Feed storage management
June 1, 2007
Feed millers spend a great deal of time managing the technical aspects of their mills, looking at ways to control costs and improve efficiency. But once the feed is made and put in bulk bins or packed in bags and placed in the warehouse, the temptation is to consider the job completed.
But feed products can just as easily deteriorate in storage as during the milling phase. Thus, finished products are as much a part of feed mill management as any other part of the process.
So how should feed millers manage their storage facilities? First, they should start by knowing their facility and understanding the vagaries of the different areas available to them. Finished product bins are notorious for harboring infestation, and warm pelleted feed that is moved into bulk bins will sweat and create the ideal moist and humid conditions for insects to thrive and multiply.
Good ventilation is a must, and it is worth spending time to ensure that the ventilation you have installed works correctly. Free air always takes the line of least resistance and will most easily be drawn from those bins or silos nearest to the fan or prime mover. Balancing general exhaust systems over bins is an art, but it is worth spending time to get it right.
In Europe, the ATEX regulations require feed millers to pay a great deal of attention to air flows, and the regulations call for very specific localized exhaust, almost akin to one silo, one dust unit or exhauster. In large mills, this is neither practical nor economical, but the need for good exhaust is paramount to prevent mold growth.
As the diameter of a pellet increases, so does the time it takes for it to cool down properly after pelleting. It takes almost 24 hours in a warm and humid climate for the core of larger, one-inch
diameter pellets to reach ambient temperature. Cooling after pelleting only reduces surface temperatures. Although this is satisfactory for small, 1/8-inchdiameter pellets for small animals, broilers, layers, etc., the larger diameter pellets require much longer for moisture to migrate to the surface of the pellet and evaporate.
When evaporation takes place, the warm, moist air needs to be evacuated from the storage silos. A constant negative pressure is thus required to maintain the equilibrium. If you are wondering how efficient your cooling systems are, try sampling some feed an hour or so after it has been cooled and place the sample in a sealed plastic container. You will see whether it has been effectively cooled just by looking at the amount of condensation that appears in the container an hour or so later. Your exhaust system needs to be capable of removing this water vapor from your finished feed silos as moisture migrates from the pellet core.
Secondly, we need to look at silo configuration and hopper bottom design. Most millers know the angles required for product to flow easily from a silo, and they also know the type of coatings that aid proper emptying. It is still surprising, however, to see the number of out loading silos with “hammer rash” on the bottom third of the hopper where feed has had to be persuaded to come out of bins, usually as a result of being placed in poorly ventilated silos with rough internal walls or disproportionately small outlets.
When designing bins with ease of operation and compatibility in mind, it is well worth spending time to evaluate the average feed order sizes, transport fleet makeup in terms of individual truck carrying capacities and also the optimum production run size of individual ration types.
Over the years there has arisen great disparity of batch sizes and bin sizes. Truck payloads have increased, mixer sizes have increased, (usually on the erroneous assumption that bigger mixers make for more efficient mill operations), customers’ order patterns have increased and yet bulk out loading bin sizes have remained unchanged. Again, balance and forethought are invaluable in such circumstances.
And you also have bagged feed to consider. Many mills lose the plot when it comes to bagged feed storage, giving over a disproportionate amount of space to storing feed and making feed in far greater quantities than is required to fulfill the immediate orders in hand.
The most efficient mills do not store finished feed for more than 24 hours, do not have stocks available “just in case” a customer requires an order and devote little or no manpower to dedicated packing operations. That being said, there are other mills that specialize in handling bagged feed and charge for the privileges the customers enjoy of having bagged feed available at all times, whenever they wish to either collect it themselves from the mill or have it delivered in small quantities on short notice. For these millers, management of the warehouse is a crucial
part of the business and their attention is required at all times to maintain good stocks that are in sound condition, correctly rotated, labeled and fresh.
A good system of inventory control is essential in these circumstances. Accurate stock counts and inspection of “best if used before” dates are part of everyday life, as is ensuring that there is no damage to stock by fork lifts. Checking temperatures of large diameter pellets that have been packed without being left to cure in bulk bins is an important function of the warehouse superintendent. This often requires breaking down palettes to inspect temperatures of feed in the center of the stack before restacking and wrapping the feed again.
Pest control is important, and all mills with a warehouse will have a pest control contract or someone on their staff who is trained to apply pesticides and monitor the uptake by rodents of suitable rodenticides placed both inside the premises near doorways and around the outsides of the buildings. Keeping vegetation to a minimum within a few yards around all buildings will help to minimize rodent ingress into stored product warehouses.
Fumigation of storage sheds and bulk storage silos on a regular basis will keep stored product insects at bay, and the use of pheromone traps will indicate when the time is right for fumigants to be applied. It is worth noting, however, that pheromone traps are of little use during the active breeding season or when natural conditions for reproduction are right. At such times, pheromone traps can actually draw insects into an area and act as an attraction rather than simply a means of monitoring insect activity levels.
And what about raw material storage and management of facilities? The same principles apply, including:
• Inspecting silos regularly, especially dead spaces above the raw material fill line;
• Making sure bins and silos are well ventilated;
• Keeping a negative air flow at all times;
• Ensuring that inlet and outlet slides are in proper working order to avoid inadvertent cross-contamination;
• Cleaning silos on a routine basis to remove material buildup that could harbor infestation.
Millers sometimes seek to use ingredients that their facilities are not really equipped to handle. Milk powders, whey, distillery byproducts, oat flours and other difficult-to-handle materials all seem to surface periodically on the formulators screen and are purely evaluated on price and nutrient density without much attention being paid to the costs and practicalities of handling such materials.
Many of these ingredients, not just confined to the aforementioned list, are often better handled in tote bags rather than in bulk, and the use of tote bag emptying stations have often proved useful in mills where the frequent use of exotic raw materials is needed. In such circumstances, it is important to ventilate the area well for the sake of the mill operatives and also to minimize ingredient losses, especially when such ingredients are of high financial value.
There are always people in the feed milling industry with tales of exotic ingredients that were unusual in character and difficult to handle: abrasive ingredients that wore out machinery at unprecedented rates; ingredients so fine they were unable to control dust emissions; or those whose color and fineness made them so obnoxious to handle that nobody would go near them. Thankfully, most of these exotics have been progressively dropped from the formulators’ portfolio, but some remain, particularly in the organic feed mills of the world.
But irrespective of what the ingredients are or what the finished feed is made from, the basic principles of storage management apply, and these are largely based in common sense with a good understanding of the materials being handled.
Jonathan Bradshaw is a consultant to the agribusiness and food processing industries, specializing in project management and bespoke training programs through his company, J B Bradshaw Ltd. He has extensive experience in flour and feed milling in Africa, the Americas, Europe and the Caribbean. He may be contacted at: firstname.lastname@example.org .