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MDF

Part composted MDF ready to be spread on farm land

stability, workability and low embodied energy

Made from wood fibre which is heavily compressed (in spite of it being called Medium Density Fibreboard) and bonded with some (or possibly no) formaldehyde adhesive, MDF is kind of similar to but at the other end of the density spectrum from cardboard. Imagine super, super, super compressed cardboard. The embodied energy is relatively low and the raw material is usually native hardwood which is not up to a standard to use as sawn timber.

It is quite economical to use in its basic 19mm and 25mm thicknesses with the common sheet size being 1.2 x 2.4 m. (not the same as the US 8 x 4 system which is now outdated). Larger sizes are available. One of its greatest qualities is its dimensional stability and its tendency to stay flat. Hence its use in kitchen cabinets etc. It is not waterproof (though water resistant grades are available) and if it does get wet it swells permanently. The stability means it is excellent for close tolerance furniture making, particularly for doors which tend not to wind in the way timber doors do.

It is easy to produce a good finish on MDF: it saws, planes, moulds and sands well. Faces take a good paint, lacquer, stain, wax or oil finish while edges require pre-treatment with a special filler (similar to cellulose sanding sealer – but thicker) to stabilize the cut fibres. In fact MDF can often be left in its natural state with no added finish. It tends to retain its surface finish well and is easy to clean with soap and water.

recycling MDF

Medium density fibreboard, which is widely used in furniture such as kitchen units has the potential to be recycled but it doesn’t seem to be happening much yet. Various companies such as EnviroFibre (in conjunction with TRADA) have successfully trialled processes for its recycling but most of it is now burnt or composted and then spread on farm land, supposedly to add fibre to the soil. However farmers have become somewhat wary of its use because of the damage which sometimes occurs to the land around the point where it is tipped prior to being spread.

Much of the problem with recycling is to do with removing coatings such as Formica from the MDF itself. In the case of composting, the coatings are simply crushed into small pieces (about a cm. or two in size) and these get spread on the land along with the wood particles. It is very difficult to get firm information on the safety aspects of composting MDF.

It seems likely that increasing land fill charges may eventually cause an increase in reuse of the fibre into new boards. Information on the current state of play is usually available at LetsRecycle.comFind a wood recycler near you.

MDF and health

There is HSE advice about working with MDF here. It is possible (but quite difficult) to obtain low and zero formaldehyde MDF in the UK such as Medite ZF. See also the Sustainable Design Association article on timber and timber based sheets

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