When the Montreal Protocol and U.S. Clean Air Act declared the fumigant, methyl bromide, an ozone-depleting chemical and phased out its use in 2005, food processing facilities were challenged to develop new solutions for managing insect pests.
Registered for food processing facilities, cylinderized phosphine is an option. However, it tends to corrode metals especially at high humidity levels—and therefore is not commonly used. Sulfuryl fluoride, a non-ozone depleting fumigant, previously used for termite management, quickly became an alternative to fumigate food processing facilities. Sulfuryl fluoride dosages needed are three times that of methyl bromide, and at temperatures below 81 degrees Fahrenheit, it is less effective against the eggs of stored-product insects.
To discover safe, effective alternatives to manage the insect populations, entomologists and practitioners looked to heat. Thermal remediation, often referred to as heat treatment, is a method of heating a mill between 122 and 140 degrees Fahrenheit to strategically eliminate insects.
Insects may try to “hide” within equipment or hidden spaces to escape the heat treatment.
Bhadriraju Subramanyam, PhD, professor at Kansas State University, studies heat treatment and other tactics for managing insect pests in grain, food, and feed manufacturing facilities. His research shows that heating food processing facilities between 122 and 140 degrees Fahrenheit will kill insects at all life stages, without introducing harmful chemicals. The treatment must be maintained over a period of 24 hours so the heat can penetrate cracks, crevices, and equipment, ensuring there is no place for the insects to seek refuge from the heat. In addition, facilities must undergo thorough sanitation prior to heat treatment.
According to Dr. Subramanyam, the optimum temperature for maximum insect survival, development, and reproduction is between 82 and 90 degrees Fahrenheit. Lower and upper temperature limits, in general, for stored-product insect existence are between 55 and 105 degrees Fahrenheit. Temperatures 122 degrees Fahrenheit or above can disrupt the ionic balances across cell membranes, injure cellular DNA, dehydrate insects, destroy protein synthesis machinery, or denature enzymes—all of which can cause insect death. Depending on the insect species and the life stage exposed, death occurs within minutes to hours at these high temperatures.
While high temperatures are an important factor, maintaining the temperature for a sufficient time is also critical because heat needs to encompass all parts of the facility. For example, insects may try to “hide” within equipment or hidden spaces to escape the heat treatment. To eliminate this risk, it is important to thoroughly clean the facility and equipment, and maintain high temperatures (target 135 degree Fahrenheit) for at least 24 hours. According to Dr. Subramanyam’s research, a typical heat treatment from setup to cool down lasts about 30 to 48 hours. Insects may also seek refuge in product spillage. Removing any food products and packaging materials is critical to mitigating this risk.
Risks of Heat Treatment
While heat treatment is an optimal solution for managing pests, it can present risks to the facility if the temperatures are not properly controlled. Excessive, prolonged heat can potentially damage the mechanical structure in facilities, or even its electrical components. Since materials expand and contract at different rates, mechanical components or even the building structure can be compromised if temperature is elevated too quickly. Furthermore, electrical components exposed to excessive heat outside of their recommended operating temperature can fail. The rate of heating should be slow and a temperature of 122 degrees Fahrenheit should be attained in about 10 to 12 hours.
Temperatures should not exceed 140 degrees Fahrenheit.
In addition to costly repair and replacements, damaged mechanical structures and equipment can have a significant impact on production—causing downtime.
As the heat treatment is progressing, check temperatures in locations where you suspect insects are commonly found to ensure temperatures are above 122 degrees Fahrenheit. If temperatures are below 122 degrees Fahrenheit, insects will survive; therefore, move fans to eliminate “cool spots” or place additional heat sources in the area. Properly monitoring temperatures will ensure optimum results. Dr. Subramanyam’s research in commercial facilities has shown that the speed of insect death was positively related to how quickly temperatures reached 122 degrees Fahrenheit, and negatively related to how long temperatures were held between 122 and 140 degrees Fahrenheit.
While high temperatures are an important factor, maintaining the temperature for a sufficient time is also critical because heat needs to encompass all parts of the facility.
Monitoring Temperature During Heat Treatment
Accurate and consistent temperature monitoring during heat treatment processes is crucial to protect valuable mechanical devices and facility structures; protect electrical components; and ensure all areas of the facility have reached and sustained effective temperatures to minimize the possibility of pests repopulating.
Since most food processing facilities weren’t built to accommodate heat treatment monitoring, facility managers are required to retrofit temperature monitoring tools and equipment—often having to run lengthy amounts of cable before each scheduled heat treatment.
A seven-story flour supply mill in the Midwest installed resistance temperature detectors (RTDs) throughout their mill to help monitor the facility during heat treatments. Prior to each heat treat, cabling was run to the RTDs. Some points were easy to access with cabling, while others were more remote. Since flour mills have multiple stories, the process was labor intensive and time consuming.
The mill eventually installed a wireless network to access temperature information throughout the facility without running cables to the RTDs. Wireless nodes were wired to the RTDs and mounted remotely throughout the facility. The RTDs signal is communicated through the node and transmitted wirelessly to a remote gateway. The gateway was able to communicate temperature data to the centralized control, which would log the data and post results on an HMI.
By using wireless technology, grain mill operators can reliably monitor any remote area while communicating temperature status.
Radio and I/O terminals contained within a single housing unit rated IP67— reduces the need for additional enclosures. With this setup, users have the flexibility to install, uninstall, and reinstall in a new location as heat treating cycles are complete.
To ensure scalable coverage, it’s important that wireless systems enable users to connect multiple nodes to one gateway. For example, Banner Engineering’s DX80 gateway connects up to 47 nodes—and each node can be connected to up to four RTDs.
To enable operators to communicate through steel and concrete, operators should select a 900 mhz radio because it has better penetration than 2.4 ghz radios through concrete floors and walls. Banner radios come in frequencies of 2.4 ghz or 900 mhz and up to 1 watt of power. The 900mhz radios tend to do a better job of penetrating steel walls and concrete and are often used in buildings. It is important to note that while this bandwidth is available for use in the U.S. many other countries don’t allow it. Banner also provides radios with site survey mode to allow users to send test packets of data across the network to confirm radio communication. The radios then report how many data packets were received.
Heat treatment is an EPA-compliant alternative to methyl bromide for managing insect pests in food and beverage facilities. Achieving and maintaining appropriate temperatures is important during heat treatment to ensure all insects are killed–and to protect the structural integrity of the grain mill and its components. Wireless technology provides an efficient and reliable solution to accurately monitor and control temperatures.
Schmid is the business development manager, food and beverage, at Banner Engineering. Reach him at firstname.lastname@example.org.