Tire recycling is the process of turning unusable tires into new items, burning them for fuel, or grinding them up to be used as filler. Ground-up rubber is usually used for paving and padding, but it can also be molded with plastic to create highly durable railroad ties.
Some people recycle tires by turning them into art sculptures or useful items, but most old tires are sent to a recycling center where they are treated with chemicals and broken down into a reusable material. The treated rubber is ground up, and some of it is set aside to be frozen with nitrogen and ground up finer into a powder. Most commonly, the ground up rubber is made into rubberized asphalt to pave highways and interstates, but since ground or "crumb" rubber is both durable and cushioned, it is also used as flooring for athletic courts and outdoor playgrounds.
Sometimes rubber is mixed with polyurethane to create boards that can resist extreme heat or cold and that last much longer than real wood. Some of the rubber from old tires is turned into usable rubber for new tires, or it may be shredded and melted and broken down to release energy or turned into an oily liquid that can be used as fuel.