Flat Bottom vs Cone Bottom Silos: Which is Right for Your Grain
Choosing the right grain silo is an important investment decision. The type of silo you select can influence storage capacity, grain handling, aeration, unloading, site layout and the way your storage facility operates for many years to come.
Two common options for permanent grain storage are flat bottom silos, also known as on-ground silos, and cone bottom silos, also known as elevated or hopper bottom silos.
While both can provide effective long-term grain storage, they are designed to meet different operational requirements. Understanding the advantages of each can help you determine which configuration is best suited to your farm or commercial grain storage facility.
What is a Flat Bottom Silo?
A flat bottom silo is constructed on a concrete foundation, with the grain stored directly above a flat or near-flat floor.
Flat bottom silos are particularly well suited to large-volume grain storage. Kotzur's on-ground range includes models designed for rural and commercial applications, with individual silos capable of storing thousands of tonnes of grain.
Rather than relying solely on gravity to empty the silo, grain is typically discharged through an unloading system. Sweep augers can then be used to assist with removing the remaining grain.
1. Advantages of Flat Bottom Silo
1.1 Large storage capacities
One of the key advantages of a flat bottom silo is its ability to economically accommodate large volumes of grain.
Kotzur's current on-ground range extends from the smaller GP Series silos through to very large commercial storage configurations. For example, the GP36 range extends beyond 17,000 tonnes nominal wheat capacity in individual models, providing considerable flexibility when designing large storage facilities.
This makes flat bottom silos particularly suitable for growers, commercial grain handlers and larger operations where maximising storage capacity is a priority.
1.2 Effective aeration options
Aeration is an important part of maintaining grain quality during storage.
Kotzur flat bottom silos can incorporate in-floor aeration for cooling, while full-floor aeration systems can provide the higher airflow required for aeration drying.
Full-floor aeration can provide highly even air distribution throughout large flat bottom silos, although the design and cleaning requirements of the aeration system need to be considered.
1.3 Flexible storage configurations
Flat bottom silos can form part of much larger integrated grain storage and handling systems.
Kotzur can incorporate different unloader configurations, conveyor roof loads, custom silo sizes and geometries, and designs for high-wind or seismic regions. Storage and conveying systems can also be designed as an integrated solution.
Multiple silos can also be connected by walkways, with access available via ladders or spiral staircases.
1.4 Things to Consider with Flat Bottom Silos
The main operational difference is unloading.
Because there is no hopper directing the entire contents towards the outlet, mechanical equipment is generally required to completely empty a flat bottom silo. The unloading system therefore becomes an important consideration when designing the overall storage facility. These unloaders are available in either electric, hydraulic or PTO variants.
Hygiene and clean-out should also be considered when selecting any grain storage system. Residual grain can provide an environment for stored grain insects, making effective clean-out an important component of silo selection and ongoing grain-storage management.
What is a Cone Bottom Silo?
A cone bottom silo stores grain above an elevated hopper or cone, allowing the stored product to flow towards the discharge point using gravity.
This design can provide a significant operational advantage where grain needs to be emptied frequently, transferred quickly or incorporated into a handling or processing system.
Kotzur's Large Elevated Sealed Gastight Silos use a hopper design specifically intended to facilitate rapid emptying.
2. Advantages of Cone Bottom Silos
2.1 Fast, efficient unloading
The most obvious advantage of a cone bottom silo is gravity discharge. Instead of requiring a sweep system to move the remaining grain across a flat floor, the cone directs the product towards the outlet.
For operations regularly moving grain in and out of storage, this can simplify the unloading process and improve turnaround times.
2.2 Different cone angles for different applications
The angle of the cone is an important consideration because different grains and bulk products have different flow characteristics.
Kotzur's large elevated silo range includes 35°, 40° and 45° cone configurations, depending on silo size and application.
A steeper cone can assist the flow of products that do not discharge as readily, while the appropriate configuration should ultimately be determined by the commodity being stored and the requirements of the overall handling system.
2.3 Well suited to frequent grain movement
Cone bottom silos can be particularly useful where stored grain is regularly transferred to another process or piece of equipment.
Applications might include:
- · feedlots and feed milling
- · grain processing facilities
- · seed handling
- · commercial grain storage
- · blending and segregation
- · load-out systems.
2.4 Easier complete discharge
Because gravity assists the movement of grain towards the outlet, cone bottom silos can reduce the amount of grain remaining inside after unloading.
That can be particularly valuable where hygiene, segregation or frequent changes between stored commodities are important considerations.
| Consideration | Flat Bottom Silos | Cone Bottom Silos |
| Storage capacity | Particularly suited to high-volume storage | Typically selected where efficient discharge and grain movement are priorities |
| Unloading | Mechanical unloading and sweep systems | Gravity-assisted discharge |
| Clean-out | Requires an appropriate clean-out system | Hopper assists complete discharge |
| Aeration | Well suited to in-floor and full-floor aeration systems | Aeration can be incorporated depending on design and application |
| Site Infrastructure | Constructed on a concrete foundation | Elevated on an engineered support structure |
| Best suited to | Large-volume and longer-term storage | Frequent unloading, segregation and integrated handling/processing |
| Kotzur options | Extensive range of on-ground capacities and configurations | 35°, 40° and 45° hopper configurations |
Importantly, neither design is inherently "better". The right silo depends on what you need the storage system to do.
3. What About Sealed Grain Storage?
Whether you choose a flat bottom or cone bottom silo, sealing capability should be an important consideration when storing grain for extended periods.
Kotzur's on-ground sealed silos are designed for medium and long-term grain storage and are manufactured to support phosphine or controlled-atmosphere fumigation.
Kotzur's large elevated sealed silos are likewise manufactured to AS 2628, including the five-minute half-pressure decay standard.
Effective gas-tight storage is an important component of stored-grain pest management. When purchasing a new silo, look for gas-tight sealability to AS 2628, particularly where phosphine fumigation is required.
4. Can You Use Both Flat Bottom and Cone Bottom Silos?
For many grain storage facilities, the best solution may actually involve both silo types.
A large flat bottom silo might provide economical bulk storage, while smaller elevated silos can provide segregation, rapid discharge or temporary storage before grain moves into another process.
This is where looking at the entire grain handling process, rather than selecting individual pieces of equipment in isolation, becomes important.
5. Finding the Right Grain Storage Solution
At Kotzur, we design and manufacture grain storage and handling solutions for Australian farms and commercial operations.
Our range includes on-ground flat bottom silos and large elevated cone bottom silos, with options for aeration, grain handling, access systems and integrated storage facilities. Kotzur silos are engineered for Australian conditions and can be modified to suit specific customer and site requirements.
The best storage solution isn't simply about choosing between a flat bottom and a cone bottom. It's about designing a system that suits what you store, how you handle it and where your operation is heading.
Talk to the Kotzur team about designing a grain storage solution for your operation.