Waste Wood as a Biomass Fuel

In 2010, the UK’s annual arising of waste wood generated by households and businesses was estimated at 4.1 million tonnes.  About 2 million tonnes were diverted or recovered from the waste stream for recycling or energy recovery but the remainder continues to be sent to landfill, resulting in considerable environmental and economic costs.

Recycling companies currently pay thousands of pounds each year to dispose of their waste wood as well as the associated risk of fire hazards and accidents.  Between 2001 and 2013, there were on average more than 300 fires per year at waste and recycling plants around the UK.

Firstly, to clarify exactly what is waste wood?  Virgin timbers are not waste wood and not subject to special regulatory controls when burned as fuel, however where virgin timber is mixed with waste timber, or any other waste, the mixed load is classed as waste wood.

Non virgin timber such as off cuts, shavings, chippings and sawdust from the processing of non-virgin timbers (whether un-treated or treated) are classified as waste wood. Un-treated non-virgin waste wood, despite not having been treated with any chemicals, is waste wood. Treated non-virgin timber is any timber that has been treated (e.g. to enhance the performance of the original wood) or made into panel board of any sort is waste wood.

As classified by the Environment Agency: Grade A waste wood must be visibly ‘clean’ non-hazardous waste wood from the arboriculture sector, packaging waste, scrap pallets, packing cases, cable drums and off-cuts from the manufacture of untreated wood products. They would not accept as grade A, wood sorted from a mixed waste load delivered to, for example, a skip yard unless they are completely confident on how the wood is assessed and classified.

Grade B waste wood consists of non-hazardous waste wood from the production of wood-based panels; for example, chipboard and medium density fibreboard. Particle board manufacturing in the UK is subject to a gate-house protocol (PAS 104). In addition to visual inspection of incoming waste wood, sampling for heavy metals and halogenated compounds is carried out.

Grade C Waste wood consist of non-hazardous waste wood sourced mainly from construction and demolition activities, recycling centres and civic amenity sites. Grade C wood is used as a fuel in permitted co-incinerators but is not suitable for clean waste wood combustion plant. Due to the tight specifications and checks carried out by the board-manufacturing sector, visibly clean grade C waste wood may also go to wood-based panel manufacture.

Grade D waste wood can include any item of waste wood which has been treated, coated, painted or otherwise contaminated with any hazardous substance. This may include for example heavy metals and in particular, copper, chrome or arsenic (CCA), creosote, halogenated compound or metal pigment containing treatments, paints, coatings and preservatives.

When burning waste wood a special type of biomass boiler is required:

Grade   Type of boiler required for a process where a Part B permit is required

A            Industrial Biomass Boiler

B            Industrial Biomass Boiler WID (IED) Compliant may be required

C            Industrial Biomass Boiler WID (IED) Compliance will be required

D            Hazardous Waste Incinerator – Part A Permit required

It is possible to burn Grade A, or possibly Grade B, waste wood in a standard industrial biomass boiler (subject to any additional emissions controls to comply with permitting requirements) but Grade C (or possibly Grade B) may require what is known as a WID compliant boiler.

Although the WID regulations have now been amalgamated into the IED a boiler that complies with the requirements of the IED (to hold the combustion gases at a temperature of 850°C for a minimum of 2 seconds) it is generally referred to as a WID compliant boiler.

There are many advantages to recycling waste wood, such as the generation of free heat and hot water.  Tipping costs are also reduced and the Government Incentive (RHI) gets paid per kW heat  produced over 20 years.  Technical support is also available for companies to become a BSL fuel supplier (Biomass Suppliers List) providing a new income stream (must be supplied to boilers with the correct emission certificates).

By installing a biomass system, it can help to provide a 20 year additional income for a recycling business and can also reduce waste removal costs.  The heat produced can be a valuable source of heating to dry other products and another benefit of burning waste wood is you can produce electricity from ORC or CHP. Other positive factors include the reduction of accidents on the premises, the reduction of the risk of fire and the positive impact on the environment.

BGI are currently engaged with installing a biomass, drying and briquetting plant, from Eurobiomass, for a Recycling Centre in the North of England.

This is an ESCO funded 990 kW Biomass installation with drying facilities and briquetting plant housed in a building. The boiler being installed is capable of burning grade A & B waste wood since the site currently processes around 500 tonnes per week of wood, which is currently shredded and sent to landfill or sent for bedding processing to a third party, all at a significant cost.

The Recycling Centre plan to dry this material and manufacture briquettes, horse and cattle bedding and mulch from the process.  In order to achieve this, a 990 kW Eurobiomass Waste Wood Boiler with 2 Fliegl flat bed dryers with cyclonic dust suppression system are being installed. They will feed a hopper which in turn will feed a briquetting machine to produce the resulting briquettes.

This is just one type of solution available to UK Recycling Centres as many are realising that waste wood diverted from landfill becomes a resource and a source of income and energy for their businesses, for the future.

Author: Katrina Robson – Marketing Manager at Bio Global Industries Ltd (BGI)

For more information about this article, please visit the Bio Global Industries website.



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