Grain storage and protection are essential for the grain producers, traders and processing industry. They assure good quality of the grain as well as availability of grain as food and raw material. It is mandatory for all involved groups to take best practice to avoid deterioration and losses because any grain matters.
GRAIN STORAGE
Grain storage is essential for preserving the harvest after it is reaped until it is ready for consumption or processing. It helps bridge the gap between harvest seasons and allows farmers to store surplus grain during abundant years, ensuring a steady supply during lean periods. Proper grain storage not only ensures food availability but also helps maintain the nutritional quality and safety of grains.
There are two systems of grain storage applied according to the scale of bulk. Bag storage is used common in small-scale farming. Grains are stored in sturdy bags made from materials that protect against pests and environmental conditions. Bag storage is more labor-intensive and less efficient for large volumes. The state-of-the-art grain storage practice is bulk Storage. Large quantities of grain are stored in dedicated facilities like warehouses, silos or grain bins. This method is efficient, cost-effective, and suitable for both farmers, commercial grain handling and mandatory for grain processing industries.
The core part of the bulk storage facility is the storage structure designed as warehouse for flat storage or as silo or grain bin as vertical facility. Both are usually mechanized to allow an easy grain handling. That is a critical process that involves the efficient loading, unloading, and movement of large quantities of grains within the storage facility. It helps prevent damage, contamination, and spoilage, preserving the nutritional value and overall quality of the stored grains. Effective handling techniques reduce physical losses during transportation and loading/unloading processes, minimizing financial losses. Streamlined processes ensure timely movement and distribution of grains, contributing to an efficient supply chain. Last but not least, the safety of the handling practices is crucial to prevent accidents, injuries, and potential hazards during loading, unloading, and storage activities.
Taking a further look at the storage structure it is focused on the silo as most common and standardized system of modern infrastructure for grain storage. It offers a high storage capacity, efficiently utilizing vertical space, which is particularly beneficial in areas with limited land availability. If the silos system is properly designed, it does provide optimal conditions, such as controlled temperature, humidity, and ventilation, which help preserve the quality and nutritional value of stored grains. Its main function is to protect grains from pests, rodents, and environmental factors.
Establishing grain silos can be capital-intensive, making it challenging for small-scale farmers and underdeveloped regions to invest in this infrastructure. Regular maintenance and occasional repairs are necessary to ensure the integrity of the silo structure and its proper functionality. Improper grain management can increase that effort tremendously. Silo-related accidents, such as grain entrapment and structural failures, can pose significant safety hazards for workers and require stringent safety protocols. Extreme weather events, like storms or floods, can damage grain silos and compromise the stored grain’s quality. In addition the seismic zoning determines the way of construction and foundation.
Nowadays there are more consideration about bulk storage in silos which give essential potential to improve its operation. There are the integration of advanced climate control systems and environmental sensors to ensure optimal storage conditions, reducing spoilage and material loss to support the grain management. State-of-the-art security systems, such as biometrics and surveillance to safeguard bulk storage facilities and materials to protect from theft and unauthorized access. Important is to provide training to employees and ensuring compliance with storage regulations to improve handling practices and to reduce the risk of accidents or contamination. Another new important field is developing bulk storage facilities using sustainable construction materials and design principles that promote eco-friendly storage practices.
All in all the storage system needs to be managed properly to assure its function and the safety of the grain. However, the grain protection requires more than just a container which is loaded and unloaded. Therefore, grain protection is the essential way to keep grain’s quantity and quality at best.
Several constrains affect the grain by its nature or by the condition of storage. It is often underestimated that grain is a biological active commodity which changes over the storage time as well as affects the storage condition. Aside of this proper moisture content for storage and purity of the grain is important. In addition proper temperature and relative humidity are a concern for crop protection, but usual brought up by the ambient condition at the location and the seasons. Additional constrains come up by post-harvest threads like birds, rodents, weevils, microbes and fungi. All can be taken care if proper grain management is applied and conducted. The various grain management techniques must be carefully selected. The way of their application as well as their limitation needs to be understood to avoid failures and grain loss.
CONSTRAIN OF GRAIN STORAGE
The self-sustaining chemical reaction of grain causes that dry matter of the grain is transformed into heat and water which is often described as hot spot at a storage. Grain continues to respire after being harvested and causes losses of weight. However the generated heat bears the risk of fire at a grain stock and must be managed properly to protect it. The rate of the activity is dependent on the grain’s moisture content and temperature. Respiration becomes exponentially intensive as the temperature and moisture content of grain increase. Loss of grain quantity by respiration may be as high as 0.5 to 3 % according to the temperature and moisture content of the grain during the storage.
