Treated woods present problems. Wood used in fencing, other outdoor structures or building work is often pressure treated with a range of preservatives such fungicides and pesticides, to prolong its life, and with other
chemicals such as fire retardants. Such treatments may have desirable functions while the wood is in use, such as resisting fungi, insects and fire but when trying to get the wood to decompose resistance to attack by fungi and insects ceases to be a
desirable property. The treatment is likely to contain a range of chemicals such as copper, chromium and arsenic that may be harmful to health and would contaminate other organic material if mixed with it when composting.
of treated wood is not recommended. It should not be put in the Council Green bin kerbside collection system or added to the Green waste at the local Recycling Centre. If treated wood and its residues e.g. sawdust , were placed in a green organics wheelie
bin, there is a risk that the harmful residue could contaminate a whole truck load of organic material and eventually enter the food chain, Similarly a residue surviving home composting could in theory contaminate plants grown using the compost.
Councils may permit householders to put small pieces of treated wood building material scraps, processed (either treated or machined) wood, off-cuts and residues such as sawdust in their “landfill” kerbside waste stream
while larger pieces should be taken to the Recycling Centre where there will probably be a separate bay for wood.
Community Wood Recycling website provides background information and details of the grading system operated by the Wood Recyclers
Association, which shows the end uses of different grades of wood. This information on grades is provided to encourage householders to separate their wood for disposal. (http://www.communitywoodrecycling.org.uk/learn-more/waste-wood/)
Grade A: “Clean” recycled wood – material produced from pallets and secondary manufacture etc and suitable for producing animal
bedding and mulches. Commercially recycled woodchip may be used as garden and landscaping mulch and it is added to green waste compost to adjust the C: N ratio.
Grade B: Industrial feedstock grade – including grade
A, but mixed with construction and demolition waste; this may be used to make panel board.
Grade C: Fuel grade – this is made from all of the above material plus that from municipal collections and civic
amenity sites and can be used for biomass fuel.
Grade D: Hazardous waste – this includes all grades of wood including treated material such as fencing and and requires disposal at special facilities.
Composting of treated wood waste
Commercial Composting of shredded waste wood requires a Standard Rules permit (SR 2010 number 14.) and treated wood must not to be used for any form of composting or land spreading, without a
Treated wood, including screened wood fines, must not be taken to composting sites after shredding. Compost produced using such materials does not meet PAS100 and the CQP and would be classified as a waste.
the Environment Agency would in principle allow it to be mixed with other allowed wastes to be biologically treated to produce a Compost Like Output (CLO) or Separated Organic Material (SOM) at sites with the relevant waste permit so if taking treated
wood waste or shreddings to the recycling centre please check the position.
An alternative to pressure treating wood, acetylation is chosen by some woodworkers, where available, as it results in
resistance to decay and insect damage as well as improved stability during moisture changes while apparently making it easier to machine and finish. Unlike pressure-treated wood, acetylated lumber does not contain any copper
In a paper Acetylated Wood The Science Behind the Material by Dr. Callum ( Renewable Materials School of the Environment and Natural Resources University of Wales. www.accoya.com/wp-content/uploads/2011/05/Acetylated-wood.pdf)
it states that “Due to its nature, it could be ground down to a form suitable for composting, or incinerated without release of toxic materials into the environment. A more appropriate strategy would be to develop a materials cascade approach.
Acetylated wood would be used as a feedstock for particleboard, MDF or other reconstituted wood products to make more dimensionally stable products”.
However this is more expensive than pressure treated wood and is not widely available,
it is included here for information purposesonly in case it does become more widely used. For the present it should be disposed off as treated wood.
In summary it is not permissible for treated wood to put in the
garden waste bin or green waste container at the Recycling centre as this could result in it being used for composting. Untreated wood may be beneficially spread directly to agricultural and non-agricultural land but only under an exemption or
a Standard Rules Permit