Sea : The Manta: Innovative eco-ship on the hunt for marine debris

The ship's design is based on a ray. A technical consortium of around twenty companies and five research laboratories spent three years working on the concept. The result was a giant catamaran 56.5 meters long and 26 meters wide that moves by using two sails with a total area of 2,500 square meters. Power is supplied by two wind turbines, two hydroelectric generators á 100 kW and almost 500 square meters of photovoltaic solar panels.

One of the Manta's main tasks is to collect marine debris. Thanks to a unique combination of four complementary collection devices, the Manta can collect floating macro debris as small as ten millimeters and as deep as one meter. There is no danger to marine fauna in the process. For one thing, the catamaran will move at a slow speed of two to three knots. For another, the nets are equipped with slip-through holes, and ultrasound is also used to warn the animals.Cranes on the starboard and port sides serve for larger debris such as fishing nets. In addition, two smaller boats - named "Mobula" after the Japanese devil ray - with a capacity of five to ten cubic meters of waste can be used: the smaller one in calm waters, the other also in stronger currents or higher waves.

In the catamaran, waste collected in collection carpets is lifted out of the water by inclined conveyor belts with a suction system, and goes onto conveyor belts where it is manually separated. Metals, glass and aluminum waste are separated out, placed in two lifting containers of 40 tons each and later recycled locally on land. Organic waste ends up back in the sea. Plastic waste passes through a shredder and can be pressed into pellets. However, Frederic Silvert, a specialist in the Manta technology, points out that the material must be dry and - unlike household waste - desalinated and dechlorinated before further processing.

A plant then converts the collected, sorted plastic that can no longer be recycled into electricity. Pyrolysis melts the material conveyed through a screw without a combustion process, creating syngas. The captured syngas enters a combustion chamber, and the resulting steam drives a generator and eventually a turbine that powers all onboard equipment: cockpit and navigation instruments, batteries, propulsion, and collection and sorting equipment. The plan is to achieve energy autonomy of 50 to 55 percent. With this technology, the Manta will have a recycling capacity of 3.5 tons per hour in the future. Annually, this is expected to add up to 5,000 to 10,000 metric tons of plastic to be fished off at those locations that are considered to be the main sources of waste entering the oceans - especially river mouths in Africa and Asia. But the objective is also to be flexible and open to areas that have been affected by natural disasters, Frederic Silvert explains.

Collecting marine debris is not the only task of the Manta, which has been designed with energy efficiency, weight reduction and heat recovery in mind, in order to operate "virtually emission-free" and "largely autonomous" in terms of energy. The overall concept will also include the operation of an international research laboratory and a competence and information center on board the ship that will be open to the public. It is not for nothing that the ship is to have capacity for 34 people: in addition to twelve skippers, at least as many scientists.

At present, the catamaran is still in the planning stage, and according to Yvan Bourgnon, the Manta initiator and founder of the environmental protection organization "The SeaCleaners," only a third of the financing for the total sum of 35 million has been covered. Nevertheless, he sees his project as the beginning of "a new generation of ships" with a different CO2 footprint. He expects the current eco-catamaran to reduce CO2 emissions by 75 percent. The first Southeast Asia voyage is scheduled for 2025.