The particleboard industry is the biggest user of recovered wood, although the energy sector is growing year by year. According to the latest EPF Annual Report, 32% of the raw wood used by the European particleboard manufacturing sector in 2014 came from recovered wood sources. This equates to just under six million tons per annum, which is a small fraction of the recovered wood available, so there is room for expansion.
Recovered wood is invariably chipped to make it easier to transport and store. Once chipped, the potential end-uses are limited to particleboard production, energy generation, animal bedding and mulches. Only particleboard production offers the possibility of further recycling.
Recycling particleboard into new particleboard can and is being done. Breakingup the particleboard generates dust that cannot be recycled and is normally burned to provide energy for the manufacturing process. Since some of the wood is ‘lost’ with each cycle, a particleboard cannot be recycled ad infinitum.
In addition, the average particle size must fall with each cycle and this will affect the physical and mechanical properties of the resultant particleboard.
Even so, particleboard manufacture is the best way to recycle wood, in my opinion. Having said that, I wonder if there is an even better alternative.
A couple of years ago a window replacement company asked the Ecole Supérieure du Bois (ESB) to explore what could be done with the windows which they removed. A couple of examples of what the students came up with are shown above.
One group used the entire cross-section of their window pieces to create a visually striking chair. Another group machined the window frames to ‘liberate’ the clean solid wood inside each piece to make another chair.
Accessing the clean wood inside recovered wood is the central idea of a European project called CaReWood in which I am currently involved. Instead of chipping, the idea is to try to maintain the dimensions of the recovered wood pieces as much as possible. One of the industrial partners in the project, M Sora dd of Slovenia, which makes high-quality windows, demonstrated the CaReWood principal by making a new window frame out of old ones, (see above right).
Reprocessed recovered wood in the form of solid wood has at least 10 times the value of the same wood in chip form and so this approach might make economic sense.
Recovered wood is vary variable; it is a mix of species, shapes, sizes, moisture contents, etc. Also, it is often associated with non-wood components such as glues and finishes. Not all pieces are suitable for the CaRewood process, for example jointed pieces that would be too costly to dismantle and, for those that are suitable, a lot of material in the form of sawdust, shavings and off-cuts will end up as particles for particleboard production and other traditional recycling uses.
In fact, having analysed a number of typical recovered wood pieces, we conclude that over 60% of the volume of the pieces that could be processed would be available to particleboard manufacturers.
Therefore, the CaReWood process should not have a great impact on the availability of wood for particleboard manufacture, but it should increase the profitability of recycling and so should encourage greater volumes to come onto the market.
