General Biomass FAQ

Burning wood fuel

Q. What is biomass?

A. The term ‘biomass’ is shorthand for ‘biological mass’. It is fuel material derived from any biological (plant or animal) source. Woodfuel, is just one type of biomass from a list of many.

Q. What are the advantage of biomass over fossil fuels?

A. Biomass offers three main advantages over fossil fuels;

  • It can be significatly cheaper than heating oil.
  • It can generate significant annual payments for heat generated and used from schemes such as the Renewable Heat Incentive.
  • It is sustainable, renewable and significantly reduces your emissions. Biomass is carbon neutral as it releases the same amount of CO2 when burned as it has absorbed during its life.

Q. How many installs are currently operational in the UK with RHI?

A. There are over 4,500 Biomass boilers installed within the UK with RHI accreditation and with the help of Rainbow Heat and Power this number is growing every day.

Q. How efficient is a Lindner & Sommerauer biomass boiler?

A. The Lindner and Sommerauer boiler range efficiency varies from 95% down to 91.1%

  SL50 SL65 SL80 SL110 SL150 SL199 SL250

Max %


93.5 93.0 93.7 93.8 95.3 95.3

Min %

91.9 93.1 91.7 91.3 91.8 91.1 91.1


Q. What maintenance does a Lindner & Sommerauer Biomass boiler require?

A. We recommend that the boilers are serviced once every 12 months by a competent HETAS registered engineer and visually inspected once a week to check general wear and tear. Regular cleaning out of the ash bin to prevent blockages will also be required.

Q. Can a biomass boiler be connected to my current heating system?

A. Yes, both our Lindner and Sommerauer and Effecta Biomass boiler brands can be connected in the same way as a conventional boiler to run radiators, underfloor heating or warm air heaters.

Q. Do I need planning permission?

A. Unless your property is a listed building, you won’t need planning permission for the boiler itself. You may need planning permission if you;  plan to build a boiler house or fuel silo;  need to raise the height of your chimney above 1m or live in a Conservation Area or World Heritage Site and the flue will be visible from the road. If you are unsure if this applies to you, please check with your local planning officer. Whether or not planning permission is needed, all new installations should comply with local building regulations.

Q.  How do I decide on which size of biomass boiler I will need?

A. One of our team of experts will survey your planned site to assess your requirements, including boiler size and fuel type. During our visit we will take into consideration your building type and construction, your existing system along with your personal preferences to define the size, fuel type and energy output of your installation.

Q. What type of fuel can be burned?

A. We have put together the table below to give you a comparison of the calorific values of biomass fuels versus fossil fuels.

Fuel Net calorific value by mass GJ/Tonne Net calorific value by mass kWh/kg Bulk density kg/m3 Energy density by volume kWh/m3
Wood chips (30% moisture) 12.5 3.5 250 870
Wood pellets 17 4.8 650 3,100
House coal 27-31 7.5-8.6 850 6,400-7,300
Heating oil 42.5 11.8 845 10,000
Natural gas 38.1 10.6 0.9 9.8
LPG 46.3 12.9 510 6,600


Wood chips can be made from virgin wood or waste. Fuel-grade wood chips are normally between 3cm (G30) and 5cm (G50) in length. They can be purchased or self supplied if a ready source is available at a significant cost reduction as agaisnt heating oil.

1kg of wood chips generates 3.4kWh

Pellets are made from 100% natural wood (compressed shavings and sawdust) and are uniform in size and shape. Pellets are generally a clean, convenient fuel with a high calorific value and low ash content.

  • 1kg of pellets generates 4.9kWh
  • 2kg of pellets equates to 1 litre of heating oil.

Q. How much fuel do I need with my boiler?

A. As, with any heating system, the amount of fuel required depends on the size of the boiler and the heating demand of the property. The amount of fuel required also depends on the calorific value of the fuel and its density. For example, a 100kW boiler operating at 85% efficiency for 10 hours a day for 7 days would need:

Wood pellets

1.7 tonnes - requires 2.6m3 of storage

Woodchip 30% moisture content

3.7 tonnes - requires 12.2m3 of storage


Q. Where can I find someone to design my biomass system?

A. Right here! First of all, we'll need to discuss your project and get an idea of your fossil fuel usage. A site survey enables us to recommend a biomass heating system that fulfils your requirements. We will also invite you to visit an operational biomass boiler installation, where you can talk to the owners. Project management, delivery, installation, client training, commissioning, maintenance and RHI application assistance are just some of the things Rainbow Heat and Power can do  in order to meet your project's requirements.

Q. Can you install abroad?

A. No, sorry we only install in mainland UK.​

Q. How often do the fuels stores need filling?

​​A. This  depends on the fuel demand for the property and the size of your fuel store. The fuel store should be built to a size so that they only need to be refilled 3-4 times a year at the most.

Q. Can Biomass be burned in a smoke controlled area?

A. Approved biomass fuel can be burnt in a smokeless zone, check here to see if your project is located within one.

Q. Are the boilers fully automatically controlled?

A. ​Yes, our boilers use a Touch Screen Control panel, allowing you to regulate the temperature, fuel and automatic running of the boiler.

Q. What is so unique about the biomass boilers Rainbow Heat and Power supply?

A. Biomass boilers can significatly reduce fuel bills versus fossil fuels, they reduce C02 emissions by 96% and help you to gain RHI payments. The Lindner & Sommerauer range of boilers offer over 90% effiencies and are about as automated as possible. Rainbow Heat and Power offer complete project management, ensuring smooth installation of your biomass boiler.

Q. What type of flue is required for the boilers?

A. ​Twin wall stainless steel flue system is required for our biomass boilers.

Q. What is the lead time between placing the order to receiving my boiler?

A. Installation will normally take place 4 - 6 weeks after the deposit is received.

Q. Could the boiler be fitted by our own plumber?

A. Yes, but we have a team of expertly trained engineers at Rainbow Heat and Power and  recommend we install and commission the boiler. We will then carry out all safety checks and train you in the operation of the boiler. After installation we can continue this support.

Q. Do I need a special power supply?

A. You need a 16Amp power supply for all boilers. We also supply circuit breakers and triple phase adaptors.

Q. What warranty do you offer?

​​A. We offer 5 years warranty on the heat exhanger, 3 year on mechanical parts and 1 year on electrical.

Q. Can you burn plastic?

A. No, not under any circumstances!

Q. What are the benefits of using biomass as a sustainable fuel?

A. According to the Biomass Energy Centre, biomass is a renewable, low carbon fuel that is already widely available throughout the UK.  Its production and use also brings additional environmental and social benefits.  Correctly managed, biomass is a sustainable fuel that can deliver a significant reduction in net carbon emissions when compared with fossil fuels.

Q. Correctly managed, biomass is a sustainable fuel that can offer a wide range of benefits:

  • Biomass is a “carbon lean” fuel producing a fraction of the Carbon emissions of fossil fuels. click here for more details
  • Biomass can be sourced locally, from within the UK, on an indefinite basis, contributing to security of supply.
  • UK sourced biomass can offer local business opportunities and support the rural economy.
  • The establishment of local networks of production and usage, allows financial and environmental costs of transport to be minimized.There is no region in the UK that cannot be a producer of biomass.
  • The use of biomass fuel provides an economic incentive to manage woodland which improves biodiversity. click here for more details
  • Many biomass fuels generate lower levels of such atmospheric pollutants as sulphur dioxide, that contributes to 'acid rain'.
  • A. Biomass residues, co-products and waste not used for energy, or some other application will usually rot. This will generate CO2 in any case, and may also produce methane (CH4), a greenhouse gas 21 times more potent that CO2.