From the data obtained from free fatty acid determination, thermal stress of the fuel had a considerable effect. Although flow was not significantly correlated with increased free fatty acids initially, the clear trend that free fatty acids had with time could be modeled.
The magnitude of the results are seen in comparison to the free fatty acid value of stored biodiesel. In future studies, opacity and color may also serve as indicators of flow restriction and degradation.
Free fatty acids released by chemical reactions in biodiesel fuel should be an accurate determinant of fuel degradation.