High-density polyethylene ( HDPE) or polyethylene high-density ( PEHD) is a polyethylene thermoplastic made from petroleum. It takes 1.75 kilograms of petroleum ( in terms of energy and raw materials) to make one kilogram of HDPE. HDPE is commonly recycled, and has the number " 2" as its recycling symbol. In 2007, the global HDPE market reached a volume of more than 30 million tons.