Biomass boiler: What is it & how much does it cost?

Are you wondering if you should replace your conventional boiler with a biomass boiler? Read on to discover the pros and cons of having a biomass boiler so that you can decide if you should get one for your home.


What is a biomass boiler?

A biomass boiler uses fuel developed from organic materials, such as wood and plants, to produce heat. This heat can then be used to warm our homes and even generate electricity.

Instead of burning gas or oil to produce heat, a biomass boiler combusts sustainably sourced materials. No matter if these materials are sourced from plants or animals, they’ve all absorbed chemical energy from the sun.

The following are the most common fuels for a biomass boiler:

  • Wood (logs, chips or pellets)
  • Straw
  • Animal waste
  • Agricultural waste
  • Crops

Even though a range of fuels can be used, different biomass boiler types require different biomass fuels. If you use the wrong type of biomass fuel, it could result in the following:

  • Safety issues
  • Boiler damage
  • Boiler inefficiency
  • Excessive emissions
  • Blockage in the feed hopper

Biomass boilers tend to be much larger than other types of boilers. This is because the boiler needs to be large enough to hold a large amount of fuel, such as wood pellets. You may also choose to install an automatic feed hopper, which would take up even more room.

What is an automatic feed hopper?
This hopper stores wood pellets or other biomass materials that are automatically fed into the boiler when needed. This makes it so you don’t need to refuel the boiler very often.

Biomass boiler types

Let’s have a look at the most common types of biomass boilers.

  • Fully automated biomass boiler — With this type of biomass boiler, the wood is automatically fed from a hopper (or sometimes a silo) into the boiler’s combustion chamber.

  • Combined heat and power (CHP) biomass boiler — CHP boilers generate both heat and electricity. These are more suitable for larger businesses.

  • Semi-automated biomass boiler (residential) — These boilers are smaller in size and designed for residential properties. Their appearance resembles a standard log burner and they have recently become much more popular in smaller homes.

  • Semi-automated biomass boiler (industrial) — These boilers come with a hopper that can hold a reasonable amount of fuel. It will, however, need to be manually replenished more often. These boilers are cheaper than fully automated units.

  • Log-fed biomass boiler — These units are appropriate for those with access to firewood. They can be rather time consuming as they must be fed by hand. They are generally cheaper than automated boilers.

  • Wood stove — Besides an open fire, this is the most basic form of a biomass heating unit. It is, however, much more efficient than an open fire and can be used to heat the whole home and provide hot water.

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How does a biomass boiler work?

solid fuel

A biomass boiler works by burning biological materials, such as wood or crops, just like our ancestors have done for thousands of years. We break down the process of how a biomass boiler turns these materials into heat below.

  • Biomass materials are fed (either automatically or by hand) into a combustion chamber where they are burned. 
  • This burning process produces hot gas and air.
  • The hot gas and air pass through a flue.
  • They then pass through a heat exchanger. This transfers the heat to the water used in the central heating system. Any excess heat is stored in a thermal tank.

If you have a manual hopper, you will need to refuel it every one to two days during the winter months and every two to three weeks during the summer.

Are biomass boilers cheaper to run?

Biomass boilers are typically cheaper to run than other types of boilers, especially if you buy in bulk. According to the Sustainable Energy Authority of Ireland (SEAI), the average cost of running a biomass boiler if you buy a bulk delivery of wood pellets is 5.96c per kWh.

You can see how the price of wood compares to other fuel types in the following table.

Fuel Cost (cents/kWh)
Wood pellets (bulk delivery) 5.96
Wood pellets (bagged) 7.21
Wood briquettes 9.33
Electricity 26.16
Natural gas 7.02
Gas oil 7.69
Kerosene 7.57

Source: SEAI

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How efficient are biomass boilers?

When properly installed and maintained, biomass boilers have an efficiency of around 80% to 90%. With an efficiency rating of 90%, around 10 cents are wasted for every euro spent on heating. With an efficiency rating of 80%, around 20 cents are wasted.

For comparison, electric boilers have an efficiency rating of 99 to 100% and gas boilers typically have a maximum efficiency rating of 93%.

How much does a biomass boiler cost?

For a domestic property, the cost of a biomass boiler generally ranges from €3,000 to €8,000. The cost of the biomass boiler depends on the following factors:

  • The type of biomass boiler
  • The fuel type
  • The storage size

Before buying a biomass boiler, you should request quotes from different companies to compare prices. In addition to the boiler itself, you should also get a quote for how much it will cost to deliver and install the biomass boiler.

How long does a biomass boiler last?

Biomass boilers are designed to last around 20 years. High-quality electric and gas boilers will typically last 15 to 25 years and an oil boil usually lasts 15 to 20 years.

Regular maintenance will help your biomass boiler last longer. You should get a standard boiler service every year (or every 2,500 running hours) and an extended service every two years. 

Pros & Cons: Are biomass boilers worth it?

Let’s have a look at some of the pros and cons of having a biomass boiler so that you can decide if they are worth it.

Pros of having a biomass boiler

  • Biomass boilers are considered renewable.
  • They are suitable for off-grid locations.
  • It’s a good way to use waste wood.
  • Biomass fuels are less susceptible to price increases than gas, oil and electricity.

Cons of having a biomass boiler

  • They need more space because they are often larger than fossil fuel boilers.
  • You will need storage space for the fuel.
  • There are increased maintenance requirements.
  • The burning process releases CO2, which contributes to climate change.
  • The upfront costs of buying the biomass boiler and having it installed are much higher than with oil, gas and electric boilers.

Still not sure if it’s worth getting a biomass boiler? Head to our guide on home heating systems to compare the different types and decide which is the best option for your home.

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