Many urban firewood users purchase processed wood because of its convenience, availability and deliver-ability. It takes a lot less room to store the wood and is usually processed to fit the fireplace or stove. Processed firewood comes at a premium cost which is associated with preparation, handling and transportation. You need to acquaint yourself with the value of firewood in your area and pay a fair price. You can find plenty of great dealers online and in the phone book.
Easiest Wood to Split:
Various woods have different splitting characteristics which are important to consider. Some woods split with little effort while others can be tough, stringy, and difficult to split. Tree species to avoid because of splitting difficulties are elm, sycamore and gum. Tree species especially easy to split are most conifers, oaks, ash and hard maple.
Woods with interlocking grain like elm, gum or sycamore are to be avoided and are difficult to split even with a mechanical log splitter. One rule of thumb should also be remembered - green wood will split more easily than dry wood. Also, softwoods will generally split more easily than hardwoods.
How Wood Burns:
In the first stage, wood is heated to the point where moisture within the wood cells is driven off and the cells are drying out. As the wood is losing moisture, it is chemically changing into charcoal - which is famous for its volatile gases and liquids. Stopping the process at this point is where the charcoal industry packages their products.
The second stage is where actual flames burn off the volatile gases and volatile liquids to the point where charcoal has lost most of these volatile fuels. Much of the energy of wood fuel is lost during this stage and where premium wood burning systems can improve their efficiency.
Finally, the third stage occurs when the charcoal burns and can be seen when the embers glow. This is called "coaling". At this point, heat is radiated from the burning bed of coals. Different species of wood burn and expend energy differently throughout these three stages.
The point to be made here is that a good firewood species should be dry, should burn through the second stage without sparks with a minimum of smoke production, and spends a long time burning in the third "coaling" phase.
Wood That Burns Best:
Most of us don't realize that air dried wood will produce about 7,000 BTU’s per pound regardless of the species - all wood burns with the same value. The catch 22 here is in the density variation between different species which can be significant.
As an example - one unit of heavy oak wood will produce roughly as much heat as two units of cottonwood when measuring BTU output. So lighter woods like cottonwood and willow will produce the same heat per pound as the heavier oak and hickory woods. This means that a greater volume of cottonwood is needed than oak to produce the same amount of heat.
Other things to consider is that some species of wood start easier than others but give off more smoke and more sparks than others. Easy starting wood is not necessarily the best wood to use for heating. Remember that different species of wood will last longer and have better coaling qualities than others. It is important to consider these factors when selecting firewood.
The Needle and the Leaf Debate:
On the positive side, conifers are easier to ignite because they are resinous. Still, these softwoods tend to burn rapidly with a high, hot flame and burn out quickly, requiring frequent attention. Finding a wood heating unit that can store this quick heat and distribute it through time is critical.
Red cedar and other trees with high-resin will often hold "moisture pockets" which can be both irritating and dangerous without the proper burning hardware. These trapped gases will cause a pop when heated sending out sparks. This can present a significant fire risk, especially when burned in open fireplaces without screens.
Hardwoods will burn longer but less vigorously when compared to softwoods. The wood is harder to start and conifers are often used to kindle the wood burning process. The reason hardwoods make the best fuel is because they tend to produce more coals, a process called "coaling", that last longer than softwoods. Well seasoned oak makes an excellent fuel because it produces a uniformly short flame and provides heat preserving coals.