The U.S. discards 13 million tons of plastic annually — more than 12% of our overall waste — and barely 7% of the plastic we discard is recycled. The biggest proportion of that plastic waste comes in the form of plastic bottles (beverages as well as personal care products, cleansers and the like) and packaging. How about a plastic bottle greenhouse? Or a colorful outdoor wall? That’s what this sewage treatment plant in Scotland tried, to great effect: