Every day, sites across North America store millions of tons of raw and processed biomass used for a wide range of applications. These piles are several stories high and are constantly moving, piled by front loader or stacker conveyor, lifted with heavy equipment, and loaded for transport—all of which cause dust emissions.&nbsp; Whether kicked up by wind or normal activity, dust from stockpiles leaving the site line is heavily regulated and can be investigated by local, state or federal officials without the knowledge of the operator. Inspectors are searching for nearly invisible airborne particulate matter (PM) smaller than 10 micrometers (PM10), small enough to pass the body’s natural defenses and cause chronic breathing issues over time. Based on the government entity doing the monitoring, violations can range from corrective action to fines, or even a forced shutdown until an adequate remedy is applied. Sometimes the problems can build upon each other. A violation from a local U.S. EPA branch can trigger an Occupational Safety and Health Administration inspection to determine workplace safety violations.&nbsp; Violations are often initiated by complaints. If not properly addressed, they can also be followed by lawsuits. Regulations exist because airborne dust emissions have been deemed a serious public health issue. If litigants can prove air quality violations are caused by a specific substance originating from a defined location, then legal settlements and the erosion of public trust could force the closure of the operation. After a long-term risk and cost evaluation, environmental managers commonly include a dust control management plan as part of their environmental assessment. In these plans, environmental professionals often recommend using modern atomized mist cannon technology for stockpiles of all types. No other water-based technology has demonstrated the effectiveness that atomized mist delivers in controlling airborne emissions and keeping operations compliant.&nbsp; Causes of Airborne Stockpile Dust The key to controlling airborne dust is either prevention (surface suppression) or stopping it at the point of emission (airborne control). However, it helps to first define what is causing the dust emission in order to treat it properly. It will come as no surprise that the biggest cause of dust emissions for outdoor stockpiles is wind. Depending on the force of the wind, there is little an operator can do to keep the dust from becoming airborne, other than covering the piles or applying foam. Airborne suppression of outdoor emissions is typically accomplished using water. Field tests have shown that droplet sizes need to be roughly the same size as the airborne particulates due to the slipstream effect. This is the reason why atomized mist technology works, because the droplet sizes are 100-1,000 times smaller than those from hoses and sprinklers, making them far more effective against regulated dust emissions. Water propelled through hoses produces larger droplets because it depends on the water pressure to propel the droplets long distances. In contrast, an atomized misting cannon relies on a powerful fan to propel droplets, thus using far less water to offer complete coverage.&nbsp; Dust-Causing Activities Offloading raw and processed biomass into a storage area requires movement, which can cause dust even before the material reaches the pile. This is done by dumping, conveying with a stacking or tripper conveyor, or using equipment (earthmover, front loader, etc.). Operators have found that mobile misting cannons have worked well in controlling dust at the point of emission. When discharging material from a conveyor at height, a misting ring creates a curtain of mist around the discharge stream, capturing particulates and directing them toward the top of the pile. Disruption from equipment as material is moved, rotated or prepped for shipping is a cause of dust. In addition, the movement of tires and tracks on nonpaved surfaces during operations adds to the amount of dust. Around the storage area, managers who have implemented an oscillating central cannon around high-traffic areas have found that they maintain a dust-free environment when material is in constant rotation.&nbsp; Loading stored commodities involves disrupting piles, transporting material to hoppers and conveyors using large equipment, and distributing it in trucks, trains, barges, cargo ships, etc. Every point of this process produces airborne dust emissions. Along with misting rings, many operators have installed misting heads at hoppers and conveyor transfer points, sometimes with dosing capabilities to apply surfactants for hydrophobic materials.&nbsp; Best Practices For Stockpile Airborne Dust Control Offering both airborne and surface suppression, atomized mist technology can be fixed on a tower mount reaching as high as 30 feet (9 meters) and aimed directly at dust-causing activity. The equipment can also be mounted on a mobile carriage or skid, or delivered in a fully self-contained system on a mobile trailer with a water tank and genset. Large designs feature a specially designed barrel with a powerful 60 horsepower (HP) industrial fan in the back protected by a mesh cage, with a misting ring on the front. A booster pump sends pressurized water through the circular manifold, which is fitted with atomizing nozzles. The nozzles fracture the water into an engineered mist, throwing millions of tiny droplets in a cone-shaped plume. The largest cannons can throw mist up to 328 feet, with a coverage area of up to 280,000 square feet (26,000 square meters) when using the 359-degree oscillator.&nbsp;&nbsp; Operators who prefer the option of both pressurized water and atomized mist choose the versatile options that combine the power of an industrial fan, misting ring and heavy-duty barrel with the reach and force of a central high-pressure spray nozzle. The pressurized spray resists wind shear and even uses the force of the wind to further fragment and carry the droplets, enhancing its dust suppression capabilities. This is achieved without the need for the high water output associated with a hydrant-dependent hose or industrial sprinkler system. The three-stage center nozzle promotes efficient water usage, delivering a level of control unavailable in existing designs. Best Practices For Stockpile Surface Suppression&nbsp; Preventing the dust from becoming airborne in the first place is the preferred method of control. Only atomized mist technology offers both effective surface suppression and airborne control. Surface suppression protects the pile from shedding dust emissions. However, this is extremely difficult in outdoor operations where the material only spends a limited amount of time in depots or terminals before it is sold and transported. Figure 1 depicts some of the suppression methods.&nbsp; Dampening with water either from a hose, sprinkler or atomized misting cannon can wet the surface and lock the fine dusty material beneath. The goal is to make the material clump together and create a moist surface that prevents emissions. Hydrophobic natural fibers don’t clump, so they are difficult to treat with this method and may require a surfactant additive to ensure the water doesn’t merely bead on the surface and run off. Operators may find dampening labor intensive if they choose the hose method instead of an automated atomized misting cannon. Moreover, some commodities reduce in value with higher moisture levels, so controlling water volume is advantageous. Wind barriers that are natural or manmade can prevent wind from entering the storage area. Natural barriers can also capture much of the dust if dense and tall enough. This method is not always effective, but is an excellent supplementary measure when coupled with other methods. Covering material with tarps or biodegradable foam is generally only effective for short-term storage for a few hours or overnight. Tarps can rip, foam can deplete, and operators might find this method labor intensive for monitoring and maintenance. Enclosures are employed by many sites as a highly effective method. Construction, permits, space limitations, and maintenance may be cost prohibitive to some operations. Storage domes, covered storage depots, and large warehouses are all common for operations with set and predictable production capacities that are never exceeded. One of the obstacles to this method is that it concentrates dust emissions into the enclosure, creating a work environment that may not be compliant with OSHA standards. Often, this method is accompanied by indoor atomized mist cannons at known points of emission. &nbsp;&nbsp; Stockpiles and Wastewater Runoff Since outdoor stockpile surface suppression is only achieved with water, the issue of wastewater runoff can arise. This is highly regulated and tested for heavy metals and other toxic substances. Managers are often concerned with product loss, causing profits to literally run down the drain. The issue of standing water can also be a workplace hazard and machinery maintenance problem for some operations without proper runoff control that directs water toward an impound. Atomization introduces more droplets into the atmosphere using a fraction of the water volume. Because the mist is propelled by a fan rather than water pressure, the mid-sized cannon uses only about 25 gallons per minute (gpm) (94.5 liters per minute), as opposed to an industrial irrigation sprinkler system that can require up to 500 gpm pumped at 60-100 pound-force per square inch (4.1-6.9 bar) to adequately service the same area. Not only do the atomized droplets capture airborne particles, once they land, they also quench the storage piles, offering surface protection with far less runoff and product loss. Conclusion Stockpile management is a highly regulated and logistically complicated process. To remain compliant with dust regulations, operators find that they are constantly reacting to changing conditions, both with weather and volumes of material. This requires a versatile dust solution that offers both surface and airborne control, which can be achieved with atomized mist technology. Author: Mike Lewis&nbsp; Dust Control Specialist, BossTek

