The Science Behind The Seasoning of Wood
Most stove owners know only too well the importance of only burning seasoned wood.
The benefits are huge.
Not only does burning seasoned wood reduce pollution, but you also get a much better heat output and efficiency level from your stove.
Here is a deeper insight into the science behind burning seasoned firewood.
Seasoning firewood is an important process that involves drying and curing wood to prepare it for burning. While the term “seasoning” might seem simple, it actually involves several complex changes that occur within the wood as it loses moisture and becomes more suitable for use in a wood-burning stove. Understanding what happens during this process can help you make the best choices when selecting and preparing your firewood.
When freshly cut, wood contains a significant amount of water, which can be as high as 50% to 60% by weight. This high moisture content makes the wood difficult to burn and inefficient as fuel. When wood is seasoned, it is allowed to dry out, which reduces its moisture content to around 20% or less. This is the ideal moisture level for burning as it allows the wood to ignite easily, burn hotter, and produce less smoke.
Here is the science:
Several chemical and physical changes take place during the seasoning process:
1. Evaporation of Moisture
The primary change that occurs when wood seasons is the evaporation of water from the wood. Freshly cut wood has a high moisture content because the tree’s sap, which contains water, is still present. As the wood dries out, water begins to leave the cells of the wood through evaporation. This moisture exits both through the surface and the ends of the logs, which is why splitting wood into smaller pieces helps it season faster.
2. Breaking Down of Lignin and Cellulose
Lignin is the substance that gives wood its structure and rigidity, while cellulose is the material responsible for the wood’s strength. As the wood dries, some of the lignin in the wood breaks down, making it more brittle and easier to burn. However, the process is gradual, and too much moisture can prevent the lignin from properly breaking down, which is why seasoning is essential.
3. Reduction of Volatile Compounds
During the drying process, some of the volatile organic compounds (VOCs) in the wood evaporate. These VOCs are responsible for the strong smells that fresh-cut wood often has. When the wood seasons, the reduction of VOCs leads to a cleaner, less pungent burning experience.
4. Wood Shrinkage and Cracking
As the moisture leaves the wood, the wood shrinks. This shrinking can cause cracks and splits to form, especially at the ends of the logs. These cracks are often referred to as “checking,” and they are a natural part of the seasoning process. While checks do not necessarily harm the burning properties of the wood, they do help moisture escape faster, further accelerating the seasoning process.
Storing Firewood:
As a general rule, freshly cut wood, to be seasoned, should not be stored inside. However, firewood should be bought inside one day before it is to be burnt. Outdoor woodsheds are ideal for storing wood, although not all households have the space for this. If you don’t have a woodshed, then make sure where you store the wood is in a dry, well-ventilated area, which is protected from dampness and rain. You should also allow air to be able to flow in, under and around the logs. Cross-stacking wood is best. Do not stack too high unless the wood is supported by a damp-free wall.
Car garages are not ideal for storing wood due to the fire risk. Firewood should also not be stored directly on top of the ground without supporting logs, as this can trap moisture. The key to the successful storage and seasoning of logs is ensuring they are kept dry and have adequate air circulating around them. In warmer months, such as the summer, the speed of seasoning will increase due to the increased warmth.
If you are making the move to a wood-burning stove, it’s never too late to start seasoning your own wood. Starting now and gathering your own firewood means in a year or two, depending on the wood you gather, you will have a nice supply of wood to keep you warm.
