Wood residues arise at various stages during the life cycle from forest through wood use to final disposal, as shown in Table 1.1.
Potential wood residue contaminants identified in previous research have been categorised as shown in Tables 1.2 and 1.3. In the context of wood residue utilisation, water can be considered as a contaminant since high value uses, such as panel manufacture, require dry material. Residues which are wet cost more to transport per unit weight of wood, cost money to dry and are thus less valuable than dry material.
Table 1.1 Common sources and types of wood residues
Table 1.3 Typical assortments of wood residues and potential contaminants
Utilisation and disposal
The traditional methods for disposal of wood residues have been landfill, incineration and particleboard manufacture. However, the variety of uses is now quite wide, as can be seen from the list presented in Table 1.4. Of these, the most common uses appear to be for animal bedding, board manufacture, paper and board, composting and fuel wood while the disposal options are incineration and landfill.
Typical wood residue uses
Table 1.4 Typical wood residue uses
Animal bedding, cattle feed
Boardmills, paper and board mills, cement bonded boards & blocks
Composting, horticultural, mulch, soil products
Charcoal production, electricity generation, wood fuel / fire wood
Landfill, incineration
Liquid fuel and chemical production
New buildings, restoration, building forms
Oil mop-up
Pallets and pallet blocks
Playground underlayment
Remanufactured doors
Wood fibre/thermoplastic composite profiles for decking, windows and doors
Whether a particular residue is used or whether the only option is disposal to incineration or landfill, depends very much on the quality and quantity of the wood residue and the type and amount of contaminant present in the residue mix.
Supply issues also influence the likely success of reuse or recycling options. These include factors such as
continuity of supply in sufficient volumes
absence of contamination
marketability of products manufactured
no new disposal problems to be created
economically competitive.
Many of the wood residues collected for reuse or recycling are sorted into groups or types for which there can be several final end uses, examples of these uses are presented in Table 1.5.
Table 1.5 Recyclable timber products and their utilisation
As a means of improving communications between suppliers and buyers of wood residues a number of ‘trading post’ operations have emerged. These are in either printed or electronic format and work on the basis of providing details regarding volumes available / wanted and prices from which sellers and buyers are willing to start trading negotiations. Examples of these services include the American paper ‘Tennessee Materials Exchange Bulletin’ (Centre for Industrial Services, 1997), the UK Forestry Commission paper ‘Woodlots’ (Mason, 1997) and the UK web sites ‘Material Information Exchange’ (BRE, 1998) and The Environment Exchange.
