Bunker silo being filled. Photo from ARK Agriculture
Farmers Silage

Considerations for designing a silage clamp/ bunker silo

When fields are used for agricultural production, it is necessary to consider several aspects that influence the production of quality products. In this case, we will analyze the importance of good silage storage management and the use of a silage clamp/bunker silo.

In this post we will answer the following questions:

  • Why should a silage clamp/bunker silo be used?
  • What type of system should be used to store silage?
  • What elements should be considered when designing a silage clamp/bunker silo?
  • Is it important to consider the weight to be supported by the silage clamp/bunker silo? What type of wall should be installed?
  • What materials are recommended to create the base of the silage clamp/bunker silo?
  • What safety measures should be taken in a silage clamp/bunker silo?
  • How much does it cost to build a silage clamp/bunker silo?
  • Is there any difference in silage handling in the UK compared to the US?
  • Why use a good silage clamp/bunker silo?

According to Will Wilson, silage storage specialist and Business Development Manager at ARK Agriculture, having a good silage clamp/bunker silo is crucial to avoid losses in crops that are used to obtain products for livestock feed for example.

Once farmers harvest the feed/food from the fields, they do their best to preserve it as long as possible and in the best condition, so it is important to have good silage storage to minimize the risk of loss.

Wilson points out that while there are losses that can occur as a result of poor practices during the harvesting and ensiling process, the truth is that, in the case of forages and grasses, many of the losses come from within the trench, known as respiration and fermentation losses, which are infrequent and sometimes difficult to recognize.

Therefore, good silage trench design is vital, as these respiration and fermentation losses can reach 10% quite easily, being significantly higher in poorly designed silage storage.

“If you also add the losses that can occur from the surface, causing moldy silage, you can get up to 20% of material lost during the silage storage process. In other words, if a farmer invests a million pounds in poor quality trenches, the producer must consider a loss of 10% or 20% of material each year, aside from the investment necessary to replace that lost silage,” explains Wilson.

Selecting the best silage storage will ensure the financial and productive success of livestock or dairy farms growing anaerobic digestion plants. For more information about this, we recommend reading our article on silage techniques and their advantages.

What type of system should be used to store silage?

Everything will depend on the geographical area where the crop is located and the specific requirements of each silage.

In the case of the UK, there are four different and fairly common ways of storing silage:

1. Arch or system of sloping walls

It is a system of sloping walls where there is a concrete panel against an earth bank, which allows for better compaction and it’s also safer.

The idea is that farmers or agricultural producers are encouraged to use this system of sloping walls, although one of the disadvantages is that they tend to occupy a lot of space, so this system is ideal for those who have enough space on their farms.

Photo from ARK Agriculture. Empty silage clamp

Photo from ARK Agriculture. Empty silage clamp


This is the most recommended type of silage clamp/bunker silo design.

2. Silage bags

The silage or silo bag is one of the best-known systems and is quite common in locations where the climate tends to be very dry, so it is often used to dry and clean the grains.

Agricultural producers in the UK are used to store grass or corn silage. Among their advantages is their flexibility, allowing you to easily increase your storage capacity by purchasing a larger silage bag, for example.

Another advantage is that you can store it wherever you want. For example, you could store silage close to the area where you will use it.

The slight disadvantage of the bag system, as Will Wilson explains, is that they are difficult to handle in winter, so an open area where there is concrete to place them on is recommended. If they are left in the field, and the field becomes very muddy, the process of handling or emptying them becomes a challenge, running the risk of contaminating the forage.


Silage bags

Silage bags

3. Trench with vertical walls

This is an old-fashioned system that, as the name suggests, is based on vertical walls with steel poles protruding into the air.

The challenge with these trenches is the fact that they aren’t always designed to withstand the weight of modern machinery since they include concrete panels and vertical steel beams.

Most of these structures are usually designed and built by the farmers themselves, without considering the specifications to tolerate the weight of tractors, for example, so they are not always stable in terms of design. These structures run the risk of falling, in addition to having potential leaks.

The truth is that this type of silage trench is still in use, perhaps because it is a simple, standard design that’s also inexpensive and relatively easy to build.


