How do biomass boilers work?

Wood is hardly a new fuel for heating houses, but the technology has
improved considerably to make it more efficient. Open fires may look
lovely, but they are not a good way to heat a room. Most of the heat
goes up the chimney and, as the fire draws in oxygen to burn, it creates
draughts in the room that can cancel out the benefit of the heat.

 
Modern wood-burning stoves are a huge improvement on the open fire for
room heating. They convert 70 per cent of the fuel into useful heat. If
you attach a back boiler, they can also help heat water and supply some radiators.
 
More efficient still are automatic pellet stoves which operate at 85 to
90 per cent efficiency. They spread the heat through convection, rather
than traditional radiation, which means the room is heated more evenly
and efficiently using a fan. They are clean and easy to use, with
automatic ignition and a thermostatic control. They have an integrated
hopper, which automatically tops up the fuel. They generally hold enough
fuel for one to three days operation. The ash pan needs to be emptied
about once a month. It is also possible to add a back boiler to these.
 
Biomass boilers can replace oil or gas boilers to heat hot water and
radiators (or under floor heating). They burn logs, wood chips, wood
pellets or other forms of biomass. The most advanced boilers are fully
automatic. They control the amount of fuel and air supplied to the
combustion chamber. As a result they are highly efficient and emissions
are low.
 
They are fed with wood chips or pellets from a large hopper sited
nearby. If you’ve got space, manufacturers recommend a hopper that’s big
enough to hold a year’s supply of fuel. This minimises transport and
delivery costs for fuel, as well as work for the owner. Maintenance is
minimal – although you will need to clean it and remove the ash about
once a month. If that isn’t possible due to space or budget, you can get
wood pellet delivered on pallets of 10kg bags, from which you manually
fill a smaller hopper.
 

At the other end of the scale, log-fed boilers are more suitable for
people with ready access to a supply of wood, and time to cut it to the
right size. These will need more time spent on feeding them with fuel
and cleaning out the ash.

Read More: Wood Pellet Boilers