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Don't risk your RHI by using waste wood in your boiler

There have been questions raised regarding the use of waste wood in boilers meant for virgin wood fuels. The rules laid out by OFGEM are very clear. Waste wood of any kind whatsoever MUST NOT be used in boilers that have been accredited using virgin wood.

 

Wood Chip Grades

 

 

Issues with Waste Recycled Fuel

There are some very serious consequences of using waste fuel in a non-compliant and unsuitable boiler. This list below is what your waste supplier will not tell you about;

  • If your RHI application was for virgin timber you will be breeching the terms for the RHI and therefore you will be fined and may be asked to repay your RHI payments to date.
  • Your annual RHI declaration asks whether you have made any changes to fuel or your system. If you say ‘No’ on your response, then this will be a breach of contract and classed as fraud. Your RHI application could be terminated.
  • The use of any kind of waste material as a fuel (including grade A clean recycle wood waste) means you must have an Environmental Permit to do so.
  • Simply obtaining an Environmental Permit does not mean that you can burn waste, it only stipulates the permitted levels of air born contaminants. If the airborne contaminants cannot be abated through the use of filters, then you will not be able to operate the machine. Recycled waste (unlike virgin wood) generates higher levels of NOx and Sox.
  • To abate increased levels of particulates generated by using waste wood, a cyclone filter or a mesh filter will be required.  Mesh filters can cost £12,000 plus per boiler for 199kW machine and c. £60,000 for a 1MW machine.
  • A CEMs may also be required (Continuous Emissions Monitoring System) which test the emissions to show compliance and automatically shut down the boiler should it go over peak limits of emissions.
  • Once an EP has been obtained, and any necessary mesh filters, cyclone filters and CEMs have been installed, you must re-apply to OFGEM for reaccreditation. You may not be accepted on the RHI scheme or if accepted, you may be accredited at a lower tariff.
  • I you are randomly audited by OFGEM you will need to have evidence of your total virgin wood fuel purchases that corresponds with the kWh generated on your meter. Historical invoices, showing BSL numbers and quantities supplied will be required. Having a small pile of virgin timber on site does not qualify as ‘evidence’ as it is an insufficient audit trial for the wood being used.
  • Your boiler warranty will be invalid and increased damage, wear and tear will occur resulting in more maintenance and increased down time.

 

FURTHER READING

Virgin Wood

Virgin wood originates only from virgin ‘in the round’ timber, usually derived from the following species (douglas fir, pine, larch) commonly known as SPF. On occasions Poplar, larch, Cherry and other woods are included. It is obtained in accordance with the requirements of BS EN 14961 from traceable, sustainable managed woodland; and is often certifide by accreditation bodies such Woodsure Ltd.  To be eligible for the Governments RHI (Renewable Heat Incentive payments) it has to be registered under the Biomass Fuels Suppliers List. Some wood fuel suppliers (such as Chip Chip Ltd) also choose to have their products additionally and independently tested and be inspected and analysed for specification consistency every 4 weeks by Alfred H Knight or similar; and shall be monitored under an environmental management system certified with Green Dragon to Level 3 or ISO 14001 equivalent; supplied by Chip Chip Limited;

 

Waste Wood

As soon as it is called a “waste fuel” then it needs a permit.  There is however a limit, and also some exemptions.

Plants burning less than 50kg/hr do not need permits.  This is about 135kW (chip) and 200kW (pellet).  There are also references to 0.4MW thermal input, but this is for a different section and is in addition to the 135/200kW limit (from section 5.1).

The key is in defining waste.  The Environmental Agency have release a briefing document (V1 September 2014) to clarify this.  In outline:

-          Virgin timbers are not waste

-          Non-virgin timber offcuts, shavings, chippings, sawdust are waste

-          Non-treated (or un-treated) non-virgin waste wood is waste.  This section specifically includes panel board of any sort.

-          Treated non virgin timber is waste

 

Virgin timber is timber from:

-          whole trees and the woody parts of trees including branches and bark derived from forestry works, woodland management, tree surgery and other similar operations (it does not include clippings or trimmings that consist primarily of foliage2);

-          virgin wood processing (e.g. wood offcuts, shavings or sawdust from sawmills) or timber product manufacture dealing in virgin timber.

 

The Environmental Briefing Document goes states:

“The information so far provided on the treatments applied to waste wood is insufficient to give us confidence that all Grade A ‘clean’ timber is clean enough to be used for a number of the uses highlighted above and we therefore continue to classify it as 'use of waste'. Further, the Environment Agency's experience to date is such that we do not have the confidence that general procedures for segregation of waste wood are sufficiently robust for some end uses. Use of waste wood must therefore be in accordance with a relevant exemption or permit.”

Clean untreated waste wood is highly likely to give off higher levels of increased NOx and Sox. This is because there will almost always be nails, screws, plastics, paint, stenciling, treatments, etc.  In that case the NOx and SOx are likely to be increased over virgin.

The requirement for the filter is driven by stringent limits on PM emissions.  RHI requires just a single test which demonstrates emissions over a limited period.  EPR permit requires a guarantee from the filter manufacturer, otherwise CEMs will be required (Continuous Emissions Monitoring System). They also need proving with alarm for the dust filtration equipment, which cannot generally be fitted to the standard-fit abatement technologies.

It is also important to point out that burning wood would be a section 1.1 or a section 5.1 activity (chapters 1 and 5 of the Environmental Permitting Regulations, EPR).  Certain fuels also come under section 13/13A.  EPR covers a range of activities.  Even if a permit for processing waste is granted, this would be a different activity (i.e. section 6.6), and would therefore require a different permit or at the very least a variation to a permit before a biomass boiler can operate on waste fuel.

If a permit (issued under EPR for the correct activity) then there is no need for an RHI emissions certificate (RHI-ec).  The permit takes precedence over the RHI-ec (it is slightly more stringent in some respects slightly more lenient in others, but is nonetheless more robust and onerous overall).

Requirement for CEMs varies, most Binder GmbH boilers have on-board controls that are acceptable and sufficient CEMs for a well-controlled process.  Other boiler brands this may not be the case.

 

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Waste Wood Cover