scope:

This guideline applies to facilities and appliances for the combustion of wood and wood-based panels including the resulting waste - particularly in the wood machining and processing industry - to the extent the wood fuel is free from wood preservatives and coating materials containing halogenated organic compounds and heavy metals. Facilities and appliances for the combustion of wood and wood-based panels likely to contain halogenated organic compounds and heavy metals as a result of treatment with wood preservatives or coating are covered by guideline VDI 3462 Part 5. The facility-specific emission measurement instructions are given in VDI 3462 Part 6.

As the emission limits to be met by such facilities vary significantly with the fuel quality and determine the design and equipment of the combustion and waste gas cleaning systems, measures for ensuring a uniform fuel quality are crucial to the combustion systems covered by this guideline.

In practice, it is, however, often difficult to tell whether the wood assortment to be burned meets the above criteria. The German Wood Waste Ordinance (AltholzV) only prescribes emission limits for scrap wood routed to reuse. For scrap wood-to-energy applications instead, it prescribes separation and sorting to segregate scrap wood treated with wood preservatives (category A IV) and scrap wood containing halogenated organic compounds as a result of coating (category A III) from untreated scrap wood or scrap wood with minor contaminant levels (A I and A II). The ordinance does, however, not mandate the separation of scrap wood coated with heavy metal-containing materials.

Until a few years ago, heavy metals (e. g. arsenic, lead, chromium, cadmium, cobalt) were frequently used as colour pigments in coating materials like paints, varnishes, films, papers, etc. These days, the greater part of the colour pigments employed are free from heavy metals. Except for the requirements of DIN 71-3 and -7, there are currently no standards regulating the allowable heavy metal concentrations of varnishes and paints used in wood applications. Compliance with the requirements of DIN 71 ensures that the heavy metal concentrations naturally present in wood will not be significantly increased through the residual heavy metals still contained in the paint or varnish coatings.

With coated scrap wood not originating from current production, by contrast, it is normally not possible to tell whether the varnish or paint coating is free from heavy metals.

For the requirements of the German Wood Waste Ordinance for wood routed to reuse and the requirements of DIN 71-3 and -7 for coating materials used in toys and modelling clay, please refer to Table 3 under Section 2.1.

Reference is made to the applicable laws, ordinances, administrative and other regulations applicable to the facilities covered by this guideline (see bibliography). Further processes and operations involved in wood machining and processing are described in Parts 1 to Part 3 of the VDI 3462 guideline series.

Unless expressly stated otherwise, all gas volumes indicated in this guideline relate to standard temperature and pressure conditions (273 K, 1013 hPa) after deduction of the water vapour content.