The manufacturing of our polypropylene #5 cups requires less resin than that of high-density polyethylene #2 cups. So less energy (electricity and gas) and fewer resources are used to produce our #5 cups. And because they have thinner walls, #5 cups make less waste than #2 cups. Although #5 cups are less often accepted at recycling centers, their overall environmental impact is less than that of #2 cups.
We used to package our yogurt in #2 cups because we thought this was the most recyclable material. But we learned that many recycling centers cull #2 cups from their recycling piles, recycling only the bottles and sending the cups to landfills. This is because bottles and cups have different melting points and can't be recycled together.