Natural Capital: Those goods and services that are not manufactured but have values to human, e.g. Soil, water, trees, living organisms etc.

Non-renewable energy: exist in finite amount and are not renewed after they have been depleted, e.g. fossil fuels. These are forms of stored solar energy produced by photosysthesis (coal) and remains of organic life from millions of years ago, now being extracted and burned by humans.

Renewable energy: they can be used over and over again and are considered to be sustainable, e.g. Solar, wind, geothermal energy etc.

Replenishable resources: are middle ground between renewable and non-renewable resources. They tend to be replaced over a long period of time. If the depletion rate is larger than recharge rate, the natural capital is depleted. E.g. Fuel wood.

Click here for types of renewable and nonrenewable energy resources


History of Energy Resources
Alternative energy
Energy resources of the future