The Prince of Wales met all 15 Earthshot 2022 finalists for the first time on Thursday.
Prince William quizzed them on what they need to scale up their projects and promised to connect them with the right organisations.
He joined the finalists as they took part in an inaugural, week-long “fellowship retreat” at Cumberland Lodge, Windsor.
It was organised to help the finalists collaborate with each other and future proof their various initiatives.
He spent around an hour chatting to each group of finalists in their respective categories; protect and restore nature, revive the oceans, clean the air, build a waste-free world and fix the climate.
“I’m going to be writing long letters and making a lot of phone calls,” he said.
It is hoped that the course, which ends on Friday, will allow finalists to meet, learn from and collaborate with each other.
Speakers included Christiana Figueres, former UN climate chief and chair of the Earthshot Prize, and Hindou Oumarou Ibrahim, environmental activist, geographer and member of the Earthshot Prize Council.
William spoke to Min Wang, whose company, Desert Agricultural Transformation, turns desert sand into agricultural land.
She invited William to visit one of her project’s sites in China.
He said: “If I am passing by I will be visiting all of your projects. I have made a note to my team.”
He added: “So by year 10 I will still be visiting Earthshot projects.”
He also spoke to Kaushik Kappagantulu, whose company Kheyti’s mission is to increase climate resilience for smallholding farmers in India.
William praised the initiative, adding: “Kenya and India are two countries that are really stepping up to the mark.”
He then met Charlot Magayi, whose company Mukuru makes clean and reliable cook stoves for low-income households in western Kenya.
Ms Magayi grew up in Mukuru, the third largest slum in Kenya. Her business focuses on providing families with clean stoves that are less likely to expose them to harmful air pollution in their own homes.
William gave her a particularly warm greeting.
“Congratulations,” he said. “The last time I saw you you were surrounded by children. Your story is unbelievable.”
Speaking to the PA news agency afterwards, Ms Magayi said: “I started my business in 2017 because my daughter got burned by a traditional stove.
“I grew up in a slum in Kenya, and that is the reason why my business is called Mukuru.
“So I wanted to create a stove for my community, and then we did, and it just blew up.”
William went into private group sessions with the finalists, where they spoke to him about their hopes and ambitions for the year ahead.
The finalists are on the second last day of a week-long retreat at the lodge, where they have met, learned from and collaborated with each other, and heard from leaders and thinkers who have advised them on how to scale up the projects they are working on.
William is the founder and president of the prize, which honours environmental pioneers.