Health and Safety Aspects of In-situ Burning of Oil

[Pathfinder]

Health and Safety Aspects of In-situ Burning of Oil
Nir Barnea
National Oceanic and Atmospheric Administration
Seattle, WA 98115 USA​

BACKGROUND​

In-situ burning is the combustion of a spill product at the site of the spill (in situ is Latin
for ?in place?.) In-situ burning of oil may offer a logistically simple, rapid, inexpensive,
and relatively safe means for reducing the net environmental impact of an oil spill.
Because a large portion of the oil is converted to gaseous combustion products, the need
for collection, storage, transport, and disposal of recovered material can be substantially
reduced.​

Required Conditions​

To burn oil on water, four major conditions must be met:​

1. The oil layer has to be thick enough to support combustion. Oil layers
thinner than 1 to 2 mm lose too much heat to the water and cannot support
combustion.​

2. The ignition devices used must be hot enough and last long enough to
ignite the oil.​

3. The water-in-oil emulsion may not contain more than 30 to 50 percent
water to ignite and support combustion.​

4. To use currently available fire resistant booms, environmental conditions
must be favorable: wind speed should be below 20 knots, and wave height
should be below three feet.​

Burning Technique​

An in-situ burning technique likely to be used would employ towing boats and fireresistant
booms to contain the spilled oil and keep it from spreading. The boom, attached
to the boats by towing lines, would be pulled by the boats to form a U shape. The open
end of the U is maneuvered through the oil slick, and a "boomful" of oil is collected. The
boom is towed away from the main slick and the oil is ignited. During the burning, the
boom is pulled so that it slowly advances ahead of the current to ensure that the oil is
concentrated at the back end of the boom and maintains maximum thickness. After the oil
is burned, the process may be repeated for as long as in-situ burning is feasible.​

Burning Efficiency​

In-situ burning has been studied under controlled conditions in laboratories and in field
tests, and recently under realistic conditions in an experiment off the coast of
Newfoundland, Canada. This experience indicated that in-situ burning can be an effective
oil-removing technique, removing 50 to 99 percent of the oil collected in the boom. In
addition, a field "real" burn conducted in the first days of the Exxon Valdez spill in Prince
William Sound, Alaska, resulted in the burning of 15,000 to 30,000 gallons of Prudhoe
Bay crude oil at an estimated efficiency of 98 percent or better (Allen 1990).
2​

Plume Behavior​

The heat generated by the burning oil in the boom (1800 ?F were measured at the top of
the boom at the Newfoundland burn) will cause the smoke to rise several hundred to
several thousand feet, and at the same time be carried away by the prevailing winds. In
areas having well-developed sea-breeze systems, plume fumigation and recycling may
draw the smoke toward the surface. It is expected that the plume will be high enough to
stay out of the sea-breeze/land-breeze circulation cell. The smoke plume at the in-situ
burning conducted off Newfoundland and at marsh and brush burns leveled off at several
hundred feet, and then lofted slowly over distance. The upper boundary of the plume
often extends to an altitude of several thousand feet. The main plume may also split into
two or more smaller plumes, each heading in a somewhat different direction.​

HUMAN HEALTH CONSIDERATIONS​

The possible health hazards of in-situ burning to nearby response personnel conducting
the burn will be different from those for the general public at a substantial distance away.
Response personnel: Response personnel working close to the burn may be exposed to
levels of gases and particulates that would require them to use personal protective
equipment. They should receive the training required to conduct the operation safely.​

Monitoring of the responders' work environment should be conducted as needed.
Occupational standards such as OSHA's Permissible Exposure Limits (PEL) are
applicable to this group of typically healthy adults.​

General public: Based on data from the Newfoundland Offshore Burn Experiment
(NOBE) (Ferek 1994; Fingas et al. 1994; Bowes 1994) and previous burns (Fingas et al.
1993; Booher 1992; Evans et al. 1992), particulate concentrations in the smoke plume
remain the only agent of concern past a mile or two downwind, the gases created in the
burn having dissipated to levels close to background. Public exposure to smoke
particulate from the burn is not expected to occur unless the smoke plume goes down to
ground level. Since the general public may include sensitive individuals such as the very
young and very old, pregnant women and people with pulmonary or cardiovascular
diseases, this population's tolerance to particulates may be significantly lower than that of
the responders. Protecting the general public may be achieved by minimizing exposure
and conducting the burn only when conditions are favorable and exposure to particulates
from the burn is below the level of concern. There is little data concerning the effect of
particulates from in-situ burning of oil on humans. Based on chemical analysis of soot
particulates and their physical behavior, the hazard is expected to be similar to that of
better known particulates emissions now regulated by the National Ambient Air Quality
Standard (NAAQS).​

Determining the level of concern for exposure to particulates is not simple. The existing
NAAQS of 50 mg/m3 annual mean and 150 mg/m3 averaged over 24 hours is designed for
continuous sources such as industry and motor vehicle emissions. In-situ burning is likely
to occur over a short period of time: hours, perhaps a day or two. Is the existing PM-10
standard well suited for in-situ burning? This issue definitely warrants further
consideration./.../​

Full text (8 pages) at:

http://response.restoration.noaa.gov/book_shelf/655_health.pdf