Never make a promise you don’t intend to keep.

Otherwise you might get almost a million people knocking on your door.

At least, that’s what happened with Starbucks this week — and now the coffee chain has responded.

Take Action: Tweet Starbucks Asking Them to Donate 100% of Unused Food to Charity in the UK

Ten years ago, Starbucks pledged to develop a recyclable coffee cup, and to increase the use of reusable cups to 25% by 2015.

This hasn’t happened yet — and nearly a million people have now signed a petition calling on them to honour it. Almost 15,000 people contacted Starbucks CEO Kevin Johnson directly, demanding that all coffee cups be made 100% recyclable.

In 2008, @Starbucks said it would serve a 100% recyclable paper cup and increase reusables to 25% by 2015. To date, it hasn't done either. It's time for Starbucks to live up to its promises: https://t.co/mihTM1EyBf#EndOceanPlastics#UseLess#Wastepic.twitter.com/5koUprNKqB

— Mike Hudema (@MikeHudema) March 18, 2018

Campaigners even turned up at Starbucks’ annual shareholder meeting in Seattle on Wednesday to protest the delayed response —  bringing with them a giant “cup monster” built from 500 reused coffee cups to stare down the company with bloodshot eyes. The movement is led by a coalition of environmental organisations called Break Free From Plastic.

“We throw away 2.5 billion coffee cups each year in the UK, at great cost to the environment and the taxpayer,” said Sondhya Gupta, a senior campaigner from global advocacy group SumOfUs which is leading the campaign with US-based environmental organisation Stand.earth. “Starbucks cups are pollution, and people have had enough of the broken promises.”

But coffee cup waste is a global problem. In the US, the average American office worker uses about 500 disposable cups every single year — and approximately 60 billion paper cups end up in landfills annually.

However Starbucks has now responded — with another promise.

Do you think #Starbucks should be held responsible for its #StarbucksTrash? Today is the day our petition will be delivered to the @Starbucks annual shareholder meeting! We’re outside right now with our giant cup monster. Add your name before it’s too late https://t.co/wRvKym9P8fpic.twitter.com/flqmZUZLMq

— Stand.earth (@standearth) March 21, 2018

The company has pledged to invest $10 million over the next three years to support entrepreneurs working on new designs to bring fully recyclable cups to the market.

It’s part of a larger fund with a group of businesses in the sustainable consumer goods industry called the Closed Loop Partners’ Center for the Circular Economy. The project is called the NextGen Cup Challenge, and it faces the difficulties of creating a single cup that must pass every recycling law that exists in different countries.

Read More: This Coffee Chain Is the First in the UK to Charge a ‘Latte Levy’ for Disposable Cups

“No one is satisfied with the incremental industry progress made to date, it’s just not moving fast enough,” said Colleen Chapman, vice president of Starbucks global social impact. “So today, we are declaring a moon shot for sustainability to work together as an industry to bring a fully recyclable and compostable cup to the market, with a three-year ambition.”

This protestor is wearing this suit as she tries to get #Starbucks to create a 100% recyclable cup. #Seattlepic.twitter.com/P1wxZyN5EM

— Alex Rozier (@AlexRozierK5) March 21, 2018

The main problem is the plastic lining in each cup that allows it to stand up to the heat of the coffee: a tightly bonded polyethylene liner that British paper mills don’t currently accept.

Starbucks is experimenting with plant-based replacements, but that might mean that the materials become compostable, but not necessarily recyclable. It’s better, but not perfect. The material in Starbucks’ cups could be reused several times over, but not if they’re composted into dirt, according to the Seattle Times.

In a nutshell: it’s not going to be easy.

Read More: 9 Brilliant Ways the UK Is Cracking Down on Plastic Pollution

“Starbucks today agreed to solve its 4 billion disposable cups per year problem, putting it on the right side of history for forests and climate — we think,”  said Todd Paglia, executive director of Stand.earth. “This is the third such commitment Starbucks has made — and if they follow through, it will change the impact of its cups and the worldwide cup market.”

It comes just weeks after Starbucks became the first coffee chain in the UK to impose a “latte levy” on disposable cups. Customers across 35 branches in London will be charged an additional 5p during the three-month trial, after already offering a 25p discount on any drink if you bring in your own cup.

Global Citizen campaigns on the Global Goals, including Goal No.12 for responsible production and consumption. Take action with us here