment results

As animal fats are a potential feedstock for biodiesel production, Cummins et al. (142) assessed the danger of a human contracting CJD as a result of the use of tallow as a fuel in diesel engines. They concluded that the risk was several orders of magnitude less than the rate of spontaneous appearance of CJD. Thus, scientific analysis indicates that processed (i.e., rendered) animal fat is not an agent of transmission of BSE. Nonetheless, especially in the United Kingdom, the public remains skeptical. This has in some cases led to less use of animal fats in feed applications. Especially in the United Kingdom, the BSE epidemic has reduced the amount of domestically available tallow (because of condemnation) and increased the use of other lipids in place of animal fats. 

When starting a Life Cycle Assessment the first task is the definition of goal and scope. As already mentioned the setting of system boundaries for products based on renewable resources is not straightforward. In order to exemplify die influence of the question what shall be included on the result of the assessment three different scenarios will be compared for the life cycle of biodiesel from tallow and used vegetable oil (see Figure 1). 

The comparison of the two different impact assessment methods is made on the basis of Scenario I, the production of biodiesel from waste cooking oil without the consideration of substitution processes. Since SPI and CML results cannot be directly compared the main focus of investigation is to discuss if both methods point to the same environmental problems arising over the life cycle and identifying the process steps contributing most prominently to the ecological impact. 

Combustion and emission characteristic tests on soybean oil biodiesel have been performed to assess the health effects associated with soybean-based biodiesel emissions. A program at the US Environmental Protection Agency (EPA) showed recently that particulate mass (PM) emissions were 30% lower with BlOO combustion, compared to BO (pure petroleum-derived diesel). Moreover, the latest results were also richer in CO, while being slightly lower in NO and organic acids than BlOO (Mutlu et al., 2015). 

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