Odor Elimination: Rendering

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In the Rendering Industry, odor control equipment has been in use since the early 1970’s about the same time Anguil was formed and started serving clientsAnguil RTO with the best available air pollution control equipment. Typical early applications of air pollution control equipment in rendering consisted of a direct fired afterburner for destruction of the organic emissions (odor, ammonia, fats, grease, and particulate) being emitted from the cooker process. A properly designed afterburner was capable of providing reliable destruction of the organic emissions while operating at temperatures of 1200°F or higher.

As technologies evolved, fire tube boilers that utilized the waste heat of the afterburners were added to produce steam for the steam intensive plant process. The use of the waste heat boilers were the first step in heat recovery of the afterburner. The addition of the waste heat boiler to an afterburner would typically make the overall system efficiency of the two components in the high 70% to low 80% range. However, the overall system efficiency was only this high if the total production of steam from the waste heat boiler was constantly used. Intermittent use of the steam production severely lowered the overall system efficiency and increased the operating cost.

Other applications of different technologies included the use of Thermal Recuperative Oxidizers, which utilize a shell and tube stainless steel heat exchanger. The Thermal Recuperative Oxidizers were not used with waste heat boilers due to their lower outlet exhaust temperatures, but still utilized Economizer units for pre-heat of make-up feed water. Typical heat recovery performance of a shell and tube heat exchanger was around 60 – 70%. The lower efficiency of the shell and tube type heat exchanger vs. a waste heat boiler still averaged to a lower annual operating cost on applications were large boilers were already existing, and steam generated by a waste heat boiler could not be utilized on a continuous basis.

The Challenge

Rising energy costs and the social pressures for improved Environmental Social Governance (ESG) around one of the oldest recycling industries, Rendering, has led to the need for implementation of better environmental controls. With residential areas encroaching on Rendering plants, odor control of storage, loading, grinding, and transport areas has become important. The larger air flows associated with controlling these areas make the use of higher efficiency technologies a must in order to conserve energy and meet today’s carbon reduction goals.

The Solution

Regenerative Thermal Oxidizers (RTOs) are becoming more commonplace to solve these challenges, but the importance of an experienced team to supply thisAnguil RTO equipment is critical. Anguil has the experience to ensure stringent odors are minimized, proper materials of construction are used, and consideration has been made for particulate and high moisture processes. Pre-treatment is often part of an integrated RTO odor control solution in Rendering due to the difficulty in treating Ammonia (NH3) and Hydrogen Sulfide (H2S), two common components of cooker exhaust. An inlet Venturi Scrubber removes the heavy wetted particulates followed by a Dual-stage Scrubber to remove the NH3 and acid gases to prevent the formation of NOx and SO2 in the RTO.

The Result

With the multi-stage solution, the initial Venturi Scrubber uses a centrifugal action to ready the gas stream before entering the first-stage Scrubber that treats the ammonia. Leaving the top of the initial packed tower into the bottom of the Hydrogen Sulfide second-stage section, the waste gas is further prepared for final treatment of Volatile Organic Compounds (VOCs) and Hazardous Air Pollutants (HAPs). A three-canister RTO provides a means to eliminate a short duration “puff” of untreated odors from the RTO during valve cycling. With such high intensity odors in a Rendering application, it is vital to remove greater than 99% of any entering waste components. Leaving the exhaust stack of the RTO, final regulated emission levels are met while minimizing CO2 production with the highly energy efficient RTO technology.

Project Highlights
  • Stainless steel material is used to maximize equipment life when exposed to incoming acidic gas streams
  • Specially designed ceramic media heat recovery beds in the RTO to better resist particulate plugging
  • Properly sized burner and combustion chambers for maximum performance and flexibility for fluctuating operations
  • Proven controlled bake-out program to clean RTO ceramic media to maintain optimal performance

No Half-baked Idea

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The Challenge

Ready-to-eat meals, freshly baked goods, and essential groceries draw loyal customers to a chain of convenience stores; they just also happen to sell gasoline. The chain’s nutritious food is locally sourced, processed, and packaged for distribution to almost 1,000 stores in the United States. This company is uniquely positioned as vertically integrated, whereas much of the supply chain is owned by a single corporation serving a common market and customer segment.

Ductwork installation on catalytic oxidizer

One such vertical operation is a commercial bakery that supplies the company stores with fresh bread, bagels, buns, doughnuts, muffins, and snacks. It is a state-of-the-art facility focused not only on quality, but operational energy efficiency and a low carbon footprint. When the company decided to increase capacity, they took a wholistic approach to the design and layout. New bread and bun ovens were purchased along with proofers which are large enclosures kept at elevated temperatures to help dough rise. Most commercial bakery ovens and the corresponding proofers rely heavily on natural gas or electric elements to generate heat for baking the products.

