A non-renewable resource (also called a finite resource) is a resource that does not renew itself at a sufficient rate for sustainable economic extraction in meaningful human time-frames. An example is carbon-based, organically-derived fuel. The original organic material, with the aid of heat and pressure, becomes a fuel such as oil or gas. A renewable resource is a resource which can be used repeatedly because it is replaced naturally. Examples are: oxygen, fresh water, solar energy, timber, andbiomass. Renewable resources may also include goods commodities such as wood, paper and leather.