As the wood pellet industry faces tightening emissions standards and expands to include advanced pellets and unconventional feedstocks like bagasse, emissions control is becoming more nuanced and more operationally critical. Facilities must balance performance, compliance and reliability while managing complex air streams, and engaging the right emissions control engineering firm is critical to enabling producers to accomplish all of the above.&nbsp; Jaymie Deemer, president of NESTEC, says the industry’s challenge isn’t just adding controls, but ensuring systems are sized, operated and maintained in a way that keeps plants comfortably within permit limits and away from the edge of compliance, while supporting reliability and uptime.Emissions Control inToday’s Pellet Plants Founded in 2005, NESTEC has a breadth of experience supporting both conventional wood pellet and black pellet production, as well as bioenergy and biofuel facilities and other industries. The company designs and services systems such as wet electrostatic precipitators (wet ESPs), regenerative thermal oxidizers (RTOs) and catalytic oxidizers to control particulate matter (PM), volatile organic compounds (VOCs), carbon monoxide (CO) and hazardous air pollutants (HAPs) generated during drying and thermal processing. In addition to equipment design and supply, NESTEC provides troubleshooting, on-site support, technical support and upgrades to help facilities achieve and maintain compliance and system performance. For example, the company was engaged by wood pellet producer Georgia Biomass to reduce VOCs and HAPs to meet EPA Title V permit limits while optimizing operational efficiency, and NESTEC was able to successfully resolve the facility’s compliance issues. The company’s ongoing work reflects the differing emissions profiles and operating conditions associated with traditional white pellet production and the reduced-oxygen, higher-temperature processes used to produce black pellets. According to Deemer, emissions control is no longer simply a permitting requirement—it is a core operational system that affects uptime, safety and long-term plant performance.An Eye on Emissions In most pellet facilities, the greatest emissions control focus centers on the dryer island—the main generator of PM and organic emissions. “The wood dryer island has the most emission control equipment, comprised of a wet ESP to control PM and a thermal oxidizer to control VOCs, CO and HAPs,” Deemer explains. “The wet ESP also protects the downstream RTO from plugging and reduces visible emissions.” Other process points require attention as well, particularly post-drying operations. “The dry hammermill and pellet cooler emissions typically have a wet scrubber or baghouse PM control device, followed by an RCO or RTO for VOC and organic HAPs control,” he says. When pellet facilities run into compliance headaches, it’s not always because any single piece of equipment is failing. Deemer says the bigger hurdle is often reconciling emissions across the entire site, especially for facilities permitted as synthetic minor sources. “The biggest challenge is typically making the emission inventory line up for the entire site,” he says. “Most pellet mills are permitted as a synthetic minor source (SMS), which has facility wide limits on VOC, CO, HAPs, PM, NOx, etc.” For larger mills operating under SMS limits rather than than a Title V major source, the balancing act can tighten quickly. “If the pellet facility is large and permitted as an SMS and not a Title V major source, then it can be challenging to make all of the various plant emission sources balance out with achievable concentrations for each of the pollutants,” Deemer says. Some of the industry’s most common problems emerge during startup or production ramp-up, when plants discover that actual operating conditions don’t match the original basis of design. “There have been issues in the industry over the years with heat energy and dryer systems requiring a higher exhaust volume to the emission control system than the original design conditions,” Deemer says.&nbsp; He lists several drivers: “This can be caused by an inefficient dryer design, dryer furnish moisture content, moisture content of the upstream fuel at the furnace, dryer recycle rates, and even operations pushing the system harder than design, for additional production.” When that happens, even well-selected technologies can struggle if they’re too small for the job. “These issues can create issues with the downstream emission control equipment being undersized, including the RTO exhaust fan horsepower,” he says. Deemer adds that performance can also hinge on human factors—e.g., training and experience. “Other challenges are related to new operators learning the emission control technologies and the ongoing maintenance requirements to achieve high performance.”A Well-Performing Emissions Control System High-performing systems share a few consistent traits, according to Deemer. These include: “High equipment uptime and limited maintenance requirements, comfortably achieving the removal and destruction efficiencies of the various pollutants, and efficient electrical power, natural gas and chemical consumption,” he says. He also points back to the wet ESP’s role upstream of oxidizers. “With the dryer system, the wet ESP plays an important role in protecting the downstream RTO from plugging and alkaline attack of the ceramic heat recovery media,” Deemer says. And while wet ESPs are a well-known technology, performance still hinges on details that can be underestimated. “The power input to the electrostatic fields, especially the voltage, is paramount for wet ESP performance,” he says. Deemer emphasizes that there are specific design considerations that can help maintain emissions performance in the long-term, such as designing with adequate safety factors and avoiding undersized equipment. “Specifying the correct gas volume should include a safety factor of at least 10 percent,” he says. He also recommends targeting upstream particulate control in a way that protects the oxidizer over the long haul. “Include a PM control device emission target that ensures reliable operation of the downstream oxidizer and long ceramic heat recovery media life,” Deemer says. He points to airflow as a critical parameter that should remain stable through the entire maintenance cycle. That means including an additional safety factor/test block on the oxidizer exhaust fan to maintain exhaust volumes throughout the entire maintenance cycle, he says. In operation, he cautions against expecting the oxidizer to do jobs it wasn’t meant to do. “It is important to avoid treating the oxidizer as a PM control device,” he says. ‘Proper upstream