As the demand for electricity grows, power generators are looking for alternative fuels and stable prices. Among the alternatives being considered are a group of multi-component fuels referred to as emulsified fuels. Orimulsion is an emulsified fuel composed of roughly 70 percent bitumen (a heavy tar-like mixture of hydrocarbons with 10 to more than 1,000 carbon atoms that occurs naturally or is obtained as highly viscous residues after refining of crude oils to remove most lighter-molecular-weight components), 30 percent fresh water, and less than 0.2 percent of two additives (a surfactant and a stabilizer). While focusing on Orimulsion, this report describes the nature of emulsified fuels, lists overarching knowledge gaps, discusses potential environmental effects, and outlines the effectiveness of spill response strategies.

• Additional studies using a wider variety of particulate types are needed to address uncertainties in how bitumen interacts with suspended sediments, particularly those with high organic content. Furthermore a validated model predicting spill behavior should be completed and model output should be verified for site-specific application.
• After examining the available literature, the committee concluded that adequate literature was available only for Orimulsion. Thus, this report deals almost exclusively with Orimulsion.
• Because the sediments are the ultimate sink for bitumen droplets, studies are needed to evaluate the bioavailability of bitumen associated with sediments and the effects on plants and animals from long-term exposure to bitumen-contaminated sediments.
• Because there have not been any Orimulsion spills, regulators are faced with having to evaluate these studies and technologies without the practical experience that comes from an actual response to a spill.
• Bioassay tests completed to date have not been supported by adequate and complementary chemical analyses to determine the concentration of exposure to PAH or the surfactant. Further studies are needed to better document the role of PAH partitioning in Orimulsion bioassay tests or in comparison tests involving other fuels.
• Comparison of Orimulsion to other fuels (such as No. 6 fuel oil) would necessitate that similar studies be performed on the fuels of interest.
• During the transport and storage of fuels including Orimulsion, there is always the risk of accidental spills.
• Federal and state agencies should consider developing information on the ambient concentration of surfactants and their degradation products.
• For spills in fresh and brackish water, most response options are not applicable because very little of the spill is expected to float initially or refloat over time. Cleanup will likely consist of removal of bitumen droplets that have accumulated on the bottom in low-flow areas by dredge or vacuum systems.
• Further research is needed to quantify the competing processes of coalescence and dispersion for different spill volumes, release rates, and turbulent energy.
• In the absence of actual incidents, models must be used to predict the behavior of Orimulsion spills. At present, current models have not been validated, yet spill response planners rely on these models to develop response strategies.
• Many of the proposed methods should be further refined to improve their effectiveness, and responders should become familiar with the effective use of these methods prior to a spill emergency.
• Most of the studies conducted to date to evaluate environmental effects from possible spills have focused on water column exposures of marine fish and invertebrates.
• One of the most significant data gaps in understanding the behavior and fate of spilled Orimulsion is the degree of coalescence of the bitumen droplets that are expected to form early in a salt water spill when the concentration is high. Currently, there are insufficient data to accurately predict the percentage of a spill that will surface or sink due to coalescence.
• Orimulsion has unique properties that make it behave very differently from conventional petroleum products.
• There are no studies of the effect of a spill plume on corals or the direct exposure of the undiluted fuel on vascular plants, and there are only limited studies of the effect on other nonplanktonic primary producers.
• There is insufficient information on the bioavailability to and potential impacts of PAH on benthic animals from long-term exposure to bitumen-contaminated sediments. Additional study is needed to better understand the potential risk faced by these organisms.
• These unique properties make the use of standard spill response techniques less effective in tracking, containment, recovery, and cleanup of Orimulsion spills. BITOR recognized these problems and has spent significant time and resources in conducting studies of the environmental behavior, fate, and effects of Orimulsion spills and in developing specialized techniques to support spill response plans.
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