Firewood was the primary source of fuel until the 1800s, when it was displaced by coal and later by oil. Firewood is a renewable resource, provided the consumption rate is controlled to sustainable levels. Today firewood is usually obtained from timber or trees unsuitable or unwanted for building or construction. In the United States, firewood is sold by the cord, and is therefore also called cordwood.
Of all of the renewable resources, only biomass, including wood, and geothermal need to be carefully managed in order to prevent depletion. The shortage of suitable firewood in some places has seen local populations damaging huge tracts of bush thus leading to further desertification. On the other hand, proper forestry practices applied to firewood allow the usage of a carbon-neutral, or even carbon-negative, energy source, since the carbon dioxide released by the burning of the firewood was previously absorbed from the ambient atmosphere through photosynthesis. Because of this, firewood can be considered to be a form of solar energy.
Some firewood is harvested in "woodlots" managed for that purpose, but in heavily wooded areas it is more usually harvested as a byproduct of natural forests. Deadfall that has not started to rot is preferred, since it is already partly seasoned. Standing dead timber is considered better still, as it is both seasoned and has less rot. Harvesting this form of timber reduces the speed and intensity of bushfires. Harvesting timber for firewood is normally carried out by hand with chainsaws. Thus, longer pieces - requiring less manual labour, and less chainsaw fuel - are less expensive and only limited by the size of their firebox. Prices also vary considerably with the distance from wood lots, and quality of the wood.
Normally wood is cut in the winter when trees have less sap so that it will season more quickly. Most firewood also requires splitting, which also allows for faster seasoning by exposing more surface area. Today most splitting is done with a hydraulic splitting machine, but it can also be split with a splitting maul.
In the United States, firewood is usually sold by the cord, 128 ft³ (3.62 m³), corresponding to a woodpile wide × high of 4 ft-long logs. The cord is legally defined by statute in most states.
Using 4 mil plastic it is possible to create a greenhouse effect and decrease the amount of time needed to season the firewood. See the link below.
The energy content of a cord of wood depends on the type of wood, and ranges from 15.5 to 32 million Btu per cord.
Under a roof: Here are no concerns about the wood being subjected to rain, snow or run-off. The methods for stacking depend on the structure and layout desired. Whether split, or in 'rounds' (flush-cut and unsplit segments of logs), the wood should be stacked lengthwise, which is the most stable and practical method.
Outdoors: Firewood should be stacked with the bark facing upwards. This allows the water to drain off, and standing frost, ice, or snow to be kept from the wood. When possible, a tarp or water-proof cover may be placed over the top of the pile. This can be a large piece of plywood or an oiled canvas cloth, although cheap plastic sheeting may also be used.
A holz hausen, or "wood house", is a circular method of stacking wood which results in accelerated drying and a small footprint. A traditional holz hausen has a 10 foot diameter, stands 10 feet high, and holds about 6 cords of wood. The walls are made of pieces arranged radially, and tilted slightly inward for stability. The inside pieces are stacked on end to form a chimney for air flow. The top pieces are tilted slightly outward to shed rain and are placed bark side up. If constructed correctly, this method of stacking can produce seasoned firewood in as little at 3 months.