Pure and Applied Chemistry

Introduction: The use of in situ burning as a spill response technique is not new, having been researched and used for a variety of oil spills since the late 1960s. In general, the technique has proved effective for oil spills in ice conditions and has been used successfully to remove oil spills in ice-covered waters resulting from storage tank and ship accidents in Alaska, Canada and Scandinavia.

Although there have been numerous incidents of vessel oil spills that inadvertently caught fire, the intentional ignition of oil slicks on open water has only been seriously considered since the development of fire-resistant oil containment boom beginning in the early 1980s. The development of these booms offered the possibility of conducting controlled burns in open water conditions. In situ burning operations using these booms have been conducted at three spills in the last decade: a major offshore tanker spill, a burning blowout in an inshore environment, and a pipeline spill into a river.

In situ burning of thick, fresh slicks can be initiated very quickly by igniting the oil with devices as simple as an oil-soaked sorbent pad. In situ burning can remove oil from the water surface very efficiently and at very high rates. Removal efficiencies for thick slicks can easily exceed 90%. Removal rates of 2000 m3/hr can be achieved with a fire area of only about 10,000 m2 or a circle of about 100 m in diameter. The use of towed fire containment boom to capture, thicken and isolate a portion of a spill, followed by ignition, is far less complex than the operations involved in mechanical recovery, transfer, storage, treatment and disposal. If the small quantities of residue from an efficient burn require collection, the viscous, taffy-like material can be collected and stored for further treatment and disposal. There is a limited window of opportunity for using in situ burning with the presently available technology. This window is defined by the time it takes the oil slick to emulsify; once water contents of stable emulsions exceed about 25%, most slicks are unignitable. Research is ongoing to overcome this limitation.

Despite the strong incentives for considering in situ burning as a primary countermeasure method, there remains some resistance to the approach. There are two major concerns: first, the fear of causing secondary fires that threaten human life, property and natural resources; and, second, the potential environmental and human-health effects of the by-products of burning, primarily the smoke.

The objective of this chapter is to review the science, technology, operational capabilities and limitations and ecological consequences of in situ burning as a countermeasure for oil spills on water. The main focus of this section is on marine oil spills in open water conditions. The use of in situ burning for spills in ice conditions is dealt with in another chapter. Much of the content of this chapter is updated from an in-depth review of in situ burning produced for the Marine Spill Response Corporation (MSRC) in 1994 (ref. 1). Interested readers are encouraged to refer to the original report for fully-referenced details of the summary presented here. The MSRC report is available from the American Petroleum Institute in Washington, DC.