PM control allows it to achieve better VOC, organic HAPs and CO destruction efficiency, while ensuring better uptime and longer ceramic heat recovery media life,” he says. When emissions control systems struggle, the root cause is often buildup that restricts flow and reduces control efficiency. “The most common cause of downtime related to the emission control systems are deposition and plugging that can reduce exhaust volumes and lead to higher PM, VOC and CO emissions,” Deemer says. He describes how deposition undermines wet ESP performance: “Deposition in the wet ESP collection tubes causes a reduction in power input, that allows more PM to escape to the downstream RTO,” he says. And in oxidizers, buildup can snowball into both performance and durability issues. “Buildup in the RTO heat recovery ceramic media increases pressure drop, increases CO emissions and allows alkaline particles to attack the upper layers of the RTO heat recovery ceramic media,” Deemer says.What Regulators are Watching From Deemer’s perspective, regulators increasingly want plants to have some leeway and not to operate at or near maximum allowable levels. “The regulators focus on having tolerance or room in the air permit, avoiding being on the razors edge of compliance,” he says. “They care about the dispersion modeling, stack height and fenceline concentrations of the various pollutants,” he says. And day-to-day, regulators want proof of control performance between stack tests. “They also care about the reporting of the performance indicators such as temperatures in the RTO or RCO, voltages in the wet ESP, water flow in the scrubber, etc.” Deemer says one of the best ways to avoid new facility startup delays is to align permitted limits with what control technologies can reliably achieve in practice. “It is highly recommended to work with an OEM to ensure the permitted emissions are achievable,” he says. “There are limitations with testing at very low concentrations and sometimes additional features or considerations are necessary to ensure the system will achieve compliance.” Odor and visible emissions can become an issue of contention for pellet plants, particularly those near communities. Deemer says the standard emissions control toolbox is generally effective at addressing both issues. “The typical emission control devices such as wet ESPs, RTO and RCO systems do a great job of controlling the visible emissions and odor,” he says—and it’s pretty straightforward. “Reduction of PM and destruction of VOCs eliminates odor and visible emissions,” he says, adding that “baghouses, wet scrubbers, wet ESPs, RTOs and RCOs are the most common control devices.” Unconventional Pellet Projects While wood pellet plants already manage challenging air streams, black pellet production introduces additional layers of complexity. “Black pellet production involves different drying conditions with reduced oxygen and additional processing steps versus conventional pellets,” Deemer explains. Those differences can translate into different exhaust characteristics, different deposition behavior and, ultimately, different requirements for downstream emissions control systems. Deemer notes that a bagasse pellet plant often looks different from an air emissions perspective than a wood-based facility. “The emissions from a bagasse pellet process have significantly less VOCs and condensable particulate matter,” he says. However, he cautions that bagasse brings its own wear-related challenges. “The particulate matter emissions contain more silica than wood based pellets, which is more abrasive on rotating equipment.” For newer pellet and biomass projects, Deemer’s advice starts with early engagement. “Involve the emission control OEMs to understand what performance is attainable with each technology,” he says. From there, he encourages teams to scrutinize assumptions. “Understand what design safety factors are being used, ensure it is adequate and that it covers all scenarios, such as seasonal operation challenges.”&nbsp; He suggests projects look closely at design features that influence maintenance and flexibility. “Ask about optional features that can reduce maintenance, conserve energy and provide operational flexibility,” he says. When comparing technologies, Deemer says details matter, including “materials of construction, insulation systems, heat recovery media composition, wet ESP collection tube geometry implications, wet ESP cleaning systems, details on the wet ESP quenching and recycle water system.”Tighter Targets, More Monitoring, Higher Expectations As for regulatory changes on the horizon, Deemer expects emissions targets to tighten over the next several years, particularly for particulate control. “The emission targets for the various sources will be reduced,” he says. “The change to the U.S. EPA PM 2.5 regulations will necessitate higher PM removal.” He also anticipates more stringent monitoring and reporting to demonstrate compliance between stack testing intervals, and a broader push for reliability: “Plants will push for higher uptime and reliability with the emission control equipment,” he says. In parallel, Deemer says safety features will draw more focus. He expects “stronger focus on equipment features that limit fire and explosion risks, such as ducting systems to the emission control equipment that are continuously cleaned with automated features.” Finally, Deemer believes service support will become a more central part of the emissions control landscape. “We anticipate more reliance on service-oriented OEMs to assist mills with the inspections and troubleshooting of their systems,” he says. NESTEC, he notes, launched a service program to meet that demand. “NESTEC launched a program called ServiceTrack in 2025 to provide remote monitoring, key performance indicator dashboards, inspection services and emergency troubleshooting,” Deemer says. “This program allows customers access to our expertise, while improving planning and equipment operation. This type of service will become more commonplace.” &nbsp; Author: Anna Simet Director of Content &amp; Senior Editor Pellet Mill MagazinePrinted in Issue 1, 2026 of Pellet Mill Magazine

2026-03-02 - Emissions Control Design at Modern Pellet Plants (Biomass Magazine)

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As the wood pellet industry faces tightening emissions standards and expands to include advanced pellets and unconventional feedstocks like bagasse, emissions control is becoming more nuanced and more operationally critical. 

Emissions Control Design at Modern Pellet Plants

Emissions Control Design at Modern Pellet Plants

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Emissions Control Design at Modern Pellet Plants