Biomass Boilers

Biomass Fuel Types

What is Biomass?

Biomass energy is stored in living organisms, usually derived from the photosynthesis process. Both animal and vegetable obtained material can be a source of biomass. Biomass is carbon based, it also contains other naturally organic molecules including oxygen and hydrogen. 

The carbon used to create biomass is taken from the atmosphere in the form of carbon dioxide (CO²) found in plant life. This plant life may be consumed by animals therefore converting into animal biomass. 

While carbon is growing, biomass takes it out of the atmosphere and returns it when it is being burned. Renewable Energy Biomass can be constantly replenished if managed on a sustainable basis. Consequently there is no net increase in the level of CO2 omissions by using a Biomass Boiler. 

Windhager log biomass boiler with buffer store

Biomass Boiler Types:

Pellet boilers: Selected boilers come equipped with an integral pellet hopper, this is repeatedly topped up manually or automatically from larger store. To supply fuel for a week or more some boilers have an integrated silo, ‘Flexibags’ or external silos can hold fuel for 2-12 months. Generally installed in utility room and cellars, domestic models range from 8-65kW. 

Log boilers: Will not need stoking as frequently as a log stove but are loaded by hand. Domestic models range from 20 – 50kW and are generally located in a separate boiler room. Log boilers are intended to work alongside a large heat store known as a buffer tank or accumulator. This improves its efficiency by allowing it to operate for shorter periods at higher loads.

Chip boilers: Do not work effectively below 50kW and work in a similar way to pellet boilers. Therefore they are not suitable for single domestic use, however a good option for community heating schemes and larger buildings. 

Grant Spira 26kw Biomass Pellet Boiler

Is wood derived biomass suitable for my property?

A wood fuel heating system can be effectively integrated into an existing hot water and central heating system but will need to meet certain requirements.  

Ventilation and Flues: To disperse the combustion gases you will need a permanent vent to provide sufficient air for the appliance and a suitable flue. Space: A Fuel storage area needs to have easy access for deliveries and most important be dry and moisture free. For deliveries in the coldest time of year the storage space needs to have space for the fuel you think you will use in between deliveries and a little more.  

Permission: All wood heating systems have to comply with Building Regulations. If you live in a ‘smoke control zone’ ‘exempted’ appliances are required.


Wood fuelled boilers, room heaters and stoves need to be kept clean and swept on a regular basis to remove ash. The ash bin will need to be emptied on a weekly basis. A log fire requires ash removal before every use 

Automated biomass boilers will have a built in self-cleaning system; this will collect ash from the heat exchange tubes and combustion gate. Some boilers have a mechanism to compress the ash which reduces the amount of times the ash bin needs emptying. The boiler will need to be shut down periodically whilst being cleaned by hand if it does not have an automated ash cleaning mechanism. If the ash is not cleaned out regularly, the build up will adversely affect the combustion conditions and consequently lead to boiler failure.  

The only maintenance requirement for the cleaning for the heat exchanger and the automatic ash removal will be an annual service.  

A flue pipe must be swept regularly to prevent blockages and remove all soot deposits. 

Biomass Boiler Wood Pellet Delivery

Running Costs

Biomass boilers provide the best savings when compared to heating systems which use electricity, oil, coal or transported gas, with average savings of over 30%.

When compared to a properly installed, well maintained high efficiency mains gas based heating system, a biomass boiler will generally be more expensive to run unless the homeowner has their own source of fuel.

Renewable Heat Incentive Calculation

Renewable Heat Incentive (RHI)

The Renewable Heat Incentive is a government backed scheme which provides a set payment for every kilowatt hour (unit) of renewable heat required to heat and provide hot water into a property. In most cases this is deemed from an Energy Performance Certificate, but under specific circumstances it is metered.

Once the system is installed and registered  payments are made quarterly over a period of seven years. On average the RHI will pay for the cost of the installation and support some of the running costs.

Biomass Boiler Manufacturers

Okofen (ÖkoFEN)

Okofen Pellematic Biomass boiler

ÖkoFEN is Europe’s specialist in pellet heating systems, with a modern production facility and several hundred employees. ÖkoFEN paved the way for pellet heating technology with 60,000 installed systems, subsidiaries in 17 countries worldwide, and groundbreaking innovations justify the decision to specialise in pellets. More:


Windhager Biowin Biomass Pellet Boiler

Manufactured and developed in Austria to the strictest of quality control processes and using only high quality materials, Windhager products constantly deliver durability, reliability and efficiency. A pioneering company renowned for design and manufacturing of leading edge, innovative biomass boilers. More:

Biomass Boiler Service and Maintenance