Biomass Stoves & Boilers

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High efficiency biomass stoves, heaters and boilers use the cheapest and the most environmentally friendly fuel available on the market in Bulgaria


Biomass is organic matter produced either directly from plants or indirectly from industrial, commercial, domestic or agricultural products. The CO2 released when energy is generated from biomass is balanced by that absorbed during the fuel’s production; hence the biomass fired systems are considered as carbon-emission neutral and environmentally friendly.


Biomass is often called ‘bioenergy’ or ‘biofuels’. The biofuels fall into two main categories:

  • Woody biomass – includes forest products, untreated wood products, short rotation coppice (SRC), e.g. willow.
  • Non-woody biomass – includes animal waste, industrial and biodegradable municipal products from food processing and high energy crops, e.g. rape, sugar cane, maize.

For the small-scale domestic applications approved by the REECL Programme, the biomass fuel usually takes the form of woody biomass – wood logs, wood chips and wood pellets. There are two main ways of using biomass to heat a domestic property:

  • Stand-alone stoves – These can be fuelled by logs or pellets but only pellets are suitable for automatic feed. Generally they are 6-12 kW in output. Biomass stoves and fires can be up to 80% efficient. They are normally used for background heating. They also add aesthetic value in the living area of the house itself. Many wood burning stoves act as space heaters only. But the higher output versions can be fitted with an integral back boiler and/or solar heaters to provide domestic hot water and central heating through radiators.
  • Boilers – These are suitable for pellets, logs or chips, and are generally larger than 15 kW. There is a wide range of domestic biomass burning central heating boilers available on the market in Bulgaria. Most common are the log boilers, which must be loaded by hand and may be unsuitable for some situations. Automatic pellet and wood-chip systems can be more expensive. Many boilers will dual-fire both wood chips and pellets, although the wood chip boilers need larger hoppers to provide the same time interval between refuelling.

Both biomass stove and boilers can be designed with an integral hot water energy storage or accumulator tank that stores water up to 90°C, enabling the supply of heat to be further decoupled from the combustion of the fuel. This is particularly helpful with log boilers where systems operate at full load and the matching of demand with load is performed by the accumulator. You should consider the following issues if you are thinking about a biomass boiler or stove:

  • Fuel – It is important to have storage space for the fuel, appropriate access to the stove/boiler for loading and a local fuel supplier.
  • Flue – The vent must be specifically designed for wood fuel appliances and there must be sufficient air movement for proper operation of the stove.
  •  Capital costs – These depend on the type and size of system. Stand alone room heaters and stoves are generally the cheapest while boilers tend to be more expensive. The boiler costs vary depending on the fuel choice, for example a typical 20kW pellet boiler would cost slightly more than a manual log feed system of the same size.
  • Running costs – Fuel costs generally depend on the distance from your supplier. As a general rule the biomass will stay one of the cheapest fuels on the Bulgarian market.
To get the most out of your new biomass fired heating system think about combining it with new modern controls and instrumentation.

Appropriate controls let heating systems react to changes in temperature, provide different levels of heat in different rooms and switch hot water on and off at whatever times are specified by the homeowner. Well-designed heating control systems will pay for themselves in less than four to five years.

Key Benefits to the Households and Local Communities of Using Biomass Systems:

  • Producing energy from biomass has both environmental and economic advantages to the householders and their communities.
  • Biomass is currently the cheapest fuel on the market in Bulgaria.
  • It is most cost-effective when a local fuel source is used, which results in low fuel costs, local investment and employment.
  • Biomass can contribute to waste management by harnessing energy from products that are often disposed of at landfill sites.

 To select the most appropriate biomass-fired heating system and associated controls for your home, you are advised to contact a certified HVAC consultant to help you with determining the most suitable technical solution for your home assessing its size, construction type, geographical location and your heating requirements.