How to combat oil spills: Technologies and solutions

Oil spills regularly occur around the world, with the majority resulting from maritime disasters. According to researchers, more than 9 million tons of oil have leaked into the ocean since 1960, 5.87 million tons of which were released after tanker accidents. During the Kerch Strait spill on December 15, 2024, the leak amounted to between 3,000 and 5,000 tons of fuel oil. The accident resulted in an environmental disaster, with the total contaminated area reaching 400 square kilometers and extending to the coast of Crimea. Environmentalists estimate that it may take 10 to 15 years for the region’s ecosystem to recover.

Fuel oil on the shore of Anapa (Photo: earthtouches.me)

Spills most often occur due to corrosion of pipelines, deterioration of vessels, military action, human error, accidents, and ship collisions. It is crucial to stop the spread of oil in the first hours after a spill. Only then can recovery and environmental cleanup begin. Depending on the tools and technologies used, spill cleanup can be divided into several groups.

Mechanical methods

Mechanical cleanup is more effective in the first hours after a spill, when the oil layer remains thick enough to be collected. Mechanical cleanup uses oil containment booms, skimmers, and natural and synthetic sorbents. These help stop the spread of the spill and preserve the oil products until they can be disposed of or reused.

Oil containment booms

Booms are floating structures placed around an oil slick that stop its spread across the water’s surface and reduce shoreline contamination. They help collect the oil in thicker layers and direct it in the desired direction, simplifying its removal.

A pollution slick enclosed by a boom (Photo: larn163.ru)

The boom consists of individual sections connected by watertight locks that prevent oil leakage. Each section includes:

• A freeboard that extends above the water and prevents oil from spilling over;
• A float that holds the structure afloat;
• A submerged skirt that prevents leakage from below;
• An upper load-bearing element — a steel cable that supports the longitudinal load;
• A lower load-bearing element — a steel chain that acts as ballast and allows the boom to adhere firmly to the water surface

Booms form a barrier around the oil slick, preventing oil from spilling over the barrier and spreading underwater. They can be quickly deployed from ships or from the shore. However, their effectiveness depends on the weather: the higher the waves, the less effective the boom is at containing the spill. At wave heights greater than a meter and current speeds exceeding one knot per hour, the booms no longer function properly.

Such structures are made of oil- and environmental-resistant plastic, such as special PVC.

However, if specialized equipment is not available at the time of a spill, booms can be made from any available materials: wood, plastic pipes, inflated fire hoses, car tires, and even empty oil barrels.

Oil skimmers

Skimmers are devices for collecting oil from the water surface. They can be self-propelled, or they can be controlled from shore or vessels. The effectiveness of these devices also depends on sea conditions. Even in moderate waves, skimmers typically collect more water than oil.

There are several types of skimmers, including:

• Weir or weir skimmers use a dam or barrier installed at the interface between oil and water. Oil floating on the surface spills over the dam, is separated from the water, and is sent to a reservoir inside the skimmer. The collected oil is then pumped into a storage tank for processing or disposal.
• Oleophilic (“oil-attracting”) skimmers use belts, discs, or continuous chains of oleophilic materials to remove oil from the water surface. These devices operate on the principle of adhesion: the skimmers are made of materials to which the oil adheres. A belt or tube made of oleophilic material is passed through contaminated water, where it captures the oil. It is then transported to cleaning belts or discs. Continuously rotating, they collect the oil in a reservoir. The removed oil can be disposed of or reused.
• Suction skimmers operate similarly to a vacuum cleaner. Oil, along with a small amount of water, is sucked up through a wide nozzle and pumped into storage tanks. There, the mixture separates, and the oil is pumped into a separate container. Suction skimmers are most effective in calm waters where oil has accumulated near booms or barriers.
• Cyclones create an artificial whirlpool with zones of low and high pressure, which separate the oil film from the water.

Cyclone Skimmer (Photo: ecosvc.ru)

Skimmers are typically used after an oil slick has been contained using booms. They effectively remove oil from the water’s surface, reducing its impact on the environment, and therefore serve as a key element in spill response.

