The Evolving World of Wood Shredding
The intelligent reuse of wood is not a new phenomenon. As one of the world’s oldest materials, this sustainable resource has been recycled or repurposed by mankind for thousands of years, but the wood processing landscape has continued to change extensively.
In the U.S. and Canada, for example, preconsumer wood waste has been virtually eliminated, but the level of wood debris in municipal solid waste (MSW) and construction and demolition (C&D) streams show there is still room for improvement. There are at least 30 million metric tons of such recoverable material available in North America annually. Wood isn’t yet being best utilized in this respect, but awareness of the opportunity is growing.
In the United Kingdom, the Wood Recyclers Association has calculated that approximately 2.8 million metric tons, or 60 percent, of the country’s waste wood is being recycled. But according to the Health and Safety Executive, that figure, along with the number of companies involved, is expected to rise. In Austria, where forestry and wood processing industries are important elements of the country’s economy, biomass is widely regarded as the most important renewable energy source, with Austria’s ratio for biomass production and utilization above average.
A lack of uniformity surrounding global analysis methods means that it’s difficult to paint a conclusive picture of wood recovery worldwide. However, wood is increasingly being acknowledged as a valuable resource that needs to be comprehensively salvaged and processed. In some parts of the world, this acknowledgement is so great, that shredding capacity actually exceeds the amount that biomass plants can take.
Market Forces Shape Plant Design
It may sound odd that extraneous forces should influence a plant’s design at an operational level, but the careful selection of a plant’s component parts can have a significant impact on a wood processor’s bottom line. The design of a plant and the procurement of specific technology can be a very strategic move.
It is still possible to make money from wood processing for biomass, even in countries where capacity is high. In many areas, however, gate fees are increasing, and the commodity value of the processed material has dropped. In order to achieve maximum commercial viability from wood shredding, plants must be designed for easy operation, with low running costs and maintenance simplicity in mind. This will minimize biomass production costs per ton. If the wood can be shredded without the need for post treatment, such as a screen, this further streamlines the process, not to mention the need for additional capital expenditure.
Considerations Beyond Capacity
While wood processors have long focused on the impact that a shredder’s throughputs and capacity can have on their profitability, the gradual maturity of the market means performance is now being analysed slightly differently. For instance, particle homogeneity is becoming increasingly important. The biomass market demands a fuel manufactured to a defined specification, for maximum energy value. If a shredder produces fines (dust-like, nonspecification material) as low as 5 percent, it’s possible to yield up to 20 percent more saleable biomass material per ton than traditional machines on the market, often without the need for additional screening systems. The shredder becomes an even greater revenue-generating asset, while the disposal costs associated with these unwanted outputs is also reduced.
Such cost-driven criteria are extremely important when designing new wood processing plants, and when replacing outdated shredding technology on existing sites. Some operators may even decide to redesign their plant purely for these fiscal reasons, recognizing that low whole-life running costs can reap significant financial and operational efficiencies in the longer term.
Need for Flexibility
It is perhaps because of these market forces that there has been a notable increase in the demand for flexible waste shredders. Some manufacturers have long claimed to engineer “universal” machines capable of handling varied waste streams, but investment in a one-size-fits-all solution has often meant the need for operators to compromise on results.
Technological innovation, however, has brought about the ability to design truly flexible shredding systems that can proficiently handle wood before being reconfigured, in two hours or less, to process other, very different waste streams. Such versatility may prove crucial for some operators during periods of market value fluctuation, not to mention the evolving nature of the waste landscape on the whole. Few organizations now stand still in terms of the wastes they produce, which means recycling and recovery firms need to adapt.
Moving Away From Tradition
In many parts of Europe, wood processors have long operated diesel-driven mobile shredders, with often questionable noise, pollution and energy efficiency statistics. Some would argue this is because it has been the only technology available, while others would suggest it has simply been regarded as the norm—if it’s what a competitor has traditionally used, they should, too.
In truth, some firms don’t need a mobile machine, as it never moves from a sole location. With static wood shredding technology as advanced as it now is, there’s no need to buy mobile equipment if it’s always going to be in one place. In plants where mobility is important, perhaps due to safety or insurance reasons, it’s still important to assess what is available in the marketplace and what best fits a processor’s needs. At the very minimum, the shredder should be supplied on tracks, with an in-built magnet and conveyor, for convenience. Electric-driven, energy-efficient options are available, which save on power consumption while minimizing the environmental impact on staff and neighboring communities. And shredders with a quiet operation, ideally below 80 decibels, should be prioritized, to protect the hearing and well-being of staff.
The wood shredding market has been blighted with a number of devastating fires that have put personnel, the business and the wider community at grave risk. In the U.K., for example, the Health and Safety Executive is urging processors to think carefully about plant design to ensure these risks are mitigated as much as possible.
Thorough cleansing regimes are imperative to minimize the level of dust on-site, and the installation of sprinkling systems throughout a plant can help combat a fire if combustible material ignites. A number of shredder manufacturers have also acknowledged the support that they can provide to control the danger.
Operators should think carefully about the machinery they procure to shred their wood. In-built fire suppression systems throughout a shredder’s hopper, cutting chamber and discharge conveyor can help to prevent hot, glowing or lit material from exiting the machine, thus reducing the risk of fire. That is consideration No. 1. A slow-speed shredder, which operates with high torque to ensure throughputs aren’t compromised, is consideration No. 2. With this technology, dust levels are significantly minimized, and the potential for a spark is also reduced, which drastically lessens the risk of fire when compared to other machines.
Reduced levels of airborne dust would also protect the health of personnel continually exposed to the operational conditions of wood shredding.
Of course, every wood shredding scenario is different, and the considerations an operator must make can soon feel quite complex. That said, plant design has evolved from simply thinking about getting from point A to point B. It remains crucial to manufacture a high-quality biomass product, as cost effectively as possible, but because technology has evolved, one should think beyond tradition, and look at ways to improve energy efficiency, plant safety, personnel well-being and environmental impact. Do this well, and there will be multiple opportunities to improve the bottom line along the way.
Author: Peter Streinik
Head of Business Unit Waste, UNTHA
+43 6244 7016 65