While working with local regulators to satisfy air pollution control requirements for the new lines, company engineers explored the utilization of waste heat from pollution control systems. Oven exhaust contains Volatile Organic Compounds (VOCs) like ethanol, as well as odors that must be treated to comply with national emission standards.

Like many other industries, food processors often find that the best available control technologies for emission and odor abatement are thermal and catalytic oxidizers. Oxidation systems use time, temperature, and turbulence to break down pollutants into Carbon Dioxide (CO2), heat, and water vapor. This bakery was particularly focused on minimizing the CO2 output from the planned oxidizer installation by utilizing the heat from combustion. It would not only save operating costs, but also keep with the company’s commitment to do right by customers and the community.

The Solution

Anguil Environmental Systems was one of the first air pollution control system suppliers in the early 1990s to design and install oxidizers that met regulations limiting bakery oven emissions and odors. Three decades later, Anguil remains a leading supplier of both thermal and catalytic oxidizers to the baking industry. Regenerative Thermal Oxidizers, or RTOs, have been increasingly used on commercial ovens for their energy-efficiency operation. RTOs are typically 95% thermally efficient whereas catalytic oxidizers range from 60-80%. However, catalytic oxidizers are still widely applied at bakeries due to their lightweight construction which makes a rooftop installation more feasible, putting them near the ovens while eliminating costly duct runs.

Catalytic Oxidizer for Ethanol

This bakery was like many others in that regard; a roof installation made catalytic oxidation the most logical equipment selection. Two Anguil Model 50 (5,000 SCFM capacity) catalytic oxidizers would be installed, one for each oven, on dedicated roof platforms. During operation, ethanol-laden oven gases are pushed into a stainless-steel, shell-and-tube heat exchanger inside the oxidizers via a system fan. The contaminated airstream is progressively heated while traveling through the heat exchanger towards the combustion chamber. The cleanable, heat exchanger allows for self-sustaining operation with no auxiliary fuel usage at Lower Explosive Limits (LEL) levels of 8-12%. At the burner, the process gas is raised to the catalyst operating temperature. As the heated gas passes through the catalyst, an exothermic (heat releasing) reaction takes place as the pollutants are destroyed. The hot, purified air then passes through the opposite side of the internal heat exchanger and transfers thermal energy to preheat the incoming air.

This environmentally conscious bakery was interested in further reducing operating costs and energy consumption. Therefore, Anguil recommended and designed a secondary heat recovery system to capture additional waste heat from the two oxidizer stacks. Finned tube heat recovery coils with propylene glycol-heated fluid were installed to recover over 2.5 MMBtu/hr from the oxidizers and provide a heat source for the proofers.

The Result

The Anguil oxidizers achieve over 98% destruction efficiency of the ethanol emissions while reducing the carbon footprint of the bakery’s operations. The systems incorporate a self-cleaning ceramic filter, which prevents grease from plugging or fouling the catalyst. The Anguil design also ensured that the abatement devices would have no back pressure in the ductwork which could impact oven performance or product quality.

Two Catalytic Oxidizers for Bakery Ethanol

Wastewater Compliance Techniques For Food Processors

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The Challenge

Food production has always been a demanding and competitive process. Executives are constantly challenged by slow product development cycles, competition from healthier alternatives and even food fraud.  In today’s climate, producers now worry they can be perceived as environmentally and socially irresponsible, resulting in some retail chains refusing to stock their brands until they make often intensive and expensive changes.

Many producers are being hit by a second blow to their profit margins due to failing and overcapacity Publicly Operated Treatment Works (POTWs). Wastewater previously discharged with little care may now be subject to volume and contaminant surcharges as POTWs repair infrastructure and struggle to meet increased EPA discharge regulations.

Finally, treatment system operators with decades of experience are retiring and their tribal knowledge of how to run their antiquated treatment system retires with them. This leaves owners and executives wondering how to replace that knowledge base and ensure they remain in compliance.

In the face of increased regulatory control and rising environmental concerns about wastewater, food producers are looking for cost-effective ways to stay in compliance while keeping operating costs low. Anguil’s four-step approach to industrial wastewater treatment challenges can help producers address economical, operational and compliance challenges.

The Solution


Anguil Environmental provides highly engineered environmental equipment and service solutions that solve complex industrial air and water challenges. When we are aiding companies with water projects, we follow a very simple but effective process to deliver systems tailored to each customer’s specific needs.Food processor

The first step is to understand the business case.

