by Rebecca Sherratt, Features Editor, Milling and Grain


The demand for sustainable feed and food production continues to grow as the human population rapidly increases, and as a result of this the correct storage of raw materials and feed becomes only more crucial in the bid to reduce waste. We have discussed before, in Milling and Grain, various methods to correctly store your raw materials, the best solutions to choose and how to implement proper storage systems, but another issue is also the notoriously difficult task of cleaning your silo or grain bin. How exactly is the best way to ensure your solutions and products remain sanitised and hygienic?

There are a variety of reasons why it is crucial to correctly empty and sanitise your storage solutions, ranging from the threats of insects, mycotoxins, damp and material build-up.

Combatting the damp: Aeration is key

Clean, dry materials are essential for high quality final products. If your raw materials such as grain, soybeans etc are not dried adequately, damp can spread throughout the silo and cause tremendous damage. Fine particles can restrict airflow through the grain mass and make it difficult to thoroughly dry the raw materials within the silo, as well as regulate temperatures.

To minimise risk of particles preventing proper airflow, broken kernels, fines and undesirables should be removed from the bulk materials to increase the quality of the stored product. If silos and bins cannot easily be screened, then professionals recommend removing smaller loads of grain, one section at a time, to check through in stages. Whilst this solution might not be the speediest, it proves to be an effective and thorough solution.

Between 14 and 15 percent moisture content is considered the sweet spot when analysing moisture content within raw materials. At this level, the moisture balance prevents the risk of mould growth, but is not too low that farmers may spend a significant sum of their budget keeping their harvest drier than is required.

Combatting insect and rodent infestations: Conducting thorough cleans

Insects are potentially one of the biggest issues when dealing with storage solutions. Removing infestations is rarely a simple process, as infected equipment and harvests can transfer over to seemingly clean harvests and other materials.

Traces of old grain and other raw materials must be removed from combines, truck beds, augers, grain carts and other products used in the storage process. New grain must, under no circumstances, ever be placed on top of older grain within a silo or grain bin, as this can lead to further infestation.

Insects cannot live on extremely dry grain (dry grain being grain with 10% or less moisture content), so there are other benefits to keeping your materials dry. As they are cold-blooded, grain insects become inactive at temperatures any lower than 13°C (55°F).

There is also the threat of mice and rats contaminating raw materials and feed, which can be prevented through several different methods. Mice and rats are privy to burrowing underneath silo and bin foundations, so the outside of your storage solution must mitigate this risk. Tall weeds surrounding your silo must be removed and the surroundings of silos must be analysed to ensure water drains away from the bin foundations.

Combatting the risk of mycotoxins and mould: Implement microbial inoculants

The risk of mycotoxins is one that can start before the storage process and needs careful monitoring throughout the entire harvesting production chain. Steps must be taken to prevent fungal growth pre-harvest as well as after ensiling. In a study conducted in 2010 by Dragan R Milicevic, indirect costs concerning quality control measures regarding fungal contamination exceeded $1 billion per annum in the US alone.

The threat of mycotoxins in silage relates again to the two previous points mentioned earlier: damp and insect infestation. Unhealthy levels of damp and insects in silage both cause potential for moulds and toxins to grow in silage. Moulds can grow at between 10-40°C (50-104°F) and between pH's 4-8. Delayed harvesting, damaged packaging or broken silo covers can also cause mould to take form.

When first filling your silo with harvested materials, the risk of moulds can be minimised by ensuring to harvest at the recommended dry matter (DM) concentration and silos should be filled as quickly as possible, tightly packed to achieve the recommended density. Most atypical silage moulds, such as Fusarium, Monascus, Rhizopus and Aspergillus cannot flourish in low-oxygen environments and so the real risk areas for contamination within a silo are the top layer of materials and the shoulders of silos, more prone to oxygen infiltration.

One particularly effective solution when protecting stored materials at risk within a silo is the use of mould-inhibiting chemical additives or microbial inoculants. The implementation of lactic acid bacteria has been well documented in its role towards reducing fungal growth in silage.

Following several in vitro studies, Lactobacillus brevis and Lactobacillus plantarum were proven to reduce ochratoxin content by between 16-35 percent (Piotrowska, 2014). In 2017, Martinez-Tuppia also conducted a study on ensiled high-moisture corn that, through the use of L. brevis, degraded fumonisin B1 into its hydrolysed metabolite. The same effects have been exhibited with Lactobacillus paracasei towards vomitoxin (DON).

Combatting material build-up: Employ professional clean-up teams

Eradicating silo build-up is very beneficial, not just from a hygiene perspective, but also financially. Removing material build-up frees up lost space in your silo, so more space is available for your fresh produce.

Before engaging in silo cleaning, first ensure that there is a path for the cleared material to easily leave the silo to be disposed of. The discharge opening in the silo must be clear and a conveyor, truck or other takeaway mechanism must be ready to receive materials. When cleaning the top of a silo, the undercutting technique is commonly implemented. This involves working from the bottom of the accumulation upwards, whereby the waste is pulled out from under its own weight.

The standard team when cleaning silos consists of three people, with an entry technician being winched into the chamber. The second member of the team manages the winch whilst the third member records gas readings and is present to assist in case of an emergency. A gas detector must always be used before entering the silo to test the air, as oxygen deficient silos are considered too dangerous to work within. It is recommended to hire a specialist team to clean your silo, who are trained in conducting themselves in confined spaces, familiar with the protocol in case of emergencies and able to use the equipment effectively and responsibly.

A myriad of options

Whilst such a wide variety of issues can seem daunting at first, experienced silo managers will know that once the relevant safety and hygiene protocols are put into place, they are easy to maintain and contribute greatly to maintaining healthy, profitable harvests. Conduct your own research and discover which solutions are the best for you and your solutions.

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