A composition and method of storing and releasing fuel gas such as hydrogen, methane or natural gas is provided which utilizes lightly crosslinked high density polyethylene pellets. Fuel gas is stored by placing the pellets in a reaction chamber which is heated to a temperature slightly above the crystalline melting point of the pellets, followed by the introduction of fuel gas into the chamber. The fuel gas permeates the pellets and becomes contained therein upon cooling of the pellets under pressure. The fuel gas may be stored indefinitely in the pellets at ambient temperature. When release of the fuel gas is desired, the pellets are incrementally metered into a discharge chamber and are heated to a temperature above the crystalline melting point of the pellets under a pressure from about 5 to 200 psi such that the fuel gas is released from the pellets for use. The expended pellets may then be recycled for further fuel gas storage.