Taking action on land before taking action at sea
River barriers for plastics drifting out to sea
What are the solutions? They differ depending on whether we are primarily looking at the waste already at sea or that still on land.
Since the vast majority of marine plastic waste comes from land-based activities, preventing it from reaching the oceans appears to be the priority on which experts agree. For plastic waste that has already reached rivers, many organisations (NGOs, start-ups, etc.) recommend blocking it before it reaches the river mouth. There are two competing techniques. The first is mobile and easy to implement. It consists of a sort of barrier of floating tubes. They are sometimes made from recycled plastics or at least polymers, which is not at all paradoxical. Plastics are still ideal materials because they are waterproof and resistant in a river environment (UV, branches, currents, bad weather, etc.). Some polymers such as polypropylene are relatively inexpensive and these barriers can therefore be made more cheaply. They allow floating objects to be caught and carried by the current towards the shore for recovery.
Blue Barriers are based on a simple but efficient technology to stop floating plastic waste from reaching the oceans. |
The other technique is just as effective but requires some adjustments. Developed by a start-up company based in Amsterdam, The Great Bubble Barrier is based on the creation of a curtain of bubbles emitted by a perforated tube placed at the bottom of the watercourse. Air pumped from the surface feeds this tube and generates a screen that blocks the waste. The diagonal placement of the bubble curtain allows the waste to be guided sideways to a collection device. The advantage of this solution over the previous one is that it allows the recovery of waste floating between the surface and the bottom of the waterway.
The Great Bubble Barrier has been proven in the Amsterdam canals to stop waste. It is efficient even for waste below the surface of the water. |
Vertuoso, a French start-up, has taken an interest in rainwater which, during heavy downpours, can carry urban waste bypassing the clogged sewage system. The young company has designed large traps that are placed at the entrance to retentin basins intended to receive and contain the excess rainwater. The traps are equipped with fine mesh, so they are able to retain objects as small as 5 millimetres. The waste is regularly removed from the traps and sorted before being recycled.
Preventing “mermaid tears” from taking to sea
Ports are also under increasing scrutiny. Whether they are commercial or pleasure ports, they are places that are home to various activities that can lead to waste ending up in the water, whether through negligence or by accident. Therefore, more and more ports, especially pleasure craft marinas, are equipping themselves with small robots that look a bit like their swimming pool cleaning or hoover cousins. They are autonomous and their mission is to collect all floating objects. There are many examples of such robots.
Jellyfishbot is a small marine drone capable of collecting floating waste and oil-spills from the water’s surface. It is particularly effective in nooks and crannies and hard-to-reach areas |
Among them is the Jellyfishbot, the jellyfish-shaped robot whose mobility allows it to reach the tightest places where waste generally accumulates, between boats and docks for example. It is equipped with a net that only needs to be emptied regularly and has an autonomy of over 7 hours. A similar principle is displayed in the Geneseas, a competitor's robot, which has a collection basket and, a notable difference, is equipped with batteries that can be recharged using solar energy. |
In Belgium, in the commercial port of Antwerp, the plastics industry - from polymer manufacturers to processors and logistics companies - has set up a programme called Operation Clean Sweep (OCS) to prevent the loss of industrial pellets (otherwise known as mermaid tears) into the environment. Europe's second largest port in terms of tonnage is a pioneer, having committed itself in 2017 to stop the "leakage" of industrial pellets into its waters. To measure the progress made, the port authorities have been weighing up the number of pellets recovered each year for 5 years. This indicator makes it possible to measure the decrease in the loss of mermaid tears in the port. In 60 months, the figure has dropped from over 8 tonnes to 2.5. Although the objective of zero pellet loss has not yet been achieved, the improvement is unequivocal and shows the importance of involving all economic stakeholders and the authorities.
Ocean-bound plastic waste, the waste that would have ended up in the sea if…
While the issue of plastic and other litter remains a concern in Europe, the situation is in no way comparable to that in most developing countries. For example, we now know that most of the waste that ends up in the Mediterranean comes from the Middle East and North Africa.
Many NGOs work in the field to help populations and also seek out solutions to the issue of waste that accumulates mainly in the streets of disadvantaged neighbourhoods. For example, this is the case of The Plaf, an NGO based in the Philippines receiving support from the Alliance To End Plastic Waste* (AEPW): “We do not specifically collect marine waste, or only marginally. Our strategy is to collect waste on land before it has a chance to get into rivers and the ocean. This is what is known as 'ocean-bound plastic waste'. We collect this plastic waste through our network of over 150 collection points. These are voluntary drop-off points where anyone can bring waste in and drop it in our collection containers. The waste does not need to be sorted or washed, as long as it is plastic, we take care of the rest. These collection points are located in schools, universities, villages, buildings, shops, shopping centres, etc.”, explained François Lesage, the founder of the NGO. The collected plastic waste is then sorted by polymer(s) and prepared for recycling.
