TO PLACATE shareholders and shoppers, American companies are promising to use more recycled materials in their products. It’s a nice idea, but surprisingly hard to achieve. Coca-Cola committed to using at least 25% recycled plastic in its containers by 2015, but revised this downwards owing to scarce supply and high costs. Walmart is struggling to find the material to meet its goal to use 3 billion pounds of recycled plastic in its packaging and products by 2020. “The problem is supply,” explains Rob Kaplan of Walmart.