Peat is an accumulation of partially decayed vegetation or organic matter that is unique to natural areas called peatlands. The peatland ecosystem is the most efficient carbon sink on the planet because peatland plants capture the CO2 which is naturally released from the peat maintaining an equilibrium.

Peat is harvested as an important source of fuel in certain parts of the world. By volume, there are about 4 trillion m³ of peat in the world covering a total of around 2% of global land area (about 3 million km²), containing about 8 billion terajoules of energy.