Plastics are among the most common waste and there is a large amount of them in the sea. There are already technologies that can turn plastics into oil. If ships collected plastics while sailing, they could turn them into oil and not have to consume fuel from the mainland. Effective methods are being sought around the world to remove plastics from the ocean. This could be the way to do it.

Hydrothermal liquefaction

One method of converting plastic into useful raw materials is pyrolysis. However, there is an even more effective method called hydrothermal liquefaction (HTL). It can convert plastic back into oil with a minimum of residual waste. There are places in the ocean where there is the highest concentration of plastic waste, the most famous being the Great Pacific Garbage Patch. At the Proceedings of the National Academy of Sciences, scientists have found an ideal way to launch an operation that could clean up the area of ​​plastics.

Overview of the process for plastic removal out of the GPGP showing (A) the total system overview, (B) part of the system of collection booms, (C) a single collection boom, and (D) the HTL reactor.

One obstacle, however, is that currently, “[a] ship that must store plastic on board until it returns to port, often thousands of kilometers away, to unload the plastic, refuel, and resupply,” the paper notes.
“Oil yields from HTL are typically> 90 percent even in the absence of catalysts and, unlike pyrolysis, yields of solid by-products – which would need to be stored or burned in a special combustor – are less than 5 percent,” the authors add. HTL requires temperatures of 300-550 ºC (570-1020 ºF) and pressures 250-300 times higher than atmospheric conditions at sea level.

Ships equipped with HTL converter

So far, it is uncertain how many plastics the ships would have to pick up and how much energy it would cost them. The authors of the study anticipate that the ship would be equipped with an HTL converter, which will allow it to operate permanently at sea. Scientists’ calculations require the ship to collect plastics in a place where there is a large concentration of them.

According to some analyzes, efforts to clean the Great Pacific Garbage Patch could cause zooplankton damage. Cleaning up this area may not have such an effect if humanity continues to produce more plastic waste in the same amount as before. It is not yet certain whether this idea will be implemented. However, it is important that further efforts are made to reduce the amount of plastics in the oceans.

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