Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 1
Spills of Emulsified Fuels: Risks and Response Executive Summary As the demand for electricity grows in the United States, 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. One such fuel, is known as Orimulsion® (referred to simply as Orimulsion throughout the report), produced by Bitúmenes Orinoco, S.A. (BITOR), a subsidiary of the Venezuelan national oil company Petroleos de Venezuela, S.A. (PDVSA). Orimulsion is a multi-component fuel composed of roughly bitumen (70 percent), fresh water (30 percent), and two additives (a surfactant and a stabilizer, <0.2 percent). Bitumen is an asphaltic or heavy tar-like mixture of hydrocarbons with from 10 to more than 1,000 carbon atoms that occurs naturally or is obtained as highly viscous residues after refining (distillation) of crude oils to remove most lighter-molecular-weight components. The natural bitumen used in Orimulsion comes from the Orinoco belt in Venezuela, which has one of the largest reserves of petroleum in the world. For information on petroleum formation and the natural processes that affect petroleum the NRC report “Oil in the Sea” (1985) is recommended. The extensive reserves and limited market for bitumen allow BITOR to offer long-term contracts at fixed rates significantly lower than many other fuels. Orinoco bitumen is highly weathered and too viscous to flow; thus, BITOR developed many innovative methods to extract the bitumen and produce a fuel that can be used in power generation. A diluent (kerosene) is added at the wellhead to help move the bitumen from the production fields to the Orimulsion manufacturing facility. The diluent is completely removed, and an emulsion is formed by mixing the bitumen at high energy with a surfactant, a stabilizer and
OCR for page 2
Spills of Emulsified Fuels: Risks and Response fresh water from the Morichal River. The Morichal River is a relatively pristine river with no human or industrial activities nearby. The water is filtered and chlorinated to remove any bacteria. In 1998, BITOR modified the formulation, and the new product is marketed as Orimulsion-400. In 1994, BITOR implemented special precautions in spill prevention and safety measures. These measures include the use of only double-hulled vessels both at sea and in rivers, and requirements for special procedures and equipment on rivers. The vessels are prescreened through vetting procedures with special criteria. During the transport and storage of fuels including Orimulsion, there is always the risk of accidental spills. As with other liquid petroleum products, transport of this fuel requires development of an emergency response plan. However, Orimulsion has unique properties that make it behave very differently from conventional petroleum products. First, the density of the emulsified product is intermediate between fresh water and salt water. Therefore, Orimulsion will float, sink, or suspend in the water column, depending on the water density. Second, the emulsion breaks when diluted sufficiently with water. Therefore, following a spill the components separate into the bitumen droplets (with a coating of surfactant) and the freshwater component that contains the dissolved polynuclear aromatic hydrocarbons (PAH), surfactant, and stabilizer. In this case, the fate and possible effects of each component must be evaluated separately. 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. 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. Therefore, the U.S. Environmental Protection Agency (EPA) and U.S. Coast Guard (USCG) requested the NRC to undertake a fast-track study to assess the validity and usefulness of the current work on a variety of emulsified fuels. However, after examining the available literature, the committee concluded that adequate literature was available only for Orimulsion. Thus, this report deals almost exclusively with Orimulsion. BITOR, the company that manufactures Orimulsion, funded many of the studies on the behavior of emulsified fuels cited in this report. Except where specifically discussed, the committee found the studies described in the available literature to be well executed and documented, and to have followed established laboratory practices. Consequently, the committee found no reason to question the validity of the analyses reported. As noted throughout the remaining chapters, the committee did identify areas in which study
OCR for page 3
Spills of Emulsified Fuels: Risks and Response design and the resulting interpretations should be reexamined and some underlying assumptions reevaluated. UNDERSTANDING THE PROBLEM To describe the potential environmental effects of Orimulsion spills or identify information needed to support spill response planning, it is necessary to understand how the product behaves when released into the environment. The breakdown of the emulsion when diluted with water releases a cloud of bitumen droplets. In fresh water, the surfactants attached to the bitumen droplets retard coalescence of the bitumen; however, an increase in water salinity to about 6 parts per thousand renders the surfactants ineffective. Breakdown of the surfactant permits the bitumen droplets to agglomerate or coalesce (although the conditions of this process are not well understood) and form larger droplets, which increases the likelihood of them floating in salt water. Re-floated bitumen will form sticky tarballs and patties that behave similarly to tarballs from other types of heavy fuel spills. The ultimate fate of the bitumen will depend on the spill location and conditions, but those droplets that do not re-float will ultimately be degraded and deposited on the bottom. The bitumen droplets do not adhere to suspended particulate material in fresh water, because traces of surfactant adhering to the bitumen appear to be effective even after dilution. However, in brackish or full strength seawater, bitumen will likely adhere to suspended particulate material (SPM) that can be transported to the bottom or onto the shoreline. When the emulsion breaks, the water component of Orimulsion that is released contains PAH dissolved from the bitumen droplets as well as the two additives: a water-soluble nonionic surfactant (a mixture of widely used alcohol ethoxylates [AE]) and an emulsion stabilizer (monoethanolamine). The additives are biodegradable and, because of their high water solubilities, are unlikely to bioaccumulate. However, the fate and toxicity of biodegradation products have not been characterized completely. As with spills of any material, site-specific environmental factors to a large degree control the fate and effect of spills of emulsified fuels such as Orimulsion. In an effort to articulate general concerns that vary with the changes in environmental conditions, six different scenarios for Orimulsion spills in open and closed water bodies, at different salinities and with varying degrees of turbulence, were developed by the committee. It is clearly beyond the scope of this study to develop site-specific, quantitative discussions of the fates and effects of spills of emulsified fuels that could occur in the future. Therefore, the committee developed qualitative descriptions of the expected fates of the dispersed bitumen droplets and dissolved constituents as a function of time for a range of environmental settings. These scenarios provide a summary of general conclusions regarding
