How to clean up oil spills – 14 unique methods

What is an oil spill?

An oil spill is a form of marine pollution that occurs when any type of oil spills into an open body of water. The oil floats on the water surface as a discrete mass. As it contains many toxic compounds, an oil spill can harm the biotic and abiotic components of the environment where it takes place.

14 methods used to clean up oil spill

Over the years, there have been several massive and many minor spills in the ocean. As a result, we have come up with some very unique ways of cleaning up oil spills.

Based on the spilled liquid’s type and quantity, environment, and weather conditions, we can choose from a variety of cleanup methods.

It goes without saying that whatever method we choose must be fast, effective, and affordable for a quick return of the site to its initial state.

We can choose from the following methods:

1. Oil-absorbent pads
2. Sawdust
3. Hay
4. Oil Spill Dispersant
5. Skimmer
6. Oil boom
7. Oil-absorbent powder and granules
8. Bioremediation
9. Vacuum pumps
10. Manual removal
11. Mechanical removal
12. High-pressure hot water washing
13. Gelatin treatment
14. In-situ burning

Let us take a brief look and understand each of these methods.

Oil-absorbent pads

Oil-absorbent pads float on the water and absorb oil like a sponge. If they become saturated, we replace them with fresh ones until all of the oil is absorbed.

Most oil-absorbent pads are made of polypropylene. A unique property of this material is that it is hydrophobic as well as oleophilic. In other words, polypropylene attracts oil and repels water. This makes it perfect for use as an oil absorbent.

Moreover, the material also resists acids, bases, and organic solvents. This enables its use as an oil-absorbent without further crosslinking or modification. It can also cover a much larger surface area compared to other methods.

Sawdust

Sawdust is another effective, non-toxic cleaning agent when it comes to oil spills. It is the preferred choice to clean up small spills.

All you do is spread a thin layer of sawdust over the oil and mix it thoroughly with a stiff broom. The sawdust immediately starts soaking the oil and turns into a slick mass. We then sweep, pick it up and dispose of it.

We can use sawdust for oil spills on land as well as water.

Sawdust is one of the agents during bunkering on vessels as it is a quick and effective method to contain a spill.

Hay

Hay is another way to clean up spilled oil. It works like sawdust. You drop it evenly over spilled oil and simulate waves by moving the water around to aid absorption.

Professionals recommend leaving the hay at least for 6-8 hours for effective absorption.

Hay is a low-tech clean-up solution that we can apply anywhere. It works on water as well as land. But caution is important when using it over large masses of water as hay can spread with time. This may make it difficult to recover and become a pollutant itself in the process.

Oil Spill Dispersant

Chemical dispersants contain a mixture of emulsifiers and solvents to break the spilled oil into fine droplets. The droplets are less than 100 microns in size which makes them smaller than the period at the end of this sentence.

An oil dispersant does not decrease the amount of spilled oil. Instead, it allows the oil to seep into the water and prevent it from reaching the shorelines or the marine animals at the sea surface.

But now, the oil comes into contact with underwater aquatic life. This can also lead to severe consequences. Moreover, dispersants reduce the efficiency of skimming the oil from the water’s surface.

An advantage of dispersed oil is that it undergoes microbial decomposition better. This can have net positive consequences depending on the situation.

Skimmer

Skimmers are mechanical devices that separate oil from the surface of the water.

Oil floats on water by virtue of the density difference between the two. We can use skimmers to submerge just under the surface of the water. When the water enters the skimmer, it carries the oil on its surface into the device where the two are separated. Skimmers can efficiently remove the oil from the spill

Skimmers come in various shapes and sizes. They can either be self-propelled, shore-operated, or vessel-operated. They can work in deep as well as shallow water.

They are most suitable for calm water. Rough seas lead to the entry of a greater amount of water into the skimmer.

Oil boom

Oil booms are floating devices that contain the spill of oil by maintaining a physical boundary. They are deployed along the borders of a spill area. A thicker surface of the oil is collected inside the boom. This prevents the oil from reaching the shoreline or spreading over a large area.

Clean-up efforts also become much more effective because of booms. A thicker layer of oil within a small area is far easier to clean than a thin layer that spreads over a vast area.

Booms are often the first oil control devices to be deployed and the last to be picked up. In addition to the pipe-like structure seen on top of the surface (float), oil booms have an underwater looser structure (skirt) that has a height between 45 and 120 cm. The skirt prevents the escape of oil from under the boom.

It works best in calm weather but there are also rugged, heavy-weather booms for choppy weather.

Oil-absorbent powder and granules

Oil-absorbent powder and granules are special materials capable of soaking high amounts of oil at a quick rate. They are designed to absorb oil-based fluids and repel water-based fluids.

They are also eco-friendly, non-toxic, and easier to dispose of than other agents. They are suitable for spills on land as well as water. Typically, the powder finds use in traffic areas where there isn’t enough time to leave the agent in the sea for too long.

