Studies show how silage bags efficiently maintain the quality of grain storage

As we mentioned in the post dealing with the general advantages of silo bags vs. steel silos, the first have proven to be especially efficient for food storage or grain storage, but as we will see next, they also create an environment protected from insects and diseases. When closing the bags, the oxygen level decreases and carbon dioxide increases. As a result, diseases caused by fungi and insects are almost completely eliminated, reducing the need to use chemicals on the food storage.

It is worth mentioning that, especially in the case of corn and grain silage, the mycotoxins that are mostly present are the Fusarium fungi that produce deoxynivalenol (DON) and fumonisins. These are field mycotoxins that must be controlled before storing the food, just like insect control upon harvest. For these reasons, thorough field control is crucial for the quality of the food stored. We will discuss the subject in this article and  get into more details in following posts.

Those who prefer steel silos claim that grains and corn are much better preserved in these structures and that in fact, they can better avoid the fermentation problems that can originate in plastic bags used for silage bags.

However, to demonstrate the efficiency of silage bags in maintaining the quality of the food product stored, we would like to mention several scientific studies carried out that compare different methods of food storage or grain storage and contrast them with tests to measure the nutritional value and the presence of diseases. In this post, we will make a brief summary of the results; however, for further information each of the publications can be consulted.

Studies regarding silage bags and the quality of the product or grain stored

First, let’s discuss the study “Biological utilization of insect infested wheat stored in different storage structures”, (Samuels and Modgil, 1999). This publication deals with an experiment performed during six months with wheat stored in jute bags, metal containers and polyethylene bags (silage grain bags).

The different types of storage were filled with the same wheat, and mice were fed with this wheat after six months. The food from the jute bags exhibited much higher levels of infections compared to what was stored in polyethylene bags and metal containers and, consequently, the animals registered lower nutritional values.

On the other hand, the study “Evaluation of quality attributes and the incidence of Fusarium sp. and Aspergillus sp. in different types of maize storage” (Di Domenico, Hasimoto, Busso, Coelho, 2015) also demonstrates the effectiveness of silage grain bags to maintain, in this case, the quality of corn.

The objective of this study was to evaluate the quality of corn grains and cobs stored in conventional polypropylene bags, vertical steel silos and polythene hermetic bags for 12 months. Two varieties of corn were used for the study of the parameters of “moisture content, ash, proteins and lipids, percentage of healthy grains and the incidence of Fusarium and Aspergillus species”.

These parameters were evaluated during the 12 months of the experiment in the different methods used for storage. In all cases, “it was demonstrated that polyethylene hermetic bags (silage grain bags) are a good option to maintain corn grain quality.”

In another study, “Dynamics of fungi and related mycotoxins during cereal storage in silo bags”, (Gregori, Meirggi, Pietri, Formenti, Baccarini, Battilani, 2013), it was also shown that silage bags are a safe storage method for cereals.

In this case, the objective was to evaluate how fungi and related mycotoxins behaved in the storage of cereals (corn and durum wheat) during a period of two years. To measure results, data was collected on temperature, oxygen and carbon dioxide inside the silos.

During the different evaluations over the two years, it was determined that the temperature inside the silage bag “followed the trend of the outside temperature, with a more limited variation. A decrease of O2 was observed from 16.4% to 2.0% for the corn and from 15.7% to 15.1% for the wheat; the decrease was balanced by the increase in CO2. There were minor variations in the activity of grain water and CFU (colony forming units) and the mycotoxin content did not change significantly during the storage period; the results were consistent in the two years.”

The importance of appropriate conditions to store food

Finally, the study “An inside look at the silo-bag system”, (Bartosik, 2012), evaluated the method of silage bags to store food and the quality of this storage system.

In this case, the study highlights the importance of having the appropriate conditions to store food in the silage bags. “The general results indicate that the dry grain (equilibrium relative humidity below 67%) can be stored in a silage bag for more than six months without losing quality. If the moisture content of the grain increases, commercial quality could remain the same for a maximum of six months in winter to less than three months in summer. In all cases, maintaining the air-tightness of the bag is a key factor for successful storage.”

