​Starbucks will eliminate plastic straws from all of its locations within two years, citing the environmental threat to oceans.

The coffee chain becomes the largest food and beverage company to do so as calls to cut waste globally grow louder . While plastic straws account for a small percentage of the waste that ends up in oceans, they've become a flashpoint.

A week after its hometown of Seattle banned plastic drinking straws and utensils, Starbucks said Monday that by 2020, it will be using straws made from biodegradable materials like paper and specially designed lids. The company already offers alternative straws in Seattle.

Other cities, like Fort Myers Beach in Florida, have banned plastic straws. Similar proposals are being considered in places like New York and San Francisco. The push to ban plastic straws gained traction after a viral video in 2015 showed rescuers removing a plastic straw from a sea turtle's nose in graphic detail.

Starbucks has a long history of wrestling with issues of sustainability. One significant — and so far unfulfilled — goal was announced in 2008, when the company said it was aiming to make 100 per cent of its cups recyclable or reusable by 2015.

The issue of waste more broadly is coming up in company boardrooms.

In February, Dunkin' Donuts said it would eliminate polystyrene foam cups from its stores by 2020.

McDonald's shareholders voted down a proposal requesting a report on plastic straws in May. But the burger chain recently said it would switch to paper straws in the United Kingdom and Ireland by next year, and test alternatives to plastic straws in some U.S. locations.

McDonald's also said this year that it would use only recycled or other environmentally friendly materials for its soda cups, Happy Meal boxes and other packaging by 2025.

One reason big chains say it will take time to change may be the difficulty in securing adequate supplies. Imperial Dade, a foodservice and janitorial supplies distributor based in New Jersey, says it's seen a huge spike in demand for alternative straws in recent months.

"Our biggest challenge is trying to locate alternative sources so we can satisfy the demand," said Laura Craven, the company's director of marketing.

While plastic drinking straws have become one of the more high-profile environmental issues, they make up only about 4 percent of the plastic trash by number of pieces, and far less by weight. Straws add up to about 2,000 tons of the nearly 9 million tons of plastic waste that ends up in waters around the globe each year.

The advocacy group 5 Gyres notes that the top five biggest sources of single-use plastic are plastic bags, water bottles, to-go containers, to-go cups and straws.

The strawless lids will begin to appear in Seattle and Vancouver Starbucks this fall, with phased rollouts within the U.S. and Canada next year. A global rollout of the strawless lids will follow, beginning in Europe where they will be used in some stores in France and the Netherlands, as well as in the United Kingdom.