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The Plaf has its own production centre. Once washed and crushed, the pellets (in most cases HDPE or PP) are passed through an extruder before finding a new life as boards, poles or even packaging. “We have already created 30 direct jobs and we also indirectly support dozens of other people in the informal waste collection network (ragpickers, junkshops), from whom we buy plastic waste. The current recycling capacity of our pilot plant is 2,000 tonnes per year. We hope to raise funds soon to set up a second plant in the Philippines with a capacity of 10,000 tonnes per year”, concluded François Lesage. |
The Plaf, an NGO based in the Philippines, organises the collection and the recycling of plastic waste. This waste is then given a new life as boards and poles. Thanks to this initiative, 30 jobs have already been created. |
With a presence on all continents, the AEPW supports dozens of initiatives of this type. Their actions with an environmental purpose create jobs and help the most destitute people to get out of poverty. In Mozambique, for example, the Basisa Bazaruto association focuses mainly on collecting waste which, carried by sea currents from the country's large cities and even from the island of Madagascar nearly 1,000 km away, accumulates on the idyllic beaches of this nature reserve. The model is much the same as that of The Plaf and since 2020, all the stakeholders have set themselves the goal of collecting some 100 tonnes of waste every year. At the moment, they are collecting 6 tonnes per month.
* The Alliance To End Plastic Waste is a non-governmental organisation based in Singapore, founded and funded by the chemical and polymer materials industries to promote solutions that reduce and prevent plastic waste pollution of the environment, particularly in the oceans.
What solutions for the waste already at sea?
Some imagine large boats equipped with a system capable of collecting plastic from the sea. This is the case of The Ocean Cleanup, an NGO created by a young Dutchman. This association has developed a 600-metre-long U-shaped net towed by two boats. This artificial barrier is capable of collecting floating debris, from the smallest (a few millimetres) to the largest (macro-waste), including ghost nets several dozen metres wide. At the same time, computer modelling makes it possible to identify the areas where waste accumulates due to currents and thus to know where to deploy the net in order to optimise the collection efforts. Ultimately, The Ocean Cleanup aims to clean 90% of the world's gyres by 2040. Finally, it should be remembered that the NGO also has boats capable of tackling the problem further upstream, in rivers.
Other projects are just as ambitious. For example, the Sea Cleaners association plans to launch a giant 56-metre-long sailing catamaran entirely dedicated to collecting waste at sea in 2024. Depending on the size of the areas and the density of the waste, it should be able to collect from 1 to 3 tonnes of waste per hour. The aim is to collect between 5 and 10,000 tonnes per year, mainly in areas of high pollution concentration in Asia, Africa and South America. The waste collected will be sorted manually on board, processed and recycled using a pyrolysis energy conversion unit. This unit is intended to operate 24 hours a day and convert all the waste into energy, in order to partly power the boat.
Towed by one or two boats, these nets of several hundred metres long, are able to collect all floating debris |
The fisheries industry is stepping up to the plate
Since 2019, a European Directive requires fishing gear manufacturers to plan for the end of life of their products, via the implementation of the principle of extended producer responsibility (EPR) which is already in force in other industries. This system, which is currently voluntary, must be implemented by 1 January 2025 at the latest. Some fishing ports are beginning to organise collection efforts by purchasing large containers in which to collect used fishing nets. This obligation is very important because according to NGOs such as Greenpeace, around 600,000 tonnes of fishing gear (nets, wires, ropes, etc.) are lost in the world's seas every year. Fishing gear is above all a working tool that has a cost, it is how the fishermen make their money. When they are lost at sea, it is most often because of a mechanical accident, a handling error or inclement weather.
Several hundred thousand tonnes of nets are lost in the oceans every year. Collecting them before they sink is crucial to saving the oceans and its wildlife. |
But how can this lost equipment be recovered before it sinks? It is no easy task, particularly in rough weather. The solution lies in the personalisation of fishing gear (at least nets and traps) combined with a geolocation system to be used in case of loss. Many fishing companies equip their nets with a transponder, a small battery-powered device capable of emitting a signal. The only problem is that batteries do not last very long and are not environmentally-friendly if they become detached from the gear. To remedy this, Norwegian researchers have turned the problem on its head and managed to develop a new beacon that is placed on the boat. It is no longer the net that sends out the signal but the boat.
Read all the articles below:
Blue Barriers: how to stop plastic waste from reaching the sea
A bubble barrier to contain marine plastic waste
Jellyfishbot, the marine waste collection robot
The Manta: the first ocean-bound waste collection and recycling ship!
