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Agricultural Silos

Agricultural silos are structures designed for the storage of bulk materials—usually grain—while keeping them (relatively) dry and cool. Silos aid growers by allowing them to save their product for times when it will fetch a higher price than at harvest time, and they allow purchasers to save money because when they can store more they can buy in bulk.
Corrugated (galvanized) silos by smooth wall (carbon steel) silos
Stainless Silos for Wine

Types of Silos

“Silo” is technically a general term meaning a place of storage, but in the industrial/agriculture space it has a more specific meaning. Tower silos are the most common type, and are what most people mean when they say “silo” but there are others.

Tower Silos

The most common are tower silos, which are tall, vertical structures usually made of stainless steel, carbon steel, galvanized steel, or concrete. This method is so popular because it saves space, it’s easiest to ship, and it’s great at keeping dry product dry. And because stainless is an option, it can store products that others cannot. They are commonly used for storing silage, which is fermented feed made from crops like corn, grass, or alfalfa.

Bunker Silos

Bunker silos are horizontal storage systems constructed from concrete or earth walls. Crops are packed tightly into these silos using heavy machinery and then covered with plastic sheeting to create anaerobic conditions ideal for fermentation. These silos are better in hotter climates because they keep the product closer to the ground where it’s cooler, when the product isn’t dry and needs to air out, and when you want to drive a tractor in and drop the material off rather than blow it into a tall container.

Uses

Silos serve several key purposes in agricultural practices:

Grain Storage: Silos protect grains like wheat, corn, rye, oats, cereal grain, millet, rice, and buckwheat

Silage Storage: Farmers use silos to store silage, a high-moisture feed for livestock. Proper storage ensures nutrient retention and prevents spoilage.

Feed Storage: Many livestock farms use silos to store mixed feed or other bulk feed ingredients.

Construction Materials

Silos are constructed from a variety of materials, each chosen for its specific benefits:

Concrete: Durable and can be built much bigger than a shipped vessel could be.

Stainless Steel: Strong, relatively light, and extremely resistant to weather and pests.

Carbon Steel: Strong, resistant to weather and pests, cheaper than stainless

Galvanized Steel (material in corrugated silos): Cheap, cheap to ship, and can be larger than is shippable because they can be easily constructed on-site. Are seldom used when small because they will rust and will fall apart sooner, especially if being pneumatically filled.

Corrugated/galvanized silos
Corrugated silos using bucket elevators

Advantages and Challenges

Pros:

Protection from weather, pests, and spoilage
Efficient use of space, especially in vertical designs
Facilitation of fermentation for livestock feed

Cons:

High initial investment for construction and setup

Features

Modern agricultural silos come equipped with a variety of features designed to improve their suitability for the material you’re storing. These features vary depending on the type of silo and its intended use, but common ones include: 

Filling Systems

Filling Lines: Pneumatic systems blow material through pipe.
Augers & Screw Conveyors: Helical conveyors inside the silo to evenly distribute materials during filling.

Unloading Gates and Mechanisms

Knife Gates: Bottom gates that slide open and closed, allowing materials to flow out by gravity; common in grain silos.
Rotary Valves: Rotating paddle gate that controls flow and allows for pressure differentials; necessary for pneumatics and chain disks
Sweep Augers: Devices at the base that rotate to move grain toward the unloading point.
Conveyor Belts: Used in bunker silos to extract materials. 

Corrugated silos using screw feeders for filling
Bunker Silo with grain in it

Aeration and Ventilation Systems

Fans: used to circulate air and prevent moisture buildup
Ventilation Ducts: Facilitate uniform airflow throughout the silo for even drying and temperature control

Temperature and Moisture Sensors

Installed to monitor the internal environment and maintain optimal storage conditions 

Safety Features

Pressure Relief Valves: Release pressure buildup caused by combustible dust explosions
Explosion Vents: Panels that open in response to an explosion to preserve the silo structure
Dust Collectors: Reduce the accumulation of combustible dust
Ladder Cages: Protect workers when they need to climb the silo for maintenance; not often needed
Gas Monitoring: Sensors to detect harmful gases, such as carbon dioxide, methane, or ammonia, particularly in silage silos.

Fill Level Detection

Weights and bobbies, lazer, sonic, or visual, there are a number of ways to monitor fill level. To learn more about this, click the header above. When exact fill level is not important and you just need to see when you’re low, you can opt for a sight glass on the side so you can see when it’s low.

Protective Features

  • Weatherproofing
  • Seals, coatings, and designs to protect against rain, wind, and UV damage.
  • Insulated walls to protect against extreme temperatures.
  • Rodent guards and tight seals to prevent infestations.
  • Smooth interiors that minimize hiding spaces for pests.
  • Reinforced walls for heavy loads and prevent collapse, especially in large silos.

Specialty Features

Partitions: Allow for storage of different materials within a single silo.

Oxygen barriers and airtight seals: Ensure anaerobic conditions for fermentation.

Chilling or drying systems: Integrated equipment to dry or cool grains before or during storage.

Fumigation ports: Allow safe introduction of fumigants for pest control.

History and Evolution

Depending on how you define silos, they’ve been around as long as mankind. But the modern design of silos is agreed to be invented in the second half of the 19th century by the famous American agrarian Franklin King. Before manufactured silos, product would be dumped in pits or trenches lined with clay to keep it dry and cool. The adoption of modern silos played a significant role in the industrialization of agriculture, enabling large-scale farming and enhanced food security.

Silos are used worldwide and adapted to suit local agricultural practices. In developed nations, large-scale silos are common for industrial farming operations, while smaller or temporary silos are prevalent in developing regions. Innovations such as hermetic storage systems are helping reduce grain losses in regions with limited infrastructure.