OCR for page 4
Spills of Emulsified Fuels: Risks and Response spill behavior and a basis for later assessment of the environmental impacts of spills and the efficacy of spill response strategies. OVERARCHING GAPS IN KNOWLEDGE The bitumen used to prepare Orimulsion is highly weathered (degraded). Thus, Orimulsion has very low concentrations of volatile organic components, and total benzene, toluene, ethylbenzene, and xylene (BTEX) concentrations are an order of magnitude lower than those observed in a typical No. 6 fuel oil. More importantly, total PAH (the major source of toxicity in oils) concentrations in Orimulsion are very low and up to one order of magnitude below those typically found in No. 6 fuel oil. The concentration of PAH in the water phase of Orimulsion and the receiving water body after a spill is largely controlled by the rates of absorption and desorption of PAH onto bitumen droplets in the neat fuel or bitumen droplets and suspended particulate matter in the receiving waters. These processes can be described by equilibrium partitioning theory, which predicts that additional PAH should desorb from the bitumen droplets (especially given their high surface-area-to-volume ratios) when the water phase is sufficiently diluted. Studies of Orimulsion using standard techniques for describing equilibrium partitioning theory indicate that the maximum theoretical concentration that could be seen by exposed organisms cannot exceed the effective initial concentration of dissolved PAH in the neat fuel (15-30 parts per billion). Although reasonable, these theoretical studies have to be verified independently using analytical laboratory techniques at a variety of dilution factors, as part of a specifically designed study. Furthermore, comparison of Orimulsion to other fuels (such as No. 6 fuel oil) would necessitate that similar studies be performed on the fuels of interest. Because there are significant limitations in containment and recovery of spilled Orimulsion, past research has been concentrated on spill prevention and on understanding the behavior and effects of Orimulsion spills. 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. 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. To support better site-specific response plans and identify the types of equipment that should be available, improved models have to be developed. Additional studies using a wider variety of particulate types are needed to address
OCR for page 5
Spills of Emulsified Fuels: Risks and Response 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. POTENTIAL ENVIRONMENTAL EFFECTS The composition and behavior of Orimulsion directly influences the environmental effects of the spilled product. For spills in fresh and brackish water, where none of the bitumen will be on the surface, direct impacts on shorelines and animals that use the water surface (birds, mammals) will be greatly reduced (compared to floating oil spills). In salt water, the potential for impacts on these resources will be a function of how much of the bitumen resurfaces. Conversely, compared to floating oils, potential impacts on benthic and water column resources from spills of Orimulsion may be increased. Because the bitumen is so highly weathered and the effective concentration of PAH in the water phase is also low, the amount of toxic PAH biologically available is also low. This suggests that acute impacts from PAH toxicity will be negligible except in settings where the plume dilutes very slowly. However, 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. 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. 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. 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. Thus ingestion or contact with these droplets by benthic organisms represents a viable pathway of exposure. 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. The water fraction of Orimulsion contains two additives. The stabilizer, monoethanolamine (MEA) has low toxicity and poses no apparent risk to aquatic resources. The surfactant mixture, composed of alcohol ethoxylates (AE), is widely used in household and industrial products; thus, potential impacts have to be considered in light of the background concentrations of these chemicals and their intermediary decay products in rivers and streams that receive sewage dis-
OCR for page 6
Spills of Emulsified Fuels: Risks and Response charges. Under most conditions, concentrations are expected to decrease quickly below no-effect levels for the parent compounds. There is uncertainty, however, about the toxicity and degradation rates of intermediate breakdown products. To place the potential impact of the release of these surfactants (whether through a spill of Orimulsion or from other existing sources through the wastewater stream) in context given their widespread use, more information on their background concentrations and behavior in the environment is needed. Federal and state agencies should consider developing information on the ambient concentration of surfactants and their degradation products. EFFECTIVENESS OF SPILL RESPONSE STRATEGIES Because Orimulsion is pre-dispersed, the initial response strategy will be to track the suspended plume and monitor for any surfaced tarballs. The tarry nature of the surfaced bitumen requires specialized skimming, pumping, and handling systems, and such systems have been prototyped and tested under limited conditions. 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. 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.
Representative terms from entire chapter: