MDF is a real success story as shown by its rapid rise in production across the globe. It became the second most produced wood panel type in the world from 2012 until the bubble burst in 2022 (see figure 1).
Experts believe that the recent downward production trend will reverse soon, as it did after the financial crisis of 2008/9.
MDF is, of course, present in postconsumer, waste-wood (PCWW) streams. The phenomenal increase in MDF production started to have a noticeable effect on the make-up of the PCWW stream about 15 years ago, ie particleboard manufacturers had to adapt their production parameters when using PCWW.
Recycling a product involves the extraction of the different raw materials that make it up. Most of the non-wood materials, for example, knobs, hinges, nails, glues, laminates etc, in a product, like furniture, are closely associated with the wood, and so they are difficult to separate. Consequently, recycling wood products almost always has a chipping/ grinding step to liberate the wood from nonwood components.
This also has the advantage of reducing the bulk volume of the PCWW, which reduces storage and transport costs. Because PCWW is reduced to small pieces, the primary commercial recycling method for it is particleboard manufacture. The breaking-up of wood into small pieces inevitably produces dust that is difficult to recycle and so it is often burnt for energy recovery.
One advantage of chipped PCWW is that it tends to have a low moisture content compared to virgin wood. The average moisture content observed from all the recovered wood piles sampled in France by the EcoReFibre project is currently 19%.
This is low compared to the average moisture content of 23% observed by other researchers. The difference is probably explained by the fact that nearly half of the measurements were obtained from PCWW piles sampled in May-July, ie hot months. In contrast, samples collected in January had an average moisture content of 32%.
The round wood used to make particleboard tends to be small diameter, coming from thinnings and treetops. Such wood tends to contain a lot of sapwood, which has a high moisture content. For example, the moisture content of the sapwood of most softwoods is in excess of 100%. This is why particleboard manufacturers who use PCWW will need much less energy to dry the particles they require for their products.
CHALLENGES OF RECYCLED FIBREBOARD USE IN NEW PARTICLEBOARD PRODUCTION
The rapid and dramatic success of fibreboard, especially MDF, has increased the proportion of fibreboard in the PCWW stream. This is problematic for particleboard manufacturers because fibreboard breaks into non-ideal particles in terms of shape, surface roughness and internal fissures, as can be seen in figure 2.
Consequently, fibreboard particles create zones of weakness in particleboards. Adding more adhesive and/or pressing the particleboards to higher densities can ensure adequate mechanical properties, but both solutions increase production cost.
Therefore, more PCWW could be incorporated into particleboards if the fibreboard was removed before final chipping.
The EcoReFibre project is directly addressing this problem. The project is transferring previous research on particle sorting to make a sorting line that can remove most of the deleterious fibreboard particles at commercial production speeds.
There is surprisingly little data on PCWW streams. We do not know for sure how much is generated in Europe nor how much fibreboard is present in it.
The proportion of fibreboard present in the waste stream is dependent on: (1) The historical consumption of fibreboard and (2) The life-span of products containing fibreboard. The EcoReFibre project has collected data on these two factors so that it can model how much waste fibreboard should be present.
ECOREFIBRE MODEL
It is highly likely that a large part of fibreboard waste found in Europe will be derived from fibreboard panels made there. Some additional fibreboard, however, will be consumed via imported products, for example toys, craft products like boxes and frames, packaging and so on. Despite much effort, a reliable estimate of how much fibreboard from imported goods ends up in the PCWW stream has not been found.
By the time you read this, the model should be available for you to test (ecorefibre. eu). EcoReFibre’s waste generation model allows users to estimate the impact of imported goods by applying a factor to MDF production of the region, for example, the EU, France, etc. Therefore, you can conduct a sensitivity analysis by adjusting the amount of PCWW due to previously imported goods.
The model uses typical life-spans of different MDF-based products, which have been estimated via an on-line survey, using a “wisdom of the crowd” technique. The median life-spans of different product categories are shown in the table above.
These values are based on 188 replies. The end-use proportions (boxes with white background) are those determined by the European Panel Federation from their members in 2015. Consequently, the weighted average life-span of MDF made in 2015 is 12.4 years.
The same approach has been applied to the production years from 2002 to 2022 and from this we conclude that the average life of a product containing MDF of the last 20 years is about 12 years.
If it is assumed that 99% of the MDF manufactured in a given year becomes waste within 45 years, then the average life-span can be used to draw a waste conversion curve for that year’s production.
An example of such a curve is shown in figure 3 for panels made in 2015, with a starting point of 15%, which is the processing losses from the table (above). This curve predicts that 50% of 2015’s production had become waste by the end of 2023, ie eight years after it was produced.
If we apply a waste conversion curve to every year of production, then we can predict the total volume of MDF waste generated in any given year. Figure 4 shows that approximately 81 million m3 of MDF waste will be created across the globe during 2025. This volume is not far off the volume of new MDF made in the same year. This is a lot of waste that should be recycled.
Once the fibreboard has been separated from the PCWW stream it must be used. Consequently, other parts of the EcoReFibre project are developing technologies to extract useful fibres and fines from waste fibreboard particles and using these as substitutes for virgin wood fibres and fines. Some are being introduced into new particleboard and fibreboards, and others are being used to make high-performance, organic construction blocks. Additional information is available on the EcoReFibre website.
What is clear is that the EcoReFibre project is addressing a real challenge in the marketplace, and it will help the European wood-based panels sector to be even more circular than it is now.
ACKNOWLEDGEMENT
This article is a reworded version of a paper written by Dr Irle, Flore Lebreton and Christophe Belloncle (École Supérieure du Bois, Nantes, France) that was presented at the 13th European Wood-based Panel Symposium in October 2024, Hamburg.
The EcoRefibre project is funded by Horizon Europe (Call: HORIZON-CL4-2021- RESILIENCE-01).