We collaborate with the client to understand their challenges, and determine the project needs and objectives. We gather benchmark data to assist with alignment of solutions that offer the best return on investment (ROI), then work with the customer to understand their decision process and criteria to ensure we can check all their boxes. For example, is our customer willing to spend more on controls and automation to minimize operator involvement or to better deploy staff in other areas of the facility?

In this case, a client was looking at TSS surcharge costs of $40,000 per quarter and a surcharge of $20,000 per quarter for acidic discharge waters. The client was essentially looking at $240,000 in increased operating costs per year. BOD did not receive a surcharge, and overall water volume costs were negligible.

The second step is to explore and validate all treatment and operational processes in the Anguil lab.

Anguil validates all potential treatment and process options that align with the customer objectives. A client wanted to determine a solution for TSS removal below discharge requirements. We started by asking the client to send a wastewater sample to our inhouse wet lab to validate potential treatment protocols. We determined pH / polymer protocol resulted in TSS removals well below the discharge requirements. Hence, we determined a simple scheme could meet the customer’s goals.

After bench-testing provided us with a viable treatment option, we generated a simple Process Flow Diagram (PFD) to illustrate the primary equipment integrated into the treatment train. This train included the appropriate equalization and buffer tanks, pump logistics, clarifier, and a filter press for solids handling. In our discussion with the client, we offered additional options including:

  • Ballasted flocculation versus straight clarification to lessen the overall footprint
  • A rotary vacuum drum for dewatering instead of a filter press to lessen the burden on facility personnel and lower the liquid content (weight) of solids being shipped off site

Even though the customer appreciated the pros of each option, after reviewing the capital cost increase, the client decided to remain with the original approach.

The third step is a pilot system onsite to test waters in-situ:

With the client satisfied with our lab trials, we asked if they required a pilot system to validate the treatment approach insitu. When asked for our opinion on the value added, we stated we were confident with the treatment approach and market proven technologies. In this case a pilot study would not bring a great deal of value.


The final step in the process is the Commercial Deployment.

After completion of lab testing, discussion of various equipment options and testing against the business case, Anguil provided a firm proposal for a treatment system which would meet the treatment efficacy and business needs of the customer. The proposal contained detailed nuts and bolts information on the treatment system, estimated operational costs and options for installation, start-up and commissioning. The flexible approach allowed the customer to choose the package that best suited their needs. Anguil provided installation supervision while their local mechanical and electrical partners were contracted directly by the customer to install the equipment. Anguil performed a 3-day start-up and training. Anguil provided final “as-built” drawings within 2-weeks of startup and shipped spare parts the client requested. Additionally, Anguil’s Aftermarket and Service group was proactively in touch, ready to provide long term system and parts support.

The Result

Anguil followed a better approach to solving complex water challenges, which started with listening to the client’s needs and business case. Anguil advocated an efficient process that would provide the client with the information they wanted to make an informed decision.

  • TSS surcharges had risen 3x what they experienced 3 years prior
  • Without reduction, operational costs and compliance could prove negative to business growth and profitability
  • The lab trials at Anguil quickly validated the most cost-effective approach to reduce Total Suspended Solids (TSS)
  • 5-gallon sample sent to Anguil wet-lab for testing was ideal to determine equipment sizing and validate capital costs of the equipment
  • Lab trials allowed Anguil to optimize the chemistry and extrapolate an operational expense for the entire water treatment system
  • Anguil leveraged a Process Flow Diagram (PFD) to illustrate the equipment in the primary approach, while also showing options to increase automation, lower resources for solids handling, minimize moisture content in solids, and reduce overall footprint.
  • General Arrangement (GA) drawing allowed client to understand process flow
  • GA allowed Anguil to offer different options to client, such as Rotary Vacuum Drum vs. Filter Press for solids handling
  • Offering options allowed the client to make an informed decision on the system capabilities and system price point based on their decision criteria.
  • Anguil Project Manager (PM) led internal Project Launch and engineering completed necessary drawings within two weeks for customer to review and sign-off on.
  • PM launched internal kick-off meeting within 48 hours of receipt of PO
  • Nine people from nine departments attended to define and own their respective responsibilities
  • Anguil provided Installation Supervision over local contractors, who were responsible for installing equipment and handling electrical wiring to panel, equipment and pump skids.
  • Anguil provided engineering drawings to local contractors familiar with the client site to bid on mechanical, electrical
    and piping/plumbing of system.
  • All Anguil skids were self-contained, including all electrical and piping, so connection could come to a j-box or single inlet/outlet on skid

The final treatment system offered an ROI in line with management’s criteria. The system was also designed with additional treatment capacity to handle 30% growth in business and the resulting impact that would have on the treatment system. Although we did not pursue BOD in our treatment approach, we did discuss how we would determine viable treatment technologies to address it.

