Most veneer mills don’t produce enough waste to warrant a pellet mill. They burn what residuals they create in a boiler for process heat and only run a surplus with a healthy order file. But a few softwood veneer manufacturers do produce enough waste that it makes sense for them to pelletize it, and there are good reasons for them to utilize waste in this manner. The price of natural gas is low, which makes gas-powered heat attractive. And boiler systems grow continually more efficient, requiring less biomass to operate. Manufacturers, therefore, have more surplus waste for which they must find a purpose or pay to landfill. Pelletizing the residuals is a proven and profitable option worth considering. It’s already being done successfully at veneer mills in Europe and numerous lumber mills in North America. However, before building a pellet plant, you should consider the challenges veneer waste presents.
Pellet Market 2021
Before we dig into specifics, it’s worth discussing the market and economics related to pellets. While pellet technologies have been around for decades, a shift to non-fossil energy production in Europe over the past two decades has created a stable export market for industrial fuel pellets. The export market is also set to grow in Asia, with Japan and South Korea investing in biomass power and requiring more fuel. Currently, the average price for industrial fuel pellets is $185.00 per ton domestically and $172.00 per ton for export. Retail price averages about $250.00 per ton in the United States.
The market for grill pellets in the U.S. has likewise grown recently. During the COVID-19 pandemic, the demand for grill pellets skyrocketed and has yet to abate. While the future for this market is uncertain, it does offer a lucrative option for hardwood processors. The average retail price for grill pellets in the U.S. is $0.90 per pound or $1,800.00 per ton. However, the cost to make the pellets is higher, as it involves batch processing, bagging operations, and strenuous inventory management.
Making Pellets from Veneer
As manufacturers have discovered as they’ve entered the pellet market, creating pellets is not as simple as it may seem. Wood waste is an abrasive, dirty, and acidic material that doesn’t flow well. And although the overall process of making pellets is consistent between manufacturers, the recipe for making them differs because each manufacturer has unique needs and feedstocks. Such it is with making pellets from veneer. Still, there’s plenty to glean from the industry as a whole about pellet feedstocks.
For example, dirty chips—those mixed with bark and dirt—do not produce high-quality pellets. Bark is broadly characterized by BTU values and ash percentages that make it less desirable in pellets. Dirty chips don’t help with operational costs, either. The dirt and sand increase maintenance because they inflict wear on bulk-handling and processing equipment. This isn’t to say pellet plants can’t turn a profit with dirty biomass. But it does increase production costs and lower the value of the end product.
There are advantages to strictly using clean material. Materials free of contaminants produce higher-quality pellets and reduce operational costs. It also opens additional markets for sales. Regulations for residential heating pellets (pellets for wood-burning appliances) are more stringent than for utility pellets. Residential pellets require a lower ash content, for example. In the U.S., they also cannot contain glues, resins, treated wood, construction waste, or pallets, among other materials. Plywood is listed explicitly among the prohibited items. While the amount of resin in plywood is small, it may likewise affect whether pellets containing plywood are suitable for industrial energy due to the pollutants they emit. We’re not overly concerned about this possible issue because the amount of glue is minute, but neither are we experts on air regulations.
Veneer manufacturers also need to consider segregating their waste if they process more than one species (as many do). To produce consistent pellets, they must separate and then uniformly blend feedstock from different species—at least hardwoods and softwoods. Segregating materials also gives them the option of blending at different rates to create unique products, such as a low-grade pellet for the utility market and a high-grade pellet for the domestic heating or grill market.
When it comes to handling veneer scraps for pellets (or any other purpose), there are a few points a veneer manufacturer should keep in mind. Before chipping the veneer, they must transport it with a belt or vibrating conveyor. This goes for slabs, cores, and other trimmings, as well. We’re sure you’re already aware of this, as you are that the conveyors should be constructed without catch points so the veneer doesn’t snag and form a bridge.
After the veneer has been chipped, belt conveyors, drag-chain (paddle) conveyors, and pneumatic conveyance systems can handle it. Out of these options, we recommend premium drag-chain conveyors, specifically SMART Conveyors™ from Biomass Engineering & Equipment, our sister company. We recommend these conveyors because of their robust performance and because BE&E designed them to comply with NFPA standards for explosion and fire safety.
We don’t recommend pneumatic conveyance systems for biomass wastes because they require far more horsepower than other transfer machinery. They also make a terrible mess when a hole forms, which is not uncommon given the abrasive nature of scrap wood. As for belt conveyors, they’re terrible at containing dust, which is a safety and maintenance issue. They also cannot convey material at steep angles and must run long spans to achieve any significant elevation change. Due to this, manufacturers commonly run them to bucket elevators, with which they elevate scraps to the chip bin. Bucket elevators are hardly trouble-free, either, as they often have trouble scooping chips and require vigilant maintenance to operate without problems.
Chipping also requires special attention because it presents one of the most significant challenges regarding veneer waste. When the veneer passes through a chipper or hog, long strips of material often escape along with the desired chip size. This usually happens when companies employ a chipper that crews set up improperly or which was designed for a material other than veneer. To avoid the creation of strips, the veneer processor needs a chipper designed for veneer. Veneer chippers have tighter tolerances than standard chippers and are less likely to pass oversized pieces.
Not only should veneer manufacturers looking to produce pellets employ a dedicated veneer chipper, but they should get one capable of producing microchips, small woodchips with lengths in the range of 0.23-0.39 in. (6-10mm). Pellet manufacturers prefer microchips because moisture within and between the chips varies less than in longer chips. As a result, the chips dry more consistently. Microchips have other advantages, too. They require less energy to grind and they provide a better distribution of particle sizes at the pellet mill. Better distribution results in denser pellets, which are less brittle and have higher BTU values.
Veneer Services’® FHI and VHI drum chippers can produce microchips with a minimum length of 0.23 in.
Storage and Infeed
Storing and reclaiming veneer chips takes particular thought, as well. Because veneer chips are flat and have a large surface area, they display poor flow characteristics. These characteristics mean scrap veneer bridges easily and does not flow through funnels. It also means screw-based, articulating reclaim systems have trouble. It’s not uncommon for reclaim arms to break as they try to pull apart the veneer chips. The pressure on the arm is immense due to the friction between chips. Long strips of veneer that may have made it past the chipper make this problem worse.
To avoid these problems, manufacturers do well to store veneer waste in horizontal silos and reclaim it with moving floors, wheel loaders, or a combination of the two. If they must store chips vertically, the silo should have relieving walls to keep the material from bridging. (A silo with relieving walls looks like an upside-down funnel with the base wider than the top.) In such systems, live-floor reclaim is preferable to an articulating screw.
After storage, a pellet plant that uses veneer as its feedstock is much the same as plants that utilize other materials: from storage, the material (if green) enters a dryer, after which it gets transferred to a feeder bin, which supplies the pellet mills. Are you considering other uses for your veneer waste? Our staff has decades of experience in the veneer and pellet industries as plant managers, operations managers, consultants, and equipment vendors. We know your material and what to do with it. Let us serve you as you seek to make your mill more profitable.