wood shredding recycling
Clean Class A shredded wood scrap is “perfectly suitable to produce high-quality wood-based panels,” says Jose Matas of Tomra.
Photo provided by Tomra Group.

Tomra matches its technology with wood recycling demand

Demand by particleboard makers for clean scrap wood has prompted Europe-based technology provider to assemble a team to serve this emerging market.

February 4, 2022

Tomra Recycling, a Germany-based business unit of the Norway-based Tomra Group, has built a dedicated team to match its sensor-based sorting technology with what it calls growing demand by makers of particleboard for consistently clean and sorted scrap wood material.

In an interview with the Recycling Today Media Group, Fabrizio Radice, Tomra Recycling’s Head of Global Sales and Marketing, is among three Tomra executives helping to describe the company’s progress toward its goal to offer automated scrap wood sorting systems.

Joining Radice for the interview are Jose Matas, Tomra’s segment manager for the wood market, and Ty Rhoad, Tomra’s regional sales director for the Americas.

Recycling Today Media Group (RTMG): What market or government circumstances are driving the demand for this advanced wood sorting technology?

Jose Matas (JM): Over the previous years, we have been observing an increasing demand for recycled wood that is driven by both the panel as well as the building and construction industries, both of which have recognized the enormous potential of recycled wood as a material. For instance, using recycled wood in the production process of particleboard (as one of the main application areas of recycled wood) comes with numerous benefits for the manufacturers.

First, they no longer rely on the availability of fresh wood, which is increasingly hard to get and, in addition, much more expensive than recycled wood. Second, fresh wood is generally more humid and requires more energy in the drying stage of the production process. Using scrap wood thus leads to greater energy savings and higher profitability for the particleboard board manufacturer.

Furthermore, particleboard manufacturers are looking to manufacture particleboard of superior quality. But to produce high-quality particleboard, the collected waste wood must be freed from contaminants, properly sorted and classified by wood type. Our sensor-based sorting units for wood applications offer a solution to this. Equipped with the latest technologies, they remove inert materials and metals in a first sorting step and further purify the pre-sorted materials (separating wood by type) in a second step. Particleboard manufacturers usually target a clean wood A fraction, since this is non-engineered and provides the necessary qualities and features to produce superior quality particleboard with a high level of salability.

From an environmental perspective, it can be stated that with the usage of wood-based panels in various applications, from the building industry to furniture production as well as using it as an alternative for more carbon-intensive materials, Europe could realize a reduction of CO2 emissions amounting to 300 million tons (15 to 20 percent). Consequently, the more wood-based panels are produced, preferably with recycled wood, the greater the environmental benefits.

Another driver of the increased demand for recycled wood comes from energy producers. They are using recycled wood that does not fulfill the quality requirements as woody biomass in energy production. Biomass proves to be a sustainable and economically viable alternative to energy production with finite fossil fuels. This development is increasingly supported by policies and subsidies granted by some governments, thus additionally driving the demand for recycled wood.

Ty Rhoad (TR): From a North American perspective, we see that the costs for lumber as a resource are at a historical high and that wood is still the material number one used in the construction industry. But whereas demand has not waivered, supply has. To date, most wood waste is burned and used for energy production, but although this approach diverts the materials from landfills, a lot of valuable material we could recycle and use to produce new materials is lost. Thus, it is time to turn to wood as a resource and retain its value by continuously using and reusing it.

RTMG: What markets are viable for the “clean” wood that is separated from the coated or “dirty” wood? What is the fate of the “B” grade product?

JM: Wood can be classified into four categories that are characterized by different purity levels. Their respective purity is the decisive factor that determines for which application and markets the materials can be used. In Europe, wood is classified into classes A, B, C and D.

Class A is non-engineered waste wood, thus the cleanest material class. The waste origin ranges from residues of sawmills, leftovers from forest cleaning to wood manufacturing and the packaging industry. Being the cleanest of all wood grades, it is perfectly suitable to produce high-quality wood-based panels, as well as animal bedding. Unlike other wood grades, wood A can be used in all applications, because it comes with the highest qualities.

Wood in the B class, on the other hand, is engineered and considered a “mixed grade” although not featuring halogenated coatings. It generally comes from business waste as well as from construction and demolition operations. Can be used also in the production of some types of wood-based panels, animal bedding, and landscaping.

The lower grades, C and D, are not suitable for the manufacturing of professional or consumer products. C is highly contaminated and originates from municipal collections or transfer stations. Thus, its main application lies in energy production in biomass plants.

Wood D, on the other hand, is hazardous waste coming from agricultural fencing, telegraph poles and railway sleepers. Due to its hazardous nature, it must be disposed of at special facilities with a particular license to accept and burn it.

TR: In North America, the clean wood fraction may also be used for particleboard manufacturing and to make synthetic silk (textiles). Wood B on the other hand is able to go into plasticized wood products. It cannot be burned in many states due to emissions from the glues. The challenge for A wood beyond use as fuel is a matter of creating a more reliable and profitable off-take market for it – and the opportunities for both recyclers and particleboard manufacturers are there, ready to be exploited.

RTMG: What types of optical technology are being deployed to make the separation?

FR: The separation of wood by material types (wood A vs. wood B or non-processed wood vs. processed wood) and the recovery of medium-density fiberboard (MDF) from waste wood require advanced technologies. Based on our industry expertise, we recommend deploying a combination of X-ray technology for a first sorting step followed by near infrared (NIR) and deep learning-based sorting systems for a further separation into wood classes. Integrating a combination of both systems allows for the recovery of single wood fractions and has proven to generate the highest quality results, enabling the materials to be further processed and recycled.

At Tomra, we offer both solutions. Our customers have been using our high throughput sorting solution X-Tract, which harnesses the power of dual-energy X-ray transmission (XRT) with high-resolution sensors, for ages. After the waste wood has been shredded, chipped and screened X-Tract removes the inert material (glass, stones, ceramics, etc.) and metals from the waste wood stream based on the material’s atomic density and regardless of the material’s thickness. Thanks to advanced technology and effective sorting by density and grain size, the product generated comes with a sufficiently high quality to be used in the standard chipboard manufacturing process.

Over the past few years, we have observed an increase in quality requirements and been approached by many customers who aim to use recycled wood of a much higher purity level in their production processes and for the manufacturing of high-quality chipboard. Since the increase in quality requirements entails the need to remove further materials, such as engineered wood composites as well as polymers, we had to find a new solution to serve the current as well as the future needs of the market and our customers. To do so we resorted to our wealth of expertise, our in-house team of industry experts, application engineers, and software developers collaborated to develop a new deep-learning-based application to sort wood chips by type. Gain is an add-on to our AutoSort units and enables the separation of diverse types of wood-based materials at higher purity levels, which is not possible using conventional NIR or X-ray technology only. Thanks to the most advanced and explicitly trained neural networks, combined with the latest sorting technology and sensors featured by AutoSort, recyclers can now separate wood A and wood B, as well as remove MDF from a mixed wood waste stream, giving them a competitive advantage [and] the necessary means to increase their overall yield and profitability.

RTMG: What type of technology is being used to conduct the sorting process? (Air jets? And if so, how are they configured?)

FR: The separation/ejection of the materials in both sorting steps (with X-Tract and the AutoSort used in combination with Gain) is carried out with high power valve blocks. Based on the sorting decision taken by the software, the valves generate a powerful and fast air blast to eject the material.

The ejection precision - and consequently the sorting quality - depends heavily on the correct choice of the valve block. We offer numerous sensor configurations to best meet our customers’ sorting requirements.

RTMG: To what extent is uniform piece/object size important when sorting, and how is this size uniformity best achieved? (A certain type of shredder?)

FR: The size of the material is an important factor contributing to sorting precision and recovery rates. The most common material size ranges between 15 to 60 millimeters (mm), or one-half inch to 2.5 inches for main applications. Fines sorting can be done between 5 to 15 mm (one-quarter to one-half inch) for more special applications.

In order to process the ideal sizes, raw waste wood must be shredded into sizes up to 100 mm (3.9 inches) in the first step, and big impurities (big metal pieces, stones) can be removed. In a second step, the material undergoes an additional shredding process and is reduced to grain sizes between 5 to 60 mm (one-quarter inch to 2.5 inches)– a size that is used to produce particleboard. Finally, disc screeners separate the materials into different target sizes depending on the application. Once these steps are taken, sensor-based sorting solutions conduct further purification.

RTMG: To what extent has the sorting technology reached an optimal throughput rate, or to what extent is improvement on that yet to come?

FR: At Tomra, our optimal throughput rates are constantly improving. We always try to have the highest throughput rates. Because we develop all our mechanics, software and sensors in-house, we have fast integration times. Thanks to our in-house teams we can optimize performance to make our customers’ sorting and recycling plants, which are situated around the globe, excel in performance.