Plug Power Inc has signed a deal with Amazon.com Inc to supply green liquid hydrogen, sending shares of the hydrogen fuel cell maker up more than 12% in early trading, Reuters reported, citing a statement from the companies.

Green hydrogen is often referred to as the future of energy because it is a flexible, zero-emission fuel that can be used for transportation and power generation.

Amazon said Plug Power will supply 10,950 tons of green hydrogen annually starting in 2025, which will be used to replace gray hydrogen, diesel and other fossil fuels. The companies, however, do not disclose the specifics of the pricing of supplies.

Gray hydrogen is produced from natural gas without carbon sequestration and makes up the majority of the 90 million tons of hydrogen produced in the world each year.

The green hydrogen deal will provide enough annual capacity for 30,000 forklifts or 800 heavy trucks, Amazon said.

Amazon said it is using hydrogen to power more than 15,000 fuel cell forklifts and plans to increase that number to 20,000 units within three years. The company also has an order for 100,000 electric delivery vehicles from Rivian Automotive Inc, in which it is the largest shareholder, according to Refinitiv.

Plug said the deal with Amazon will help the company grow towards its goal of reaching $3 billion in revenue in 2025. The company has issued a warrant to Amazon to buy up to 16 million of its shares at $22.9841 per share for the first 9 million shares.