This shows that the silage bags are an effective storage method for disease control of fungi and insects, but on the other hand, a more economical system compared to steel silage, that are more flexible, and offer possibilities to harvest more efficiently among other benefits.

Frequently asked questions about grain storage solutions using silo bags

Why is it essential to have solutions for grain storage?

The reasons are diverse and will depend on the specific needs of each farmer, his marketing approach and volume of the harvest. Once the grains are harvested, it’s necessary to store them immediately in suitable places using the best methods so that they retain their properties longer before they are marketed. Basically, grains are stored in fixed structures (steel/concrete silos) or in temporary containment (grain bags).

When the harvesting process is done on-field, immediate filling of the grain bags connected to the collecting machinery is possible, so you guarantee greater durability of the grains, a faster harvest, and a significant reduction in transportation and labour costs, thus ensuring safer commercial operations.

Another good reason to use temporary storage on-field (grain bags) is that there’s unlimited storage capacity, so if the harvest season exceeded your expectations, there’s a greater chance of stockpiling more food than expected, as long as space is available. In the case of grains, these can also be stored by quality-type-date to have better control over the seasons, prices and market fluctuations.

If something happens with one of the bags, for example, because the humidity levels in the environment increase considerably and unexpectedly, there’s no risk of contamination spreading to the other bags, so the rest of the volume will be in perfect condition.

The key is for good compacting of the bag when filling and make sure that the grains are as dry as possible to minimize the risk of excessive moisture so you can store them for more months without the food losing quality.

When these grain storage solutions are applied temporarily, implementation or start-up costs are minimized, compared to long term alternatives such as cement or metal silos. These fixed structures require investment in land, building permits, maintenance and financing the structures.

Other frequently asked questions

Usually, doubts arise when you’re looking for the best solutions for grain storage, especially with so many fluctuations in climate as well as the international grain markets and politics. Being aware of that, a webinar was held to talk about temporary solutions for grain storage as an alternative for times of market uncertainty and financial stress for farmers.

In the webinar, led by Daniel Fiersbach and Petras Diciunas, members of the export sales area of Armando Alvarez Group, several questions arose that we share with you below:

Temporary Grain Storage Solutions for Secure Business Operations

Are grain bags compatible with traditional grain elevator operators?

Yes, they are compatible. It’s common to encounter these grain operators in several countries; some don’t have enough storage capacity to reach 100% after the harvest season is over, so they make up the shortfall on storage by using grain bags as a temporary solution.

With the grain bags, most grain elevators also see the possibility to grow their business as they can expando on much more volume in the region with incurring in high structural costs.

Does a smaller grain bag guarantee better compaction than those with larger diameters, or is it just a matter of filling?

It’s a matter of filling-compacting and it depends to a large extent on what type of grains are being harvested or how big the harvest is. Usually, one of the two variables is used to choose the diameter, which makes this system so flexible and in the case of a smaller harvest, it’s recommended to use a smaller diameter. If the harvest is larger or the grain size is bigger, a larger bag should be used.

There are two types of bags, the largest ranging from more than eight or nine feet in diameter, while the smaller ones range from more than five or six feet in diameter. The bagging machines available on the market are designed for a specific range of bag diameters so it is important to be sure that the bag’s mouth fits on the machine.

Are grain bags recyclable?

Yes, they are since this is a PLD (Primary Land Development), which is an international recycling code, indicating that these bags shouldn’t represent a problem for the environment and can be recycled. Some people do that work and make money from it.

It should be remembered that agriculture handles a variety of processes that are essential to carry out all the tasks of cultivation and harvesting. In the case of the proper management of organic waste left after the harvest and food selection, many farmers use silo bags for composting.

Is the machinery the same for grain storage or silage?

Yes and no, it will depend on the task you are performing and the product you are going to use. Sometimes you use the same machinery by removing some of the parts and sometimes you don’t, but it’ll depend on what is being stored and the final use or purpose given to the silage.

Do most bag manufacturers use 7-layer technology or are those only used in specific cases?

There are only a handful of bag manufacturers that can manufacture a 7 layer grain bag since this technology is quite recent. This enables the manufacturer a better product formula design as well as enhanced mechanical properties.