Organic Particulate Filtration

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The Challenge

A food products company that mixes various types of waxes and other components to make the base for chewing gums was faced with the issue of cleaning up a slightly odorous, visible emission being exhausted from two of their process lines. The components of the emission were hot particles of chewing gum and some volatile organic compounds (VOC’s). The particles would quickly clog a conventional filter system or electrostatic precipitator, neither of which could control the odor off the process line. In addition to the emission problem, the condensation of the exhaust stream was damaging the roof of the facility.

The Solution

After thorough technical evaluation, the Self-Cleaning Ceramic Filter (SCCF) was recommended as the ideal solution for processing the exhaust and Anguil Environmental Systems was selected to solve the visual, odor and VOC problem. 

The Result

In order to demonstrate to the client that this was a viable solution, Anguil utilized their portable self-cleaning ceramic filter test unit before any purchase decisions were made. During the test, the process lines were run through the ceramic filter in two modes, hot and cold.

First, the system was run in the hot mode with a gas burner firing continuously at 400º-500ºF heating up the process air. The once visible plume disappeared as it passed through the ceramic filter and catalyst module. Second, the ceramic filter was used without heat, and again, the visible plume disappeared as it passed through the ceramic filter and catalyst module. Twenty-four hours of production were run across the ceramic filter without heat and the visible emission was acceptable from a customer and environmental regulation standpoint. However, when utilizing a cold process stream, particulate matter accumulated on the ceramic filter which had to be periodically cleaned by firing the burner. When the cleaning cycle began after the two shifts, a dense white plume was emitted for 90 seconds while the filter element was burned clean. The customer, a food products company, felt that this emission level was not acceptable so they decided the continuous hot running ceramic filter would better fit their needs. It should be noted that for certain operations with visible emissions, the pulse cleaning mode may be acceptable. Many local authorities allow companies to discharge up to five minutes per hour without control.

After the customer determined that the ceramic filter would solve their problems, Anguil proceeded to manufacture and install a 1,000 SCFM (1,577 Nm3/Hr) ceramic filter unit. The unit was used to process the exhaust from two process lines. One of the more significant benefits to the company was Anguil’s ability to reduce the air volume from the processes. Initially, the two gum-based mixers each had a 3,000 SCFM (4,731 Nm3/Hr) high volume, low static pressure fan that was exhausting to atmosphere. Tight covers on the mixers minimized the escape of odor into the mixing room. With the close capture hoods it was possible to reduce the air volume from 6,000 SCFM (9,462 Nm3/Hr) exhaust to 1,000 SCFM (1,577 Nm3/Hr) exhaust from the two process lines. The net air volume reduction of 82% reduced both the capital cost and the operating cost of the system.

In order to guarantee continuous production in the event of a burner failure, Anguil installed a bypass equipped with conventional roughing filters. The exhaust fan was equipped with an inlet vane control to vary the air volume if only one process line was being used. The control panel was outfitted with a user-friendly PLC first out detection system. The entire ceramic filter system was mounted in a light-weight enclosure to allow for roof mounting without significant structural modifications to the building. Growth capacity was accommodated in the gas burner and the fan section, allowing for the addition of future operations. Anguil’s system engineering provided their client with a solution to their compliance needs at reduced air volume and reduced cost.

Meat Processing Odor Control

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The Challenge

For its first two years of production, a food manufacturer based in South Wales, England, focused its production on potatoes. Neighborhood residents voiced no complaints about odors during this time period. However, as new production lines (including barbequed meats and curried chicken) were added, the complaints began, and it became clear that odor abatement equipment was needed to resolve the issue.

Onsite meetings were held to discuss the issue, concerned citizens and the local environmental health officer attended to discuss the best way to handle the situation. The company employs a large percentage of the local residents, and was concerned about maintaining good community relationships, while at the same time it was in need of a building expansion to introduce a new line of curried chicken products. Planning approval became contingent upon the installation of an odor abatement system to control the new and existing odors.

The Solution

The two-year old factory had been designed to incorporate emission control equipment, and management was committed to installing the most effective technology available. After a thorough technical evaluation, Anguil Environmental Systems, Inc. was selected and contracted to address the odor emission problem and satisfy the building expansion requirements.

