By Jamie Swedberg
The popular image of an agricultural storage silo is of a tall, cylindrical metal structure. This type of silo is still in common use. However, methods of containing grain, fruit and other agricultural products during storage and transport are evolving quickly. Fabric plays a prominent role.
Don’t be surprised if, in the near future, you start to see extruded-plastic silage and grain storage bags dotting the landscape where metal silos used to stand. It was only a couple of decades ago that farmers began using machinery that covered their hay bales in plastic to keep them fresher. Now that grain bags are available from overseas companies such as Donaghys (based in Dunedin, New Zealand), the practice will likely become commonplace here before long.
Several companies are manufacturing soft-sided fabric silos for storage of bulk goods in warehouses. Agriculture is a new field for these firms; until recently, they’ve mainly been concerned with storing industrial compounds such as chemical powders and plastic pellets. Now their metal-framed polyester bags are being used to store everything from peas and cocoa to tea leaves and wood-stove pellets.
“There are three main benefits,” says Keith Simpson, marketing manager at Spiroflow Ltd., a Lancashire, U.K., company with a U.S. office in Monroe, N.C. “First, they are, generally speaking, lower cost than metal units. Second, they can be whatever shape you want them to be, because they are fabric. They can be tailored to maximize storage space. And last but not least, they can be folded and dismantled and taken through an average personnel door, so you can gain access to storage areas that you might otherwise not be able to use. Most metal silos are one piece and have to be put in place with cranes. So for sophisticated cooperative-type farming situations with good existing buildings, these units still offer the advantages of price, maximizing the use of space and accessibility.
Simpson emphasizes the existing buildings because these fabric silos are primarily for indoor warehouse use. Weatherproof covers are available for them, but they’re not ideal because they reduce the silos’ breathability. Woven polyester, unlike metal or other nonbreathable materials, allows air circulation, thus reducing condensation that could cause spoilage.
Many agricultural products, such as fruit and vegetables, are transported on pallets rather than in bags. Traditionally, shippers would stack these pallets in a room, then seal the room and fumigate with ripening gases and other chemicals. But Somerset, N.J.-based ITW MaxiGrip has given these companies a more manageable way of fumigating. Their extruded plastic zippers (similar to the slide zippers on sandwich bags) allow agricultural distributors to enclose and pressurize individual pallets. The distributors had experimented with this tactic in the past, but it was ITW MaxiGrip’s product that allowed the technology to come into its own.
“Our zipper just provides a better seal,” says sales engineer Joseph Cowin. “Standard zippers aren’t airtight, so previously the stuff was always leaking out and they had to work to keep the pressure up. Now they can fumigate it inside the bag while shipping it, and it gets to its destination fresher. They can also use less gas, and it is probably a safer environment for the workers.”