Logs

What is the calorific value of logs?

Around 5kWh per kg, depending on moisture content and type of wood (hardwood or softwood, and species).  For a batch-burning boiler, the ideal size is 50cm in length, 12-15cm in thickness.

What kind of logs should I burn?

Logs should be sustainably sourced, seasoned for between 1-2 years to ensure below 20% moisture content and fuel that is free from coatings and preservatives. Unseasoned or wet logs burn inefficiently, reducing the heat produced, and instead produce excessive soot and tar which can cause flue fires. Moisture levels are best tested with a handheld moisture meter.

How long do logs take to dry?

Hard woods will take longer to season (two years) than soft woods (one year).

Where can I find a good log supplier?

The Biomass Suppliers List (BSL) includes the most comprehensive list of high quality wood fuel suppliers in your area.

The table below compares logs and other forms of heating fuel.

A table that lists volume, CO2 emissions and kilowatt hours per kilo of various different biomass fuels

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