Plastic bottles are a blight, but some folks are putting them to great use.

In the Philippines, Isang Litrong Liwanag has had great success putting MIT’s Solar Bottle Bulbs to use. Their homes are packed together tightly and aren’t always wired for electricity, but the bulb costs no money to operate and is incredibly cheap to build and install. How Stuff Works’ blog explains more (as does the video below):

Here’s the setup: The plastic water bottles are cleaned, filled with water and bleach, and tucked snugly into holes cut into a roof. When sunlight hits the bottle, the water refracts the light and provides about as much illumination as a 50-watt light bulb.

In Guatemala, Hug It Forward has figured out how to build schools for under $10,000 using plastic bottles and garbage. Good explains how they do it:

The plastic bottles are stuffed with trash, tucked between supportive chicken wire, and coated in layers of concrete to form walls between the framing. The bottles make up the insulation, while more structurally sound materials like wood posts are used for the framing.