Bioremediation

Bioremediation is the use of living organisms that feed on oil to clean up oil spills. These may be of three types:

• Microbial bioremediation (Use of aerobic and anaerobic microorganisms)
• Phytoremediation (Use of plants and soil microbes)
• Mycoremediation (Use of fungi)

As we have read before, bioremediation is more effective when combined with oil dispersants. The small droplets have a greater surface area resulting in a quicker clean-up. Microbes can feed on oil droplets from more directions.

Vacuum systems

Vacuum systems can suck the oil from the water’s surface and collect it in a tank. They are typically used in combination with an oil skimmer. They come in various sizes ranging from a few hundred liters to 3000-liter tanks and more.

A high-pressure water jet with its dedicated tank may expedite the operation by pushing the oil layer towards the vacuum system’s inlet.

Manual removal

Manual removal refers to the removal of oil by humans using hand tools such as rakes, shovels, pans, brooms, and so on. This is especially useful in oiled shorelines with limited access.

When the above methods or heavy machinery cannot reach oil-polluted areas, manual removal is the only method available.

The cleanup crew collects the oil in buckets and transfers it to larger tanks before it goes for disposal.

Despite its limited use cases, manual removal is very common and highly effective for beach cleanups.

Mechanical removal

Mechanical removal is a much faster version of the manual removal process where we use heavy machinery to clean up the oil. We may use frontloaders and backhoes to scoop up oil in greater quantities and collect it for further processing and disposal.

High-pressure hot water washing

High-pressure hot water washing works well for rocky or gravelly shores where the oil traces are still present.

A high-pressure jet of hot water can clean the rocks of the remainder oil very efficiently. We may use fresh or seawater for this purpose.

Such cleaning, however, can have a detrimental effect on the shore’s health. While the shore is much cleaner, such a wash can impact the shore’s future ability to support vegetation and microfauna. It may take many years before the shore is completely restored to its initial state.

The effect is much worse on gravelly shores compared to rocky ones. A hot water wash directly kills the shore organisms as the oil seeps through the gravel into the soil and sediments below.

Gelatin treatment

Gelatin treatment is the use of gelatinous material to collect spilled oil from the water surface. When the material in its ungelled form is dropped onto oil spills, it gels and absorbs/entraps the oil in the process.

Once the process is complete, we need only to pick up the gelled material from the water surface. It is much easier to pick up this material compared to oil. We may use skimmers or nets.

Moreover, the gelled material can be easily recovered by heating. When heated, the gelled material separates from the oil and we can reuse it.

This method works well but requires skill. The gelatin-to-oil ratio is typically 3:1. We need thrice as much gelatin as the spilled quantity. This may not be possible in every case.

In-situ burning

In-situ burning is the practice of controlled burning of spilled oil at the spill site. The oil needs to be contained during the burning process. This is an effective method that can remove almost all of the spilled oil but there are certain downsides.

First is that the air pollution resulting from burning large amounts of oil can have a detrimental impact at the local as well as global level.

Fire and toxic smoke can also affect human health and hence, this method is more suitable for spills that are far away from the shoreline.

Then there is the risk of affecting aquatic life as the residues reach the ocean floor. Even those residues that stay afloat assume a toffee-like consistency and can be difficult to recover.

The oil layer needs to be at least 2-3 mm thick for burning. As the burning progresses and the layer thickness comes down, the fire may extinguish due to the cooling effect of the wind, seawater, and waves.

Types of responses to an oil spill

Let’s do a quick recap. We have listed the different oil spill cleanup methods in the above section.

For a clearer understanding, we can categorize the above 14 methods into 4 distinct groups. They represent the types of responses to an oil spill. These are:

Containment

1. Oil booms

Recovery

1. Oil absorbent pads
2. Sawdust
3. Hay
4. Oil skimmer
5. Oil-absorbent powder and granules
6. Vacuum pump
7. Manual removal
8. Mechanical removal
9. Gelatin treatment

Dispersion

1. Oil spill dispersant
2. High-pressure hot water washing

Consumption

1. Bioremediation
2. In situ-burning

In most cases, multiple types of responses work together to combat an oil spill. Besides the above 14 methods, we have special sponges, magnetic soaps, and autonomous robots in development. These are the latest additions to oil spill cleanup methods.

Conclusion

Oil spills are a serious concern as they can have devastating consequences on the environment. Cleaning up an oil spill is a hard and tedious process. It may take months or years for complete restoration. The Deepwater Horizon oil spill is still detectable after 12 years.

When a spill occurs near the shore, it can have an impact on the health and livelihood of those who depend on the sea or tourism.

Moreover, most of the oil recovered through absorption devices cannot be salvaged and is either sent to landfills or incinerated. Such measures increase other types of pollution.

When it comes to oil spills, prevention is far better than cure. All seafarers need to be extra-vigilant about the risks involved in events such as bunkering, grounding, collision, and cargo loading and discharging.

Human error due to carelessness, ignorance, mistakes as well as machinery failure can prove very expensive if it leads even to a small spill.