Orimulsion® is a natural bitumen in water emulsion (70% bitumen, 30% water), that is stabilized by a surfactant (less than 0.2%). Orimulsion® is a relatively new fuel that is currently used in several electric-generating stations worldwide. Acceptance and use of the fuel are expected to increase in the very near future. An important consideration in using Orimulsion® as a fuel is the environmental risk associated with the unlikely event of a spill during transportation and trans loading.

This paper shows the dispersion characteristics and the possible environmental impacts of Orimulsion® when this is eventually spilled at sea based on theoretical considerations, laboratory studies, open-sea spill tests, and analytical and numerical modeling.® The results indicate that in the unlikely event of an Orimulsion® spill, it will pose a very low risk of affectation to the biological species that may be in contact with the product. Because of the emulsified characteristics of the product, the dispersion of the bitumen droplets and the dilution of the surfactant will be relatively fast, reaching very low concentrations in the water column in a matter of hours.

The SIMAP model was used to simulate an instantaneous spill of 22,000 barrels of Orimulsion® in a general place without currents and very low turbulence level to evaluate the development of the bitumen droplets cloud. The purpose is to follow the maximum bitumen concentration in order to be compared with the results of different toxicity tests reported in the literature, which represents the worst case scenario for organisms' impact. The results show that all the toxicity values remain relatively far above the maximum bitumen concentration curve. Therefore, if for the worst case scenario the possible environmental impacts of a 22,000-barrel Orimulsion® spills are very low, for normal sea conditions and a smaller spill size, it is expected that the maximum concentration curve will separate even more from the LC50 values, which imply a much lower impact on the marine organisms.

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