In a mission to clean up trash floating in the ocean, environmentalists this month removed about 40 tonnes of abandoned fishing nets from an area known as the Great Pacific Garbage Patch.

Key points:

• Non-profit group Ocean Voyages Institute removed the rubbish during a 25-day expedition
• GPS trackers were attached to nets so they could be located later and removed
• Some of the rubbish was donated to artists for educational works about ocean pollution

Mariners on a 43-metre cargo sailboat outfitted with a crane voyaged from Hawaii to the heart of the Pacific Ocean, where they retrieved the haul of mostly plastic fishing nets as part of an effort to rid the waters of the hazards, which entangle whales, turtles and fish and damage coral reefs.

During a 25-day expedition, volunteers with the California-based non-profit Ocean Voyages Institute fished out the derelict nets from a ocean gyre location where currents converge, between Hawaii and California, group founder Mary Crowley said.

The group is among a handful of non-profits working to collect plastic trash from the open ocean, an endeavour that can be dangerous, time-consuming and expensive.

"Our success should herald the way for us to do larger clean-ups and to inspire clean-ups all throughout the Pacific Ocean, and throughout the world. It's not something that we need to wait to do," Ms Crowley said.

The cargo ship returned on June 18 to Honolulu, where two tonnes of plastic trash were separated from the haul of fishing nets and donated to local artists to transform it into artwork to educate people about plastic pollution.

The rest of the refuse was turned over to a zero-emissions plant that will incinerate it and turn it into energy, Ms Crowley said.