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Biomass Boilers

Biomass is the general term for natural or 'organic' fuel sources where the plant material which makes up the biomass fuel source, died relatively recently. This is what makes biomass different from fossil fuels such as coal, which are the remains of plants that lived millions of years ago. Biomass fuels can be either woody (eg wood chips) or non-woody (eg animal waste). Small-scale biomass systems usually take the form of boilers or stoves which use fuels including wood chips, wood pellets and logs.

The status of biomass as a renewable low carbon fuel means there is growing interest in the fuel.

The actual level of pollutants emitted in the flue gases depends on the biomass boiler design, the fuel characteristics and how the boiler is operated. The impact of emissions on the environment, in particular on the local environment is related to the dispersion of emissions, influenced by the height of the boiler exhaust stack.

The law relating to biomass boilers is complex with many areas of overlapping legislation. As the Borough of Dudley is a smoke control area the minimum requirements are that all boilers installed in the area must be exempted appliances under the Clean Air Act 1993 and the height of the chimney serving any biomass boiler capable of burning more than 45.4 kg an hour of fuel must be approved by the Local Authority. Further information on chimney heights can be found on the Chimney Height Approval.

Larger boilers may require a permit under the Environmental Permitting Regulations and depending upon the fuel used may fall within the requirements of the Waste Incineration Directive. The table below gives details on the respective legislative regimes.

Summary of pollution control legislation applicable to the operation of biomass boilers

 Fuel  Plant Size                                       Pollution Control Regime  Regulator

Biomass fuel arising

from natural sources

< 20 MWth

>50 MWth

20-50 MWth

Clean Air Act



Local Authority

Environment Agency

Local Authority


Waste or waste

derived biomass,

exempt from WID

<0.4-3 MWth and < 50 kg/hr

0.4 - 3 MWth and 50 - 1000 kg/hr

> 3 MWth and  >1000 kg/hr

> 50 MWth

Clean Air Act




Local Authority

Local Authority

Environment Agency

Environment Agency

Waste or waste

derived biomass

to which WID


< 3 MWth

> 3 MWth



Local Authority

Environment Agency


MW = megawatt, thermal.
LA-PPC = Local Authority Pollution Prevention and Control.
IPPC = Integrated Pollution Prevention and Control (Environment Agency).
WID = Waste Incineration Directive (Local Authority and Environment Agency)

Advice on Biomass Boilers

So if you are thinking of installing a biomass boiler we recommend that you contact the Council to obtain advice prior to making your purchase. This will help to ensure that you do not encounter any of the pitfalls of the law and that you have an appliance that is legal to use within Dudley.

Please use our online form to make your enquiry, or alternatively contact us using the details below.

In order to help with your enquiry please see the list below of the information we are likely to need in order to be able to offer you advice.

  • Thermal Capacity (MW)

  • Manufacturer

  • Fuel Type

  • Maximum rate of fuel consumption (kg/Hr)

  • Height of Stack (m)

  • Diameter of Stack (m)

  • Dimensions of buildings within 5 times the stack height

  • Discharge Velocity (ms-1)

  • Fuel feed system

Contact Details

  • Name Environmental Safety and Health
  • Address People Directorate, 3-5 St James's Road, Dudley, DY1 1HZ
  • Telephone 0300 555 2345