Cascading Wood Towards the Circular Economy

cascading wood circular economy

Trees, the source of all wood, are a perfect example of the circularity in nature that the circular economy tries to model: a tree grows out of the nutrients found in the soil, and it returns these nutrients back into the soil once it reaches the end of its life, fueling the growth of the next generation of trees.

Wood: circular in nature, but not in the economy

Though trees are circular within nature, the wood garnered from them for our consumption is still far from circular within our economy. The demand for wood has far surpassed the earth’s natural, sustainable wood supply, and the wood that is being used often does not make it back into the start of the value chain. This is largely due to the fact that, unlike many other materials, wood cannot be melted down and reshaped into a new product. Wood can never be renewed at the same or higher quality level – its value is continually downgraded throughout its life cycle. As a result, much of the wood ends up incinerated or in landfills.

As the physical makeup of wood cannot be altered to heighten its prospects of recycling and upcycling, the next best solution is to take full advantage of each grade stage of wood by cascading. Three students from TUDelft, Manuella Borgers, Niki Versteeg and Marco Vogelzang, developed six stages through which wood should be cascaded in order to get the most value out of the wood as possible.

This blog summarizes the six stages outlined in their paper.

The six steps of cascading wood through the circular economy.
The wood cascades down through each step, extracting maximum value throughout the process.

Stage 1: Raw Materials

Wood begins its journey within the circular economy at harvestation as a raw material.

There are three main sources from which wood is harvested:

  1. Production forests. These are forests that have been planted specifically for wood harvesting.
  2. Production in cities. This is the wood that is collected as a result of the maintenance pruning of trees in parks and streets.
  3. Harvesting wood from natural forests. This wood is derived from harvesting some portions of recreational forests and nature reserves.

Ideally, wood should be sourced as much as possible from production forests and cities in order to leave the earth’s vital natural forests largely untouched.

Stage 2: High-Grade Boards

Wood as a raw material must now be processed into a workable resource: wooden boards.

In this beginning stage the raw material should be processed minimally in order to retain as much of its original strength and properties as possible. This is important for retaining the boards within this grade stage for as long as possible, as this is the stage in which the wood is at its highest quality and value.

The by-product of this manufacture is sawdust. There are several options for this sawdust: it can be used in the next stage in the production of fibreboards, or it can be incinerated on-site to fuel the wood drying process of board production.

At these boards’ end of life, the wood is sorted into three quality grades:

  • A: untreated wood;
  • B: painted or glued wood;
  • C: impregnated wood.

Wood from class A and B are of a high enough quality to be recycled, often being cut into chips which can be used in the production of particleboards at the next stage. Wood from class C goes directly to incineration for production of renewable energy.

Stage 3: Low-Grade Fibreboards and Particleboards

In this stage, lower-grade boards are made out of the sawdust and woodchips generated during the production or recycling of the wood boards in the previous stage.

It is difficult and costly to reuse or recycle these boards, as they are made of lower-grade wood. Hence, their next step is to be downcycled into paper.

Stage 4: Paper

The fibres in the fibreboards and particles boards are given a new life as paper.

The paper produced at this stage can also be recycled at this level, before its fibres are yet again downcycled as a fuel for energy production.

Stage 5: Energy Generation

Finally, the wood biomass gives its last life as fuel for energy generation.

Currently, there is an expected 319% increase in the demand for wood used for energy generation. This demand surpasses the supply of wood from used products, which means that freshly harvested, high quality Stage 1-grade wood is needed to fulfil this demand. At this rate, circularity will not be reached. It is these three students’ vision that in the future only wood that has been downcycled will be allowed to be used for the generation of energy.

Stage 6: Regeneration

Just like in nature, the wood comes full circle as the ashes and CO2 generated by the incineration in the previous stage are captured and dedicated towards the growth of new trees.

By growing new trees, we are doing something that cannot be done with other materials: we are putting the raw material back into the earth, to support a regenerative and sustainable material source.  

Through cascading wood through all of these six stages, we make use of it at every stage, and thus we retain the maximum value possible from the wood throughout its entire life – value that would otherwise be lost if the wood boards were dropped immediately from Stage 2 down into energy generation at Stage 5. This makes it a good model to follow for the circularization of the wood industry.

Want to get the most value out of wood?

We at MaterialTrader help make it possible for wood to be cascaded down towards a second or even third life, by facilitating the trade of secondary wood and timber products on our materials marketplace. If you are looking to buy or sell wood, trade it on our platform, and help us forward a circular economy of wood.

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