Photo from ARK Agriculture. Trench with vertical walls

Photo from ARK Agriculture. Trench with vertical walls


4. Field silage

Interestingly enough, this is one of the systems still in place on several farms in the United Kingdom.

It is basically a flat platform used to store silage. Sometimes it can be located in a corner of the field or on a concrete platform, depending on the size of the facility.

The main challenge of this system is contamination because if the leachate from the silage is not properly managed, it can contaminate the silage and end up in water courses, generating an environmental problem, not only for the farm but also for other communities.

There are specific cases of farmers who had to pay heavy fines to compensate for contamination damage, also losing large percentages of stored material due to loss of quality.

For this reason, it is recommended to be extremely careful when opting for this silage storage system and to evaluate whether it can become more costly overall considering that losses could exceed gains.

In this type of silage trench design, it is very difficult to control the quality of the stored material.

For further interesting data, we recommend reading our article on the role of silage in the meat industry.


Photo from ARK Agriculture. Open field silage

Photo from ARK Agriculture. Open field silage


What elements should be considered when designing a silage clamp/bunker silo?

According to ARK Agriculture’s guidelines, when it comes to a new design, the first thing to do is to define the quality of the silage to be obtained to determine which type of silage clamp/bunker silo is the most suitable to guarantee the quality of that silage.

In this way, not only the materials to be used to achieve the best possible result are defined, but also the measurements that the silage clamp/bunker silo will have such as height, width, and depth, among others.

According to Will Wilson, many people worry about whether or not a back wall should be placed in the silo trench. However, Wilson believes that this is not necessary since it doesn’t directly influence the stability of the other silage trench walls. Wilson assures that the most important thing is to focus on other aspects such as the dimensions, which should be determined by the following:

  • Feed rate: how fast the silage clamp/bunker silo is filled or emptied.
  • Required capacity: number of tons that can be stored according to the type of silage.
  • Site availability: having enough space to locate the silage clamp/bunker silo and the possibility of expansion of the space.
  • The number of cuts and type of silage: define whether it will be one or several trenches to store the different types of silage.
  • Cover designs: choosing the best silage cover to fit the silage and trench requirements.
  • Possibility of filling and emptying the trenches using the agricultural producer’s machinery.

We recommend watching our webinar on silage clamp design with Will Wilson for more details on each of the aspects considered in the design.

Where is the best place to locate a silage clamp/bunker silo?

We cannot always choose the ideal place to build the silage clamp/bunker silo, as it often depends on the available location. However, the recommendations would be as follows:

  • It should be located above the dirty water management system, so that liquids generated from silage storage, which could be potentially contaminants, could be drained there by gravity.
  • It should not be located in front of the airflow.
  • Preferably place it in the opposite direction of the sun to avoid sun exposure most of the day. Any change in silage temperature tends to result in higher losses.
  • Consider the regulations of each country regarding the distance that a silage clamp/bunker silo should have with regards to nearby water course.

Is it important to consider the weight to be supported by the silage clamp/bunker silo?

This is a very important aspect to be considered in the design of the silage clamp/bunker silo.

As Wilson explains, “traditional silage clamp/bunker silos are rarely designed with a specific load in mind. However, it is very important to consult a specialist to make the necessary estimates to match the volume of silage you want to store.”

At this point, it must be remembered that the machinery used in the silage clamp/bunker silos can weigh more than 30 tons, the density of silage has also increased over the years, so special walls must be placed with specific measurements well thought out to support not only the amount of weight but also the movements of the machinery inside the trench.


Bunker silo

Bunker silo


What type of wall should be placed in the silage clamp/bunker silo?

This will depend on the space available and the specific requirements of each trench. In this way, the farmer can decide what type of walls will work best, whether they are vertical or sloped, single or double.

The design of the silage clamp/bunker silo must be adjusted to the parameters of the customer and the machine operator, which are:

  • Budget
  • Space
  • Time
  • Field conditions
  • Regulations

For example, if the study results determine that it is necessary to place sloping walls, but the client doesn’t have the estimated budget, adjustments can be made in terms of space, type of materials, time of construction, etc. So, it is possible to obtain another type of trench, which costs less but is just as efficient.

What materials are recommended to create the base of the silage clamp/bunker silo?

