Back in 2008 the Seattle-based coffee magnate, Starbucks, proclaimed that all of their coffee shops would offer recycling by 2015. The company’s recycling efforts kicked off at a piecemeal pace, with just a few select stores offering to recycle the company’s trademark white and green cups. Six years later, the company has only managed to expand its recycling program to 39% of its stores.

What keeps a coffee company worth 54 billion dollars from recycling 100% of its coffee cups? The answer: economics. Even though the company sells some 4 billion coffee cups annually, the amount of paper used in their making barely accounts for a fraction of a percent of the total amount of paper produced in the United States. And any recycling program, be it plastic bottles or aluminum cans, relies on volume to make the capital investment (sorting equipment, balers, etc.) profitable.

In the case of Starbucks, these costs are further increased due to the plastic lining applied to each coffee cup to prevent leaks. Removing the plastic from the cups is a necessary step in the recycling process that only adds to the overall cost of the company’s recycling programs. And most paper mills will only accept Starbucks cups if the company can provide enough of them to make that extra step worthwhile.

Further complicating the company’s desires for a recyclable cup is the fact that its customers simply do not recycle enough of them to implement recycling in all of its stores. That, coupled with the small amount of paper material contained in the cups, makes it seem unlikely that Starbucks, and other purveyors of that delectable beverage, will ever attain a nationwide recycling program.

The only real way to make sure those billions of cups are recycled every year is to change consumer behavior. On that front, there are some promising signs. The country’s recycling rate continues to climb, albeit very slowly, and the modern climate of sustainability is encouraging many more consumers to recycle their waste. There is also the possibility of more sustainable materials being used in place of today’s paper cups, such as biodegradable paper or plastic. But for the time being, the best way to enjoy your cup of Joe might be to start bringing that old Thermos to the coffee shop.