How does a metal roof rank from an ecological viewpoint? Steel is the most recycled metal on earth and can be reused almost indefinitely without compromising its quality or strength. This environmentally friendly material is 100% recyclable - shingles: zero percent. According to the National Association of Home Builders, shingle roofing materials make up more than 5% (1.36 billion pounds) of the waste dumped in landfills each year. In addition, over ten million barrels of oil are used each year in the production of new shingle roofing materials.