McDonalds' Facebook McDonald's is on a mission to make its menu more sustainable. Now the fast-food giant is taking on its own coffee.

McDonald's plans to buy all of its coffee from sustainable sources by 2020, Bloomberg reported on Wednesday.

Currently, 37% of the fast-food chain's coffee comes from certified sustainable sources. To increase that figure, McDonald's is working with Conservation International, a nonprofit that has worked with Starbucks to help the chain reach the milestone of using 99% "ethically sourced" coffee.

The coffee industry is under pressure to adopt more sustainable farming methods, but the definition of sustainable remains pretty broad. International standard setters such as Fairtrade and Rainforest Alliances have created markers for sustainable certification.

We reached out to McDonald's to find out more about how it defines sustainable, but we have yet to hear back.

The coffee change-up is part of a wider effort at McDonald's and in the fast-food industry more broadly toward more natural and ethically sourced ingredients. In the last year, the chain has tested fresh beef patties, promised to cut antibiotics from its chicken supply, and replaced margarine with butter in its breakfast sandwiches.

McDonald's coffee is currently better known for its low cost than its sustainable sourcing. Mike Mozart/flickr

"A lot of people have assumptions about what McDonald's food is," McDonald's corporate chef Jessica Foust told business Insider in July. "The industry in general is challenged because there's a stigma in general about what [quick-service restaurant] food is, and that is very, very unfortunate. Personally, I don't think that helps people eat well."

Customers are increasingly demanding that companies be more transparent when it comes to sourcing and ingredients. Chains such as Papa John's, Panera, and Taco Bell have recently cut artificial ingredients from the menu, and others — including Subway, Chick-fil-A, and Wendy's — have worked to cut antibiotics from their supply chains.

With McDonald's four-year plan to revamp coffee, it doesn't look as though the chain's efforts to escape perceptions of cheap and low-quality food are slowing down.