From Risk to Benefit

Market development for wood pellets in recent years has been strong, but the increased demand for raw material and larger storage capacities has led to new, challenging hotspots.
By Holger Streetz | May 31, 2019

Market development for wood pellets in recent years has been strong, but the increased demand for raw material and larger storage capacities has led to new, challenging hotspots. With more piles, the risk of self-ignition escalates. There is a solution to the risk, however, and it comes with additional, not-so-obvious benefits.

It has become very difficult to obtain enough feedstock at reasonable transportation costs. Especially with sawdust, the low density of bulk raw material leads to high tons-per-square-foot storage costs. Even more problematic is the fact that woody raw material for pellets is a reactive fuel, and therefore, self-ignition of bulk material is a constant risk. Once the oxidation shifts from biological to chemical and the heat cannot dissipate due to the size of the pile, woody biomass self-ignites. Self-ignition depends on different factors, such as pile size, time of turnover and moisture. A pile on fire is very difficult to extinguish and can cause long downtimes and supply shortcomings.

To reduce self-ignition risk, a solution has to: be airtight and weather resistant, avoid piling of material, be easy to load and unload, and be financially reasonable. Baling, a densification process of loose material into easy-to-handle shapes such as blocks or cylinders, is one possible solution. A bale improves manageability and reduces transportation costs, and importantly, minimizes self-ignition risk due to air tightness. The compression ratio depends on the material. Bark and wood chips, for example, are dense and chunky, so baling can only improve transportation by some 20%. Sawdust can be compressed up to a ratio of 1-to-2, which means baling gives the company the options of either sourcing cheaper from existing suppliers, or increasing the sourcing radius for a higher variety of raw material, which ultimately leads to a more homogeneous feed that smoothens the pelleting process. It also adds the potential to expand production.

The floor usage per square foot of compressed material is higher, which is important for plants with scarce storage areas. A 40-foot-high pile of sawdust with a diameter of 170 feet can be reduced to an effective storage floor of approximately 40 feet by 20 feet. However, the compressed material needs debaling, too. A debaler, equipped with automated pallet handling and dust suction system, reduces work to a minimum.

Besides improving transportability and storage efficiency, baling raw material can have an additional positive effect by creating sellable byproducts. Bark is usually a poor feedstock because it contains many impurities such as sand or metal, and therefore increases wear on the equipment (especially the roller shells) and maintenance (cleaning of magnets). Due to the higher ash content, only a few bark varieties can be used for PFI or ENplus residential heating pellets, and not every dryer is able to run on bark. Bark is an essential ingredient of bituminous peat, turf and mulch, however, and therefore a valuable raw material. Bark is also used as a decorative ground cover and can reach prices of $15 per cubic foot, or $405 per cubic yard.

In short, a baling system might swiftly pay off for companies that deal with long-distance transportation of loose raw material, are able to sell byproducts to nearby turf producers, or have inadequate storage capabilities. 

Author: Holger Streetz
International Operations Manager, Bathan AG