Amid growing calls to ban bottled water because of environmental concerns, Coca-Cola Co. says it is working to make its "plant bottle" completely plant-based.

The Atlanta beverage maker on Thursday announced it has signed multimillion-dollar agreements with three firms that specialize in plant-based alternatives to traditional packaging made from oil and other nonrenewable resources. The companies are Virent of Madison, Wis., Gevo of Englewood, Colo., and Avantium of Amsterdam.

The "plant bottle," which in North America is used for Coke's Dasani brand, is currently made up of 30 percent plant-based materials. The remainder contains the plastic resins used in the company's other brands.

Coke also uses the "plant bottle" in different products such as Diet Coke and Coke Zero in 20 countries around the world. The bottle is 100 percent recyclable, the company said.

The move is important to Coke as some in the environmental community have accused the bottled water industry of being a big contributor to landfill waste. Over the past three years, a number of national parks, universities, airports and municipalities have banned the sale of bottled water in response to growing concerns about landfill waste.

The company also was accused of using its influence to put the brakes on a plan to ban bottled water at Grand Canyon National Park. The group Public Employees for Environmental Responsibility said the ban, which was supposed to go into effect this past January, was stopped after concerns were raised by National Park Foundation leaders about the impact the move would have on Coke, a big sponsor of the organization.

PEER, which represents state, local and national public employees who are committed to environmental protection, has links on its website to documents showing the discussions between park foundation leaders.

Coke leaders have denied pressuring the foundation to reverse course, but said the company was involved in discussions on the matter along with others in the industry.

Coke said it does have packaging that is made 100 percent of plant-based materials. Its Odwalla juices come in plant-based plastic, but the materials used in that packaging work best in refrigerated products, not in the company's carbonated or water lines.