Typical freshly cut "green" firewood contains about 50% water by weight; for seasoned wood, the comparable figure is about 20%. Firewood is usually sold by volume, so compare the energy available from a given volume of green wood with that available from seasoned wood. Assume an energy content of 20 MJ/kg for perfectly dry wood, and that 2.3 MJ/kg of energy is needed to vaporize water. Also assume that the wood has essentially the same volume whether green or seasoned.

Typical freshly cut "green" firewood contains about 50% water by weight; for seasoned wood, the comparable figure is about 20%. Firewood is usually sold by volume, so compare the energy available from a given volume of green wood with that available from seasoned wood. Assume an energy content of 20 MJ/kg for perfectly dry wood, and that 2.3 MJ/kg of energy is needed to vaporize water. Also assume that the wood has essentially the same volume whether green or seasoned.