Specially equipped ships could filter plastic from the ocean and convert it into a fuel that would provide power not only for the conversion, but also to drive the ship, creating a self-sustaining clean-up operation.
As much as 12.7 million tonnes of plastic enter the oceans each year and it is eventually ground into tiny particles that can get into the food chain. Present clear-up efforts use ships that collect and store plastic before returning to port, often thousands of kilometres away, to unload the waste and refuel. This is time-intensive and uses a lot of fossil fuel.
But Michael Timko at Worcester Polytechnic Institute, Massachusetts, and his colleagues believe this plastic can be converted into fuel on a ship while at sea using hydrothermal liquefaction. This involves the material being broken down into constituent polymers at temperatures of up to 550°C and pressures of 27,500 kPa.
They believe enough fuel could be created from plastic to sustain the conversion process, power the ship and even store excess.
Timko says that his team’s modelling suggests that large booms placed in the Great Pacific Garbage Patch (GPGP), an area believed to cover 1.6 million square kilometres where waste naturally collects, could gather enough plastic so that a single ship could convert 11,500 tonnes each year.
Timko adds that data about the density of plastic in the GPGP is scarce. However, at all but the very lowest density estimates a ship could be entirely self-sufficient while harvesting plastic from a boom and even generate enough excess fuel to travel between booms and eventually back to port.
Burning the created fuel would generate carbon emissions, but they would be significantly less than the emissions associated with a traditional ship collecting plastic and ferrying it back to port for recycling.
“This is not a silver bullet,” says Timko. “We think it’s an interesting way to add to [the technological solutions] already out there.”
Source: NewScientistTags: Fossil Fuel, Ocean, Plastic, Port, Ships