Biomass boilers are very similar to conventional gas boilers that you will be familiar with, providing you with space heating and hot water for the entire home, but instead of using gas (or oil) to produce the heat, they combust sustainably sourced wood pellets.
Using wood in place of fossil fuels helps to prevent long-term climate change, since the carbon dioxide released during the combustion was actually absorbed while the tree was growing, so they are essentially carbon neutral.
Each year, approximately 8.5 million tonnes of wood goes into landfill in the UK; this waste wood could be used in either biomass boilers (if converted into the pellets) or burned in wood burning stoves. This would not only provide heat and hot water, but in doing so, it would also ease the pressure on landfill capacity.
A biomass boiler works in a very similar way to conventional boilers, combusting fuel to produce heat that is then used to heat water. Biomass boilers are normally substantially bigger than their fossil fuel-burning brothers though, for a number of reasons. Firstly since they are burning wood pellets as opposed to gas, the boiler needs to be larger to hold the larger volume of fuel.
In addition, you may wish to install an automatic feed hopper on your biomass boiler, which will require additional room. This hopper stores a large volume of the wood pellets that are then automatically fed into the boiler as required, meaning that the boiler needs to be refuelled very infrequently.
It is also a good idea to have a store of the wood pellets at your property so you can keep producing heat if for some reason there is an issue with your fuel supplier. Ideally this should be close to where the fuel is delivered to your home, to minimise the distance you have to carry it.
Most residential biomass boilers can also run on logs as well as the wood chips, so if these are in plentiful supply or if you can source them cheaply or even for free, it will dramatically reduce the operational running cost of your biomass boiler.
Every four weeks or so, the biomass boiler will need to be emptied of the ash. This can be put straight onto a compost heap to help fertilise the soil.
Biomass boilers are designed to work all year round; however you may choose to turn them off in the summer. They can be coupled with solar heating or an electric shower, providing you with your hot water for washing only, during the warmer summer months.
Biomass boilers measure up very favourably in terms of running costs vs. natural gas, heating oil and especially electricity. The numbers can all be seen in the table below.
Figures courtesy of Biomass Energy Centre
|Fuel Type||Price per Unit||kWh per unit||Pence per kWh|
|Wood Chips||£100 / tonne||3,500kWh / tonne||2.9p / kWh|
|Wood Pellets||£200 / tonne||4,800kWh / tonne||4.2p / kWh|
|Natural Gas||4.8p / kWh||1||4.8p / kWh|
|Heating oil||60p / litre||10kWh / litre||6.0p / kWh|
|Electricity||14.5p / kWh||1||13.4p / kWh|
A biomass boiler might simply be too big for your home, but smaller standalone wood burning stoves are also available, which are normally used to heat one room by burning logs or waste wood. These wood burning stoves can be fitted with a back boiler that uses the heat produced when the wood is combusted to heat water, that can then be used for either space heating elsewhere in the home or for hot water only.
Both standalone wood burning stoves and biomass boilers will need a vent, designed specifically for wood fuel appliances, with sufficient air movement for proper operation of the stove. Your existing chimney can be fitted with a lined flue, which is relatively inexpensive.
Under the Domestic Renewable Heat Incentive scheme, you will be eligible for payments towards the cost of installing the technology. These are quarterly, and over seven years, so you will still have to find the money to cover the upfront costs. How much funding you will receive depends on how energy efficient your home was before you installed your biomass boiler. You will start by having an EPC survey, and then payment rates are calculated by multiplying the ‘heat demand figure’ on your report by the current rate for biomass boilers. This means that some models will eventually be paid for fully by RHI payments, but many – especially top-end models – will not be covered completely. Find more information here.
It is really important when burning any type of hydrocarbon fuel (natural gas, coal, biomass) that you install a carbon monoxide detector in your home. In theory if all the fuel is 100% burned you produce heat, water and carbon dioxide, but in reality not all of the fuel burns. This means sometimes harmful gases like carbon monoxide can be emitted, which can be deadly. As long as you have a working carbon monoxide detector, you will be able to make full use of all the benefits a biomass boiler can bring.