Dust Collection for the Pet Food Industry

The dry pet food industry is dominated by dog food and cat food, but also includes fish food, bird food, rabbit food, food for small mammals (such as mice, rats, hamsters and guinea pigs) and products for exotic animals. Some pet food companies also produce feed for larger animals and livestock, such as horses, cows, chickens or pigs. Kibble for cats and dogs—both carnivores—will typically include meat meal powders as well as processed grains and other ingredients. Kibble for small mammals and herbivores will include more grains, grasses and vegetable materials, and birdseed may include a variety of nuts, seeds, grains and dried fruits. Common ingredients in pet food manufacturing include: 

• Dried, powdered meat meals (for dry dog food and cat food) 
• Processed vegetable proteins (e.g., pea powder, wheat gluten, corn gluten meal, soy protein powder, rice powder, potato powder)
• Cereals and grains
• Nutraceuticals (e.g., synthetic vitamins and minerals)
• Preservatives, stabilizers and gelling agents 
• Palatability enhancers such as yeast or flavor concentrations 

Dust is created both at the beginning of the process, with transport and milling of bulk ingredients, all the way to the end, with weighing and packaging the finished kibble. Dusty processes include: 

• Milling and processing of bulk ingredients 
• Bulk material handling, transport and conveyance
• Measuring/pouring/dumping
• Dry mixing/batch mixing/sifting 
• Weighing and sorting 
• Packaging (box filling, bag filling, carton filling) 

• Worker health and safety: While pet food may be non-toxic, that does not mean that it is safe to breathe the dust created during manufacturing. Workers in the pet food industry may be exposed to various grain dusts, which can lead to chronic lung irritation and coughing known as “baker’s lung.” Meat meal powders are also associated with lung irritation. Other compounds used in pet food manufacturing, such as flavorings and nutraceuticals, may have additional health risks when inhaled in large quantities. In addition, workers may develop sensitivities to food ingredients with long-term exposure. And uncontrolled dust of any type is a housekeeping and sanitation consideration. Dust build-up on walking/working surfaces can create slip-and-fall hazards for workers. 
• Combustion risk: Many of the ingredients used in pet food manufacturing—including grain dusts and flours, plant protein powders and meat meals—are combustible. That means they can generate an explosion when allowed to concentrate in the air, in enclosures and conveyance systems, or inside a dust collection machine. A dust control system must be used to prevent candy dust from accumulating in the air and especially within enclosed spaces such as conveyors.
• Pet food safety and quality: Pet food manufacturers must consider both food safety and quality when controlling fugitive dust. Grain dust and meat powders provide an ideal breeding ground for many dangerous microbes and pathogens—including molds, yeasts and bacteria—which can present a danger to workers as well as the animals that eat the finished product. Beyond microbial contamination concerns, excess dust may impact the quality, flavor and desirability of the final product. It is especially important to control dust during the packaging process, including box filling and bag filling; excess dust in or on the packaged product is highly undesirable from a consumer perspective.

• Combustible dusts: Pet food dust falls under NFPA 61, Standard for the Prevention of Fires and Dust Explosions in Agriculture and Food Processing, as well as NFPA 654, Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing and Handling of Combustible Particulate Solids. Combustible dusts are regulated under OSHA’s General Duty Clause (Section 5(a)(1)) with additional requirements under the Hazardous Locations (§1910.307), Hazard Communication (§1910.1200) and Housekeeping (§1910.22) standards. OSHA’s Combustible Dust National Emphasis Program (NEP) outlines policies and procedures for inspecting workplaces that create or handle combustible dusts. Dust collection systems for food processing dusts must also meet NFPA 68, Standard of Explosion Protection by Deflagration Venting, and NFPA 69, Standard on Explosion Preventing Systems. 
• Food Safety: The Federal Food, Drug, and Cosmetic Act (FD&C Act) requires that all animal foods, like human foods, be safe to eat, produced under sanitary conditions, contain no harmful substances, and be truthfully labeled. Pet food manufacturers that do not comply with FDA food safety requirements are at risk of large fines or even suspension of their registration.
• Nuisance dusts: Many grain, plant protein and meat meal dusts fall under the OSHA definition of “nuisance dusts,” which are regulated under the general particulate matter concentration limits set by OSHA. The general limit for “Particulates Not Otherwise Regulated” (PNOLs) is 15 mg/m3 (8-hour TWA limit) for total particulate and 5 mg/m3 for respirable particulates. Employers must also follow general housekeeping standards (OSHA 1910.22, Walking-Working Surfaces) to prevent accumulation of dust on surfaces.

• Dust collection and filtration: A cartridge-style dust collector is a practical and efficient choice for most manufacturers of dry cat and dog food and other animal kibbles. Cartridge-style dust collectors have a small footprint per CFM compared to other styles of dust collectors, such as baghouse. They also have a wider range of filter options to collect even very fine dust, such as plant proteins. An efficient pulsing system must be used to pulse excess dust from fabric dust collector filters. 
• Combustion mitigation: Special care must be taken when collecting grain dust, meat meal powders and other combustible food dusts to minimize the risks of an explosion inside the dust collector. The dust collector should be equipped with a deflagration system to prevent pressure waves from propagating back into the facility if an explosion should occur.
• Filter media selection: Many pet food ingredients are hygroscopic, meaning they readily absorb moisture from the air. In a humid environment, these dusts may cake or form a crust on filters. A washable filter media can extend filter life considerably in these situations. PTFE coatings can also be used to help wet or sticky dust shed more efficiently from filters.
• Enclosure/source capture: Where possible, it is advised to use source capture to collect dust from point sources such as mixers, grinders, weigh stations, conveyor systems and silos. If the process cannot be enclosed, it is possible to create a custom hood to draw dust away from the production line as it is created. Positive and negative pressure zones can also be used to prevent dust from earlier processes and conveyor systems from propagating into areas where kibble is finished and packaged.