Which Fuel is Best for Biomass Boilers
All wood fuels need more storage space than fossil fuels (oil or LPG).
The three types of fuel most commonly used are logs, wood chips and wood pellets.
Of these, the latter two can be used in automated systems and stored in
a hopper. Logs must be manually fed into the boiler and they are less
automated, so their efficiency is more dependent on human input. If the
wood isn’t adequately seasoned or contains too much moisture, or if the
air supply is reduced too early, they will not burn as well and will
create smoke and tar.
pellets are made from compressed sawdust and wood shavings and other
biomass products and are uniform in size and shape. They have a higher
energy content and so take up less storage space than logs or wood
chips. Stove and boiler manufacturers specify the size, shape and
moisture content their products need to perform well. Wood pellet
systems are the smallest, neatest and most like a mainstream boiler and
require the least input from the user.
Wood chips are cheaper and abundant. They allow for more mechanisation
than logs, but are not as efficient as wood pellets. It’s important that
they are pretty uniform in size to work smoothly in a automated
If you don’t have a hopper, you will have to load sacks manually into
the boiler or stove’s feed system. How frequently you have to do this
will depend on the system you choose. Not all suppliers are able to
supply loose pellets.
It’s important to think through carefully the supply, storage and
handling of fuel before you invest in a biomass boiler. There is
generally some trade offs between each element, and they will be
specific to your site. You need to consider ease of access for the fuel
delivery and how you are going to get fuel to the boiler.
To maximise the efficiency of your appliance it’s important to get the
moisture content of the fuel right. Ideally logs and wood chips will
have a moisture content of less than 25 per cent. Wood pellets need to
be dryer – at around 8 per cent moisture.
Read More: Wood Pellet Boilers