Over half the people on earth (3 billion people) rely on fire wood directly for essentially all their daily energy needs such as cooking and heating. Though burning wood is sustainable in small quantities within a sustainable relationship with the ecosystem, burning in too much quantity degrades the land. Moreover, with the increase in the price of fossil fuel, more and more people will turn to fire wood for energy, causing further pressure on our trees and ecosystems precisely when we need our trees and ecosystems to heal the damage caused by fossil fuel burning.
Also, for the over 3 billion people that rely on fire wood for cooking, often this done indoors and the smoke causes serious health problems for the (usually) women that keep the hearth as well as accompanying children. In some places plastic and tires are also burned for cooking which causes even more diseases.
However, when 1 kg of wood is turned into 400 grams of charcoal, 50 % or more energy is extracted from the 400 grams of charcoal than if we burn the 1 kg of wood in the average fire [1].

Techniques