How do I store wood biomass?

Logs should be stacked and stored in a covered but well-ventilated place for at least one year, preferably two, to air-dry the wood to a moisture content below 30%. An open-sided wood store would be suitable, a garage wouldn't. Bringing logs inside for the last week or so improves them to room dryness. (Stoves might be specified to cope with 50% moisture content, but efficiency will suffer)

The required storage space depends on how big and how well-insulated your home is. A small cottage is likely to need 8 cubic metres (m3) of logs each year, a 3-bedroom house 12m3, and a large detached house 16m3.

Pellets have a higher energy content and so take up about half as much space; a 15kg bag should last a few days. Depending on the system you can have these piped straight into a hopper or delived in bags to store in the shed or garage. To compare to an oil storage tank, pellets have about half the energy density of heating oil, so for the same amount of energy, about twice as much volume of pellets is needed as with oil.

Larger systems (for example a school or a block of flats) can use wood chip - this allows more automation than logs and is cheaper than pellets. A wood chip boiler heats several buildings at CAT; seasoned wood is delivered, chipped, and stored until it reaches 15% moisture content. For larger schemes, it’s a good idea to have a supply contract with a trusted supplier to ensure a consistant and dry supply of wood.


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