Will manufacturers create a bag with repellent for birds and other wild animals? It’s the main complaint we hear

This type of bag has been tested; we hope to have an option to order these bags for the next season. Regarding the costs, we still have to see the results, we don’t want to present a product that is not ready for the market, so it’s too early to talk about prices, but once it’s ready we’ll certainly have a real offer.

Do you put any recycled material in the grain bag?

No, for two reasons. The first reason is that there are some markets where you need a specific certificate for contact with food, so it’s not possible to use any recycled material. And the other reason is that this is a product where you need a lot of homogeneous quality (mechanicals and UV) because we are talking about storing high value produce, about 250 euros per ton, with 200 tons you can already calculate the value of this material. Only a premium bag can guarantee proper containment on-field and protection of the grain quality.

What would you say is the worldwide percentage of bagged grain storage compared to silage?

There is no certainty of the exact percentage, it depends on the market and the year. Bags are still a new and growing technology, compared to traditional concrete and steel silos. Grains are mostly stored in bags, compared to silage, perhaps in a ratio of 80 percent grains vs 20 percent silage, but this is only an estimate made based on Daniel and Petras’ experience in the market. It will depend on the area. In Central Europe, silage bags are more frequently used, but surely in Latin America or even in Ukraine, Russia is more useful for grain storage.

Temporary grain solutions using silobags

Is it usual to store in silo bags?

It will depend on the area. To get an idea, Argentina estimates that will use 450,000 bags this year, where it’s very common to do so. However, in countries like Germany, it is not a common practice, so it’ll depend a great deal on the area where you’re located and the infrastructure you have.

In eastern countries, they take advantage of their big old concrete silos. They seem to be indestructible and could stand for the next century. However, they also use silo bags to add storage capacity since their harvest is larger than 20 or 30 years ago, due to new technologies, new seeds, new fertilizers, etc.

Is it possible to store cereals for human consumption in silo bags?

Yes, it’s possible. Although there are no special bags to store grains or food that will be used specifically for human consumption, there’s a special certification for food contact.

Silo bags are an excellent tool for large food processing companies to take advantage of low-priced grains and have additional temporary storage.

Can the bags thicknesses vary in microns by size of diameter?

During the manufacturing process of the bags it is possible to have fluctuations in the thickness of the plastic. Due to the seven-layer technology the variation is being reduced to a minimum. So, if we compare the smallest bag with the larger ones, there shouldn’t be more than 10% to 15% variation from nominal thickness, whereas with the three-layer bags these percentages can go up to 30%.

From the point of view of the bag quality, are there differences in grain bags produced by different manufacturers?

Yes, each manufacturer has its technology, product formulas and specialty raw materials, but it depends also on the farmer and his bagging techniques. If you’re an experienced user, you’ll be able to compensate for some drops or failures of the bags, but there are certainly different qualities in the bags. There have been very different results depending on three, five and seven-layer technology, so not everybody has an equal product.

How do you determine the thickness of the bag you’ll need?

You have to know what is going to be stored in the bag, whether it is grain, silage or something different like salt, chemicals, sawdust or compost. Being clear about the final objective will define the thickness because the material itself is different, the tensions, stresses and the bag is different for each product, that’s how the thickness is defined.

How can we protect the bags from rodents and birds?

There are two types of protection: mechanical and chemical. The mechanical protection contemplates cleaning the space where the bags are stored, using the protective net and covering the bag as much as possible. The chemical protection has to do with the manufacturing process that incorporates special additives to the plastic. These additives can be for smell or taste. In any case, the most recommended option is to keep the storage space clean.

Does the system need cooling?

In general terms, no, it will depend on the type of grain you are going to harvest and store. In some cases, cooling is used to prevent condensation if the grain is very hot when harvested. However, usually, the inside of the bag has a temperature similar to the outside temperature, so it is not necessary to add any special cooling.

In other cases, cooling is used for pest control, causing the metabolism of pathogens to decrease. It is not something so necessary, since the oxygen that’s inside the bag is consumed very quickly and new oxygen can hardly enter the bag, so insects also die.

To learn more about this topic, we recommend watching our webinar on temporary solutions for grain storage.