Renewable Biorefineries

1. Renewable resources

A renewable resource is a substance that can be replaced or replenished. Some renewable resources provide continuous supply, such as solar energy, wind energy and geothermal pressure, while other resources are considered renewable even though some time or effort must go into their renewal, such as wood, oxygen, leather and fish. Some precious metals are also considered renewable even though they are not naturally replaced, they are not destroyed during their extraction and use so they can be recycled. A renewable resource is different from a non-renewable resource, as once a non-renewable resource is used, it is depleted and cannot be recovered.