This is one of the most frequent doubts, and although many people would consider that concrete is the best option, the truth is that asphalt is recommended to create the base of the silage clamp/bunker silo since it offers higher resistance to face heavy machinery.

The following are the advantages of asphalt as a material to create the base of the silage clamp/bunker silo:

  • It can be installed in one day and takes about two to three days to cure, compared to concrete which can take about six weeks.
  • It requires fewer joints, so there is less risk of damage due to expansion.
  • It can be repaired and it’s easy to replace if needed.
  • It can be easily sculpted to create the correct slopes and levels required.

It is important to choose a type of asphalt that is resistant to acids from leachate.

What safety measures should be taken in a silage clamp/bunker silo?

The design of the silage clamp/bunker silo is important from a quality and efficiency point of view, but safety must also be considered.

According to Wilson, managing a silage clamp/bunker silo is one of the most dangerous jobs on a farm for several reasons:

  • Operators remove the plastic covers without assistance.
  • They require working at a certain height, so farmers often have to climb to the top of the trench to do some maneuvers.
  • They are at the mercy of the weather (rain, darkness).
  • They are not stable surfaces, either because of the amount of silage or because of the incidence of the weather.
  • The sides of the silage can collapse.

In this case, it is necessary to design a safety plan to ensure that the work carried out in the silage clamp/bunker silo doesn’t endanger the life/integrity of the workers.

The following are some good alternatives:

  • Consider the possibility to have workers working in pairs
  • Install fall detection systems, as workers will have to climb to the top of the silage.
  • Build trenches in protected areas or areas that can be covered, whenever possible.
  • Avoid walking near an open silage trench or instead stay inside the vehicles.
  • Stay away from the sides of the silage clamp/bunker silos and remember to have tools available to uncover the trenches without posing a risk to anyone.

What other aspects should be considered with a silage clamp/bunker silo?

Compliance with local laws is an aspect that is often overlooked and can cause inconveniences to agricultural producers.

It is recommended to study and consider the local laws of each country or region regarding the drainage of a silage clamp/bunker silo, not only to avoid penalties but also to prevent environmental pollution.

The leachate from the silage clamp/bunker silo must be properly managed. This liquid can endanger wildlife if it reaches water sources such as rivers or lakes, due to a design flaw or to cut costs.

It is important to make a good investment when it comes to silage storage alternatives because, although it is the cheapest feed, it is also the most valuable feed for the animals on a farm. The better the silage storage, the better the silage quality, the lower the percentage of losses, and the better fed the animals will be.

In addition, it is always a good idea to take care of the food to have reserves throughout the year, since unforeseen and unplanned scenarios may also arise.

It is very difficult to change existing silage storage, as it is rarely empty, so it is advisable to maintain constant monitoring to make timely repairs such as painting walls, repairing joints, as well as tearing down and building new structures if necessary, since after all, this is a long-term investment whose design will probably need to be readjusted over time.

How much does it cost to build a silage clamp/bunker silo?

This is one of the most frequent doubts. However, according to Will Wilson, everything will depend on the geographical location where the silage clamp/bunker silo will be built, the specific requirements, the materials to be used, the type of construction to be carried out, and, above all, the extension of the land where the silage clamp/bunker silo will be located.

Since this is something very specific, it is not possible to have a single cost-figure that fits all cases, but an exercise could be done considering the unit of the cubic meter.

“In this case, we will consider the silage clamp/bunker silo using the cubic meter as a volume value, so a lateral area between 40£ to 50£ (GBP) per cubic meter could be built.”

Is there any difference in silage management in the UK compared to the US?

Maybe one of the biggest differences is that in the UK there is not as much space, so historically farms have always been smaller. For example, you still see farms that have 100 cows, so the infrastructure has been built around that small farm design.

However, in the United States, there are larger farms that even have room to expand, so their trench-type silos tend to be larger due to the amount of feed they produce on their farms, their ability to expand, and the amount of labor they have available.

While in the United Kingdom trench silos are larger in terms of height and on the sides, in the United States they become more extensive because they have enough land to do so.

Likewise, regulations in both countries are different, which is another differentiating factor.

But they have the same objective in both countries: to store most of the potential crop in a silage clamp/bunker silo so that it can be fully used during the winter.

For further information, we recommend watching our webinar on silage clamp/bunker silo design.

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