When humans move into new territory, we leave waste behind, and one of our most harmful byproducts is plastic. Dave Hakkens wants to solve the planet's plastic problem with a build-it-yourself home recycling system that will make the material easy to reuse.

"With wood or metal, you can recycle it yourself," he says. There are already consumer tools that can cut, bend, melt, and reconnect scraps of this ­material. The machines that process ­plastic for recycling, on the other hand, are not ­available in your average workshop.

So Hakkens decided to design those ­machines himself. His Precious Plastic system includes four appliances: One chops up and shreds clean plastic refuse into scraps. The other three heat and ­reuse that plastic by squeezing it into filament for 3D printers, injecting it into a mold to form small objects, or compressing it into a mold to make larger items.