Last week, coffee drinkers learned about Starbucks’ latest sustainability initiative – a plan to phase out single-use straws by 2020. But Starbucks isn’t the only fast-food icon exploring ways to lessen its environmental impact. Together, McDonald’s and Starbucks distribute a combined 4 percent of the world’s 600 billion single-use cups annually. And, while the two fast food giants have been making strides toward sustainability separately for years, McDonald’s announced that it will be joining forces with the coffee icon to tackle an issue that outweighs the brands’ rivalry.