About Wood Logs


There are typically three different types of wood logs that can be used for burning within wood boilers, being unseasoned logs , seasoned logs and kiln dried logs.

A seasoned log is one that has been cut and dry stored (i.e. under cover) for a long period of time, usually over 12 months.  These are very suitable for burning.  The moisture content after seasoning is typically around 30%.

Unseasoned logs are just that, unseasoned and recently cut.  They are likely to have high moisture content – i.e. above 50%.  Whilst it is possible to burn unseasoned logs on an open fire, it is not really advised to burn unseasoned logs within wood log boilers because the temperature is not sufficient to burn off the sap contained in the wood, which can then build up on the inside of the boiler as a tar condensate and lead to severe damage.

Lastly, Kiln Dried Logs are logs that have been put through a large kiln chamber that controls the temperature and humidity.  Moisture content is then typically around 20%.  The result is a wood log that burns hotter and for longer, due to the lower moisture content, resulting in even greater efficiency of your boiler.

Scoring or partial removal of bark may help to accelerate drying of wood logs.  For logs over 15 cm diameter splitting is recommended to assist drying.

The optimum size for wood logs should be around 25-30 cm long to be used within a wood log boiler.

Please see Table 3 within the “Biomass Energy Content & Price” section of the website for further details on wood logs.


Finally, it should also be noted that the intentional and controlled charring of wood and its incorporation into the soil is an effective method for carbon sequestration as well as an important technique to improve soil conditions for agriculture, particularly in heavily forested regions. It forms the basis of the rich soils known as “Terra preta”.