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How do Biomass Boilers Work?


Biomass boilers are a modern replacement for oil and gas boilers which enable you to heat hot water, radiators, and under floor heating.

Biomass boilers 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 a combustion chamber and as a result they are highly efficient with very low emissions.

Typically a large hopper will feed wood chips or pellets to the boiler. The hopper can be as big or as small as the space you have available next to the biomass boiler. Naturally the larger the hopper, the less transport and delivery fuel costs and less frequency for you to refill.

Alternatively, log fed boilers are more suitable for people with access to a supply of wood, and the time to cut the wood to the right size. Wood boilers require much more time to feed them with fuel and to clean out the vast amounts of ash.

Your central heating system and hot water cycle simply flows through the biomass boiler and the heat from the boiler will transfer to the water and central heating system.

Biomass boiler are self lighting and fully controllable in that they will only burn the amount of fuel required to provide the heat demand at that time i.e. if your central heating system is already hot then it will only burn a small amount of fuel to top up the system or it will shut off and re-start when required.


Which fuel is best for Biomass Boilers?

Biomass boiler fuels need more storage space than fossil fuels i.e. oil and LPG.

The three types of fuel most commonly used for boilers are logs, wood chips and wood pellets.

PelletsWood Pellets are typically made from compressed sawdust, wood shavings, and other biomass products and are nearly perfectly uniform in shape and size. They have higher energy content and as such take up less storage space than logs and wood chips. Wood pellet biomass boiler systems are the smallest, neatest and most like a mainstream boiler and require the least input from the user. Wood pellets can be used in automated feeder systems using a hopper storage bin.


Wood ChipWood Chips are the least expensive and most abundant of the three materials for biomass boilers. They allow for more mechanisation than logs, but are not as efficient as wood pellets. It’s very important that they near to the same size to ensure that they work smoothly in an automated boiler feeder system.  Wood chips can be used in automated feeder systems using a hopper storage bin.


LogsLogs are typically fast grown locally sourced quick drying sustainable timber. However to ensure that your boiler is efficient it important to get the moisture content of the logs right; ideally logs will have a moisture content of less than 25 per cent or they simply do not output sufficient heat and will create smoke and tar within the boiler. Logs are usually manually fed into the boiler although top quality system offer a hopper fed system however all the logs must be sawn to exact length.



A hopper is simply a storage bin that feeds the boiler on demand. If you don’t have a hopper, you will have to load bags of pellet or wood chip manually into the boiler. How frequently you do this depends on the size of your biomass system.

The supply, storage and handling of your fuel type must be thought out carefully before you purchase a biomass boiler.


What is the difference between a Boiler and Stove?

Biomass Boilers can be used in place of a standard gas or oil boiler to heat radiators and to heat hot water. Biomass boilers are typically larger than the gas or oil or LPG boilers. Financially they are generally more suited for homes on oil or LPG.

Stoves are used to heat a single room, usually in conjunction with other heating systems i.e. gas or electric radiator systems, but may also have a back boiler to provide hot water.

Wood burning stoves are suitable for heating any room providing there is a chimney or a flue. They come in different shapes and sizes, and can burn logs, or wood pellets. The wood pellet stoves tend to be cleaner and easier to maintain, producing much less ash.

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