Christian M. 5 min read

Biomass Boilers

Over 80% of homes in Britain use a natural gas supply to power a traditional gas boiler that heats water and warms properties during the winter.

Although this system has worked well for decades, it is not sustainable. Natural gas is a fossil fuel that releases greenhouse gases into the atmosphere. Over 20% of the country’s carbon emissions come from heating homes, so a new solution is needed.

This article looks at Biomass boilers, a renewable alternative to gas boilers. Find out if you can benefit from the lower energy costs this technology can potentially provide.

What is Biomass?

Biomass is a renewable energy source released from burning organic (plant and animal) matter. Let’s briefly look at the simple example of wood.

A tree gets the energy it needs to grow from the sun. Leaves absorb sunlight using the chemical process of photosynthesis, converting solar energy, water and carbon dioxide into oxygen and organic biomass.

The larger a tree grows, the more biomass energy is stored in its leaves, trunk and roots.

To find out more about the chemical processes involved, here’s our complete guide to biomass.

What is a Biomass Boiler?

A biomass boiler uses combustion (i.e. burning) to extract biomass energy from wood pellets to heat water.

A biomass boiler has the same function as a traditional gas boiler, except instead of fossil fuels, it uses wood pellets. A biomass boiler is used to heat rooms and provides a source of hot water for properties.

How does a Biomass Boiler work?

Here’s a step-by-step process for how a biomass boiler works to heat a home:

A biomass boiler needs feeding with a supply of wood pellets; this is achieved with an automatic feed hopper, which uses gravity to push new wood pellets into the combustion chamber when needed.

The pellets are pushed into a combustion chamber, where they ignite at 600 degrees. The combustion process turns the biomass energy into heat energy, producing a flame and hot air.

The hot air is directed upwards into a heat exchanger that transfers the heat energy into the water, causing its temperature to rise.

The hot water is stored in a large cylinder and flows through the central heating system when required.

Are biomass boilers environmentally friendly?

Compared to traditional gas boilers, biomass boilers are cleaner as they have significantly lower carbon emissions when considering the entire life cycle of wood pellets.

Like natural gas, burning biomass also emits significant amounts of carbon dioxide. The key difference lies in their respective life cycles: natural gas takes millions of years to form underground, while wood grows within a couple of decades or less.

Wood is renewable at a human timescale, which means that as long as the timber used to make wood pellets is being replenished at the same rate as it’s being used, it’s a carbon-neutral process.

As a tree grows, it absorbs carbon from the atmosphere via photosynthesis until it is felled, and the sawdust is used to make wood pellets. When these get to your biomass boiler, the stored carbon is released back into the atmosphere, making the carbon balance equal to zero.

However, some experts have criticised the usage of wood pellets as the timber tends to be grown and processed into wood pellets abroad. These processes and their transport to the UK have an associated carbon footprint.

Also, there have been cases where natural forests have been cleared and replaced with forests for logging purposes, significantly affecting the local biodiversity, so sourcing the wood pellets is essential in understanding its environmental friendliness.

What are the different types of Biomass Boilers?

Biomass boilers generally refer to systems that burn plant matter to heat water. Biomass boilers come in many shapes and sizes, but here are a few of the main types:

Fully automated biomass boilers – The standard set-up used for woodchip combustion to heat the central heating system.

Combined heat and power biomass boilers – A more expensive set-up that generates both electricity and heat. Homes with combined heat and power boilers can benefit from the feed-in tariff or smart-export guarantee schemes.

Semi-automatic biomass boilers – Smaller boilers that work well in homes but need to be regularly topped up with woodchips.

An open fire – A traditional fireplace is also a type of biomass boiler as it burns wood to heat a room. Although quiet ascetic, a fireplace is not efficient and produces local air pollution.

Do you need to install a hot water cylinder?

Yes, unlike combi boilers, a biomass boiler can’t quickly turn off and on. A water cylinder stores the hot water it produces so it is ready when you turn on your shower.

If you don’t already have a hot water cylinder, this will need to be installed along with the biomass boiler.

Biomass Boilers and the Renewable Heat Incentive

Unfortunately, the Renewable Heat Incentive scheme closed on 31 March 2022.

The Renewable Heat Incentive scheme has been replaced by the Boiler Upgrade scheme. Through the boiler upgrade scheme, you can receive a grant of £5,000 off the purchase price of a biomass boiler. Find out more on the government’s website here.

How much does heating cost with a biomass boiler?

Since 2022, the wholesale price of natural gas has soared. The cost per kWh of energy from wood pellets is estimated to be £0.04 per kWh, making biomass boilers extremely competitive. There is an upfront cost, but this is significantly reduced by the £5,000 business energy grant available from the Boiler Upgrade Scheme.

At AquaSwitch, we help businesses find cheaper energy prices. Use our free price comparison service today:

Biomass Boiler vs Traditional Bolier

Here’s a quick list of the biggest pros and cons of replacing a traditional boiler with a biomass boiler:


  • Much better for the environment, renewable and carbon neutral (generally)
  • Cheaper to run than a gas boiler (at summer 2022 gas prices)
  • Low installation costs when supported by the boiler upgrade scheme
  • Can use other kinds of biomass, like Spent Ground Coffee pellets!


  • Biomass boilers need more space than a traditional boiler
  • It’s necessary to store large quantities of wood pellets in a dry space
  • You’ll have to arrange delivery of wood pellets regularly
  • A biomass boiler requires regular cleaning

Biomass Boiler vs Heat Pump

Heat pumps offer an alternative solution to heat properties without requiring a natural gas supply. A heat pump uses electricity to efficiently absorb heat outside a property to power a conventional central heating system.

Click out our ultimate guide to heat pumps.

Here’s a quick comparison of heat pumps and biomass boilers:

  • Efficiency – Heat pumps win out here with efficiency levels of 300% compared to just 60% efficiency with a biomass boiler.
  • Installation costs – The cost of installing both systems can be offset through the government’s boiler upgrade scheme, and the net price is similar for both.
  • Running costs – Heat pumps require an electricity supply. Since 2022 the cost of electricity has skyrocketed, making biomass boilers a cheaper alternative.
  • Lifespan – Considered similar, depending on which exact systems you adopt.


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