The Result

Although several odor control technologies were discussed — including masking sprays, wet scrubbing, bio-filtration, carbon absorption and catalytic and thermal oxidation — the Regenerative Thermal Oxidizer (RTO) was the only technology that could guarantee the elimination of 99% of the odorous compounds. 

Since future production may produce different odors, it was necessary that the installed technology have the ability to treat a wide range of odorous compounds to a high level of removal/destruction – guaranteed.  Although, the guarantee of nearly complete elimination of the odors was the primary concern, capital and running costs were also of utmost importance. The RTO was selected due to its low operating costs and the fact that no waste is produced as a byproduct of its functioning.

Following the installation of the RTO, the results were dramatic, and as promised nearly all of the odors have been eliminated. Due to its well-designed odor control strategy, Anguil resolved the odor emission problem, thereby resolving potential community relations/environmental issues, and meeting its requirements for obtaining planning approval for future expansions.

Bean Roasting

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The Challenge

After purchasing a new Barth roaster for their East coast processing facility, a nationally known chocolate roaster company knew their emissions and odors would need to be addressed with the increase in production.

The Solution

Emissions and odors from the bean roasting process have traditionally been treated with an afterburner which simply burns the roaster exhaust with natural gas or other fuel types. This is an effective means of air pollution control but not very economical or energy-efficient. Rising fuels costs and the sustainability concerns prompted this company to find a more energy-efficient, cost-effective means of emission destruction.

Recognizing the need for a better solution within the industry, Anguil developed a dependable system that not only accounts for the unique needs of this application but also achieves environmental compliance at a fraction of the operating cost. Expected savings for a four bag roaster can be seen in the illustration below.

Air Flow Rate Fuel Cost / Hr Savings Per Hour
Afterburner RTO
2,500 SCFM (4,012.5 Nm3/hr)  $          41.30  $               4.50  $        36.80
5,000 SCFM (8,025 Nm3/hr)  $          81.14  $               6.71  $        74.43
7,500 SCFM (12,037.5 Nm3/hr)  $        120.96  $               8.91  $      112.05
10,000 SCFM (16,050 Nm3/hr)  $        160.80  $              11.11  $      149.69


Anguil recommended an 8,000 SCFM (12,840 Nm3/hr) Regenerative Thermal Oxidizer (RTO) to handle the Barth roaster, nip grinder and alkalizer at this facility. 

The Result

With the two-bed RTO, contaminated process gas is preheated as it passes through beds of ceramic media located in the energy recovery chambers. The process gas moves from the pre-heated chamber toward the combustion chamber, where the Volatile Organic Compounds (VOCs) are oxidized, releasing energy into the second energy recovery chamber before going to atmosphere. A diverter valve switches the process gas direction so both energy recovery beds are fully utilized, providing 95% thermal efficiency thereby reducing auxiliary fuel requirements. Under normal operating conditions the unit is self-sustaining, requiring no fuel use to achieve destruction. This energy-efficient design offers significantly lower operating costs in comparison to other emission treatment methods common bean roasting facilities.

Water vapor was a major concern during the design phase of this project and therefore provisions were taken to handle the high moisture airstream coming from the roaster. Not only is water a bi-product of bean roasting but it is also added for flavor and sterilization purposes, if precautions were not taken it could have caused system components to seize during freezing weather, accelerated corrosion of carbon steel parts or even oxidizer shutdowns during high production times. Anguil engineers recommended a knock out drum with removal pump just upstream of the RTO. Modifications were also made to the fresh air damper to introduce less water vapor and portions of the ductwork were insulated to prevent freezing.

Special consideration was given to the RTO ceramic media to account for any particulate in the airstream, ensuring proper operation. The oxidizer also has a bake-out feature which works much like the self-cleaning feature on a stove. Organic particulate is regularly burned out during a high temperature cycle, this ensures that the media does not plug, reduces pressure drop and lowers electrical consumption.

In addition to the emission and odor control equipment, Anguil provided a 7,000 SCFM (11,235 Nm3/hr) Plate Heat Exchanger and corresponding duct work. This sends approximately 1.5 BTU/hr of waste heat from the RTO exhaust stack to a make-up air unit on the roof, saving the company over $80,000 a year in plant heating costs during winter months. On similar applications, Anguil has returned waste heat back to the roasters which further reduces natural gas consumption and operating costs.

The company has purchased two similar systems from Anguil for facilities in other regions of the United States. The projects have resulted in environmental compliance, lower operating costs and fewer greenhouse gas emissions for the bean roasting company at all three plants.