The Interceptor Barrier

As we all know, the plastic pollution in our oceans has reached catastrophic proportions for the oceans themselves and the creatures that live in it, as well as the damage it does when it’s washed up on our beaches.

It’s a never-ending job to clean the beaches and what is washed up is only a fraction of the problem.

But in Guatemala a project to reduce the amount of plastic reaching the sea is being trialled by Ocean Cleanup, which is a non-profit organization developing and scaling technologies to rid the oceans of plastic.

The Rio Las Vacas, a tributary of the country’s largest river, the Rio Motagua, is close to Guatemala City, which is home to around a million people.

Due to extreme weather events, flash floods in the city bring huge amounts of rubbish through the Rio Las Vacas, which in turn feeds into the Motagua and eventually the sea.

One of Ocean Cleanup’s initiatives is to create a barrier across the country’s largest river, The Rio Motagua, in an attempt to catch as much rubbish as possible before it enters the sea.

Following an unsuccessful trial last year, an improved version is being developed using the data from the first attempt to rectify the faults in the original design. The foundations have been improved and the new design allows water to pass through whist rubbish is collected behind the barrier.

Heavy duty floating booms capture the plastic whilst the water can flow underneath.

The barrier has been moved 500 metres upstream from the original location to help with the pressure the system suffered from on the first attempt. A second barrier downstream catches what the first one doesn’t.

The whole system is monitored and from the data collected, any changes that need to be made to improve the efficiency can be carried out. This could be the tautness of the anchor chains or the height of the steel mesh to minimize leakage.

Collecting the rubbish is only part of the story of course – it has to be removed from the barriers, weighed to determine the quantities and then passed on to waste management organisations. A collaboration with Guatemalan NGO BiosferaGT, which is supported by Coca-Cola, has created a waste sorting centre, set up in a bid to recycle some of the waste. Local people are employed to help with this. If successful the idea is to scale up the scheme to make even better improvements.

Ocean Cleanup have also for a while been capturing plastic from the surface of the oceans, by deploying a large U-shape barrier, powered by two boats that guides the waste into what is known as a retention centre. The U-shape is critical (the original V shape proved largely ineffective) and it is this shape that makes the water inside it circulate the currents to move the plastic into the retention centre.

When in motion, the boats have to work together to maintain speed and direction for optimum collection of waste.

Once the retention system is full, the back of the retention zone is taken aboard, sealed off, detached from the system, and emptied on board the vessel. The retention zone is then put back in place and the cleanup continues. The collected waste is then taken ashore for recycling.

Boat speed is important, and can be varied depending on weather conditions; if storms are predicted, the system can be withdrawn temporarily.

The system is being used in several locations and is being scaled up whenever possible. Lessons are being learnt all the time from these prototypes, and solutions found to any problems along the way.

It seems a shame that we have to resort to projects like these - surely it would be better to dispose of waste more responsibly in the first place, and also to use less plastic wherever possible - but the schemes are unfortunately necessary so it’s good that organisations like Ocean Cleanup exist and have the expertise and imagination to solve problems that we create for ourselves.