Dust control for biomass stockpiles can involve blending methods, including the use of both misting rings and cannons.

2023/08/Cont3-Dust-Control-Biomass_16909946035792_largethumb.jpg

2023/08/Cont3-Dust-Control-Biomass_16909946035792_thumb.jpg

2023/08/Cont3-Dust-Control-Biomass_16909946035792.jpg

Dust-causing activities as displayed in the image demonstrate the need for an oscillating cannon with wide-area coverage.

2023/08/Cont3-Dust-Control-Loading_16909946036217.jpg

2023/08/Cont3-Outdoor-Storage_16909946036618.jpg

Every day, sites across North America store millions of tons of raw and processed biomass used for a wide range of applications. These piles are several stories high and are constantly moving, piled by front loader or stacker conveyor, lifted with heavy equipment, and loaded for transport—all of which cause dust emissions. 

Best Practices for Biomass Stockpile Dust Control

Related Stories

Boiler and biomass industries align for large colocated energy event in 2026

Funding Forest Innovation: Leveraging the Wood Innovations Grant Program

A Black Pellet Resurgence and New Markets

SPOTLIGHT | CITGO: The True Cost of Grease Selection in Wood Pelleting

ENplus celebrates 15 years of setting the global standard for wood pellet quality

Upcoming Events

USIPA 2025 Conference

2026 International Biomass Conference & Expo

Best Practices for Biomass Stockpile Dust Control.css-7jxktu{position:absolute;bottom:0px;left:0px;right:0px;height:3px;border-radius:3px;background-color:var(--chakra-colors-brandBlack);}