Sorbents

Sorbents are materials that absorb petroleum products. Both natural sorbents (sawdust, moss, sand, lime, peat, diatomaceous earth) and synthetic ones (polypropylene, polyethylene, polyurethane) are used for spill response. Sorbents work either by absorbing oil through their pores or by forming a surface layer that traps oil molecules. The materials are distributed over the contaminated area and saturated with oil, after which they are collected using nets or vacuum systems. Some sorbents can be reused by pressing out the oil using a press or centrifuge. However, they most often have to be disposed of. Sorbents are used for localized spills because they are easy to use and do not require sophisticated equipment.

Controlled burning

In-situ burning is a highly effective method for removing oil from the surface of water bodies, but it carries significant risks and environmental hazards. Therefore, incineration has not become the first line of defense for spills, and in Russia, it is used only after approval from the Ministry of Emergency Situations.

Incineration can eliminate up to 98% of spilled oil, but the toxic substances released during combustion pollute the air and can seriously harm seabirds and animals. Furthermore, there is always a risk that the fire will spread beyond the spill site to surrounding vessels and buildings, so the process must be carefully monitored.

Controlled burning of a small oil slick (Photo: korabel.ru)

The effectiveness of burning depends on the thickness of the oil slick, as a certain oil concentration is required for ignition and sustained combustion. Therefore, burning is most often used on fresh spills with thick slicks, as thin slicks may not support combustion or produce excessive smoke.

Chemical methods

Used in combination with mechanical methods, these prevent oil from reaching the shoreline.

Dispersants

Dispersants, or dispersing agents, are chemicals used to break up oil films into small droplets. When sprayed onto an oil slick, dispersants alter the orientation of the oil molecules, reducing surface tension and breaking the oil into particles less than 0.1 mm in diameter. These droplets then disperse in the water and, over time, are naturally broken down by microorganisms. Dispersants also prevent oil from adhering to hard surfaces, including bird feathers, sand, rocks, and pebbles.

These substances are most often used for film thicknesses of 0.1 to 1 mm, when mechanical cleaning is impossible. They are sprayed from slow-moving ships or low-flying aircraft. This method allows for the rapid treatment of large and hard-to-reach contaminated areas.

Dispersants work best immediately after a spill, before the oil has been exposed to air and water and weathered. Water temperature and salinity, weather, and the type of oil also affect the method’s effectiveness. Heavy crude oils generally do not disperse as well as light and medium grades.

Spraying dispersants from an aircraft (Photo: korabel.ru)

Gelling agents

These substances form a rubber-like structure upon contact with oil. For small spills, chemicals can be sprayed manually; they will react with the oil. For larger spills, the agents are mixed with the oil using a high-pressure water jet. The thickened oil is removed from the sea using nets, suction equipment, or skimmers and is sometimes reused after mixing with fuel.

Gelling agents are used in small to moderate waves. In these conditions, the waves themselves help mix the reagents with the oil, causing it to thicken faster and form clumps that are easier to collect. Large waves generally prevent the use of such agents because the reaction may be uneven, making the oil more difficult to collect.

This technology has several drawbacks that limit its use. Firstly, a very large quantity of the substance is often required, three times the volume of the spill. For oil spills of thousands of tons, storing, transporting, and distributing such a large amount of material is impractical. Secondly, care must be taken to prevent fish, birds, and other animals from entering the thickened oil.

Biological agents

These organisms accelerate the natural breakdown of oil. In nature, bacteria, fungi, yeast, and algae slowly break down petroleum products into simple compounds. This process is also known as biodegradation. The use of biodegradation agents accelerates this process and enhances the activity of microorganisms.

Biological agents are the most environmentally friendly method of spill response, as microorganisms break down oil into non-toxic compounds that do not require disposal. Typically, biodegradation agents are used in the final stages of cleanup, after the bulk of the contamination has already been removed.

Natural environmental restoration

Natural restoration is driven by sunlight, wind, and microbial activity, which break down oil spills over time. This allows nature to mitigate the impact of a disaster without direct human intervention. This approach is feasible in areas where the potential environmental harm from cleanup operations outweighs the benefits.

Natural restoration is most effective in areas with small waves, where oil can degrade over time. Microbial activity plays a key role in oil degradation: natural populations of bacteria and other microorganisms feed on the oil and break it down into simpler compounds. Sunlight and wave action help disperse the oil and accelerate its degradation, while wind can carry droplets inland, where they can be further degraded by land-based microbes.

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