Wood
Wood has been used for heating for tens or perhaps hundreds of thousands of years. Though it is mankind’s oldest fuel source, its use has changed little over time: wood is stacked and burned, either on the ground or other suitable surface, or in a containers such as wood burning stoves or fireplaces, and is often ignited with the use of a highly combustible material serving as kindling. Today wood as a solid fuel is being increasingly looked on as an important source of biomass fuel, and thus an alternative to other less renewable power sources.
Firewood
Though waste wood can be collected from woodland areas, it is most common to purchase pre-seasoned logs for use as firewood and as fuel for use in domestic solid fuel heating: unseasoned wood burns poorly and tends to produce much more smoke due to its high water content. Logs can be purchased from many different outlets, such as garden centred or home improvement stores. Hardwood logs are generally more commonly available than softwood logs.
There are many different types of wood that can be used for firewood, or for use in solid fuel stoves or solid fuel central heating, though due to the different burning properties of different woods some are more popular than others. Ash is generally held to be the best wood for general purposes: it burns well, giving off both flame and heat, and even burns relatively well when green. Birch, pine and oak are also good, though the latter gives off little flame. If a pleasing scent is desired from a fire, then other more exotic woods are preferable. Cedar, apple, plum and walnut all give off a very pleasing scent in addition to burning well: the last of these is especially aromatic.
Wood Pellet
Wood pellets are an increasingly popular fuel for the owners of wood stoves and multi fuel stoves, for both efficiency and environmental reasons. Wood pellets are made from the refuse left over when wood is processed in a sawmill: whereas previously this waste wood was discarded, now it is processed and compacted to form wood pellets. Because they are made from processed waste wood and sawdust, wood pellets tend to burn very efficiently as they contain little moisture. Also, because of their small size they are generally easier to transport and use than standard hardwood logs. However, some stove owners prefer to use traditional logs, believing that using wood pellets does not give the authentic feeling of a roaring fire, and does not have the attractive scent that can be obtained by using certain woods.
Woodchip
Woodchip is another fuel derived from waste wood, and is an important biomass fuel. Though it comes from the same source as wood pellets, it is produced in a different manner: rather than pellets of compacted sawdust etc, larger, more natural-looking woodchips are the result. Though wood pellets produce more energy per gram (due to them being a compacted fuel source), woodchip is cheaper.
In areas with ready access to large quantities of woodchip, some coal power stations have been converted to use them as their primary fuel. This is being seen as a way to utilise biomass fuel in place of conventional fossil fuels in large-scale electricity generation.