LONDON (AP) — A bubble barrier that prevents plastic waste from reaching the ocean is one of 15 initiatives named as finalists for the year’s Earthshot Prize, a global competition aimed at finding new ways to protect the planet and tackle climate change.

Prince William, the heir to the British throne, unveiled the finalists on Friday. The five winners, who will be announced next month in Boston, will receive 1 million pounds ($1.1 million) to develop their ideas and scale up their projects.

The prince and his charity, the Royal Foundation, launched the prize in 2020 inspired by US President John F Kennedy’s 1962 “Moonshot” speech that challenged Americans to go to the moon by the end of the decade.

William described the finalists as “visionaries” who offer reasons to be optimistic about the planet’s future.

“They are directing their time, energy and talent towards bold solutions with the power to not only solve our planet’s greatest environmental challenges, but to create healthier, more prosperous, and more sustainable communities for generations to come,” he said in a statement.

Among the finalists are The Great Bubble Barrier, a Dutch invention that pumps air through perforated tubes installed in riverbeds and canals to create a curtain of bubbles designed to push plastic up to the surface and into a waste collection system.

This removes plastic from the waterways and prevents it from reaching the ocean, “where it is nearly impossible to capture and remove,” the promoters say.

A startup from Kenya aims to provide cleaner burning stoves to make cooking safer and reduce indoor air pollution. It was the brainwave of Charlot Magayi, who grew up in one of Nairobi’s largest slums and sold charcoal for fuel. When her daughter was severely burnt by a charcoal-burning stove in 2012, she developed a stove that uses a safer fuel made from a combination of charcoal, wood and sugarcane.

The stoves cut costs for users, reduce toxic emissions and lower the risk of burns, Magayi says.

Other projects include Fleather, a project in in India that creates an alternative to leather out of floral waste; Hutan, a conservation project in Malaysia to protects orangutans; and SeaForester, a cutting-edge seaweed farming effort meant to restore the ocean’s forgotten forests.