Management of grain’s moisture content and its temperature are the only ways to avoid losses and danger. If it is neglected additional risks by infestation of bacteria, mites, insects and fungi are developed. Other consequence are grain damages by water condensation inside a storage which leads to caking of grain.
During storage the highest risk is the infestation of insects. More than 80% of the postharvest losses are caused by weevils as stated by FAO. Each grain has a specific dominate weevil with the nature to attack that grain preferably. The growth rate of insects is exponential at the optimal condition of their environment. A main driver for their nature is the right temperature. Favorable temperature levels according to their nature will lead to optimal development with most damage to the grain. Any lower or high temperature affect their lifecycle by reducing the fertility as well as the time of their lifecycle. At low temperatures they will fall into hibernation and stop their affecting the grain.
The damage of the grain is mainly the mass loss by consuming the grain and the nesting inside the grain kernel. In addition there is the risk of a contamination by excrements and bacteria. It is absolutely necessary to monitor insects and act with serious grain management about it.
A third main danger for grain storage is the development of fungi which depends on the temperature, the relative humidity and the grain’s moisture content. Grain of more than 14% moisture content create fungal development at the right temperature because the level of relative humidity is high enough to allow their growth.
Thereby the danger of fungal contamination is not only the deterioration of the grain but the increase of mycotoxin which affect the health of human and animals. Proper grain protection is important and must be considered mainly by managing the proper moisture content of the crop in combination with right temperature level if the acceptable moisture content can’t be assured or maintained. It is important to consider that respiration causes rise of water by reduction of grain’s dry matter leading to higher moisture content by the nature of grain.
GRAIN MANAGEMENT AND PROTECTION
Some management techniques are covered up here to understand what they contribute to grain protection. It must be assumed that the grain which is stored has been harvested at the proper maturity and moisture content.
Since pest is one of the main problems of grain storage and number one concern of grain protection, the setup of the grain storage is essential. Therefore the exclusion strategy is used in pest control which refers to the practice of preventing pests from entering a grain storage. Exclusion techniques can involve the use of physical barriers, such as screens, seals, and caulk to close gaps and cracks that pests could use as entryways. The idea behind exclusion is to deny pests access to the interior of storage, reducing the need for pesticide use and helping to prevent infestations from occurring in the first place. It is an essential component of integrated pest management, a sustainable and environmental-friendly approach to pest control that aims to minimize the reliance on chemical treatments and focus on prevention and non-toxic solutions.
If moisture content of the grain is too high, it is mandatory to apply a drying according to the followed grain management and under consideration of the targeted storage time. It is by far too much to cover that topic here which will be described another time. Even if drying is required, cleaning of the grain is the essential step performed ahead.
Cleaning of the grain from dust, chaff, broken or unripe kernels, impurities and dirt is always required as a grain bulk bring all along. Those do occupy space of the costly storage and add risk to the storage of grain by their moisture or contamination property. There are different cleaning technologies available which act according to the physical property of the difference between good grain and unwanted material. The cleaning capacity must be considered to match with the volume of the incoming grain to avoid delays. A proper setup of the machinery and monitoring of its operation is required. Uniform grain with limited moisture variation and without unwanted materials optimize the storage condition and maximize the storage volume and leads to a good base for grain protection.
During the loading of the grain the bulk forms an angle of repose at the top by the natural property of the grain. These irregular surfaces can lead to several issues and decrease the storage capacity. It is essential to understand that the uneven shape affects the protection of the grain by creating an uneven flow of air through the bulk when aeration is applied. It is known that the air flow will escape at the lowest point of the bulk by taking the easiest way through the bulk. That develops the risk that certain areas of the grain remain untreated, and it is required to level the grain bulk. The process of grain leveling involves using specialized equipment, such as grain spreaders or leveling augers, to distribute the grains evenly across the storage area. By unloading a certain quantity of grain the uneven shape at the top is halved of its height which does ease the leveling. In addition it cores segregated light materials at the center of the silo which affects an air flow as well.
It is essential to monitor the grain during the storage. Then the condition of the grain is clear and if a change takes place a proper action is possible to protect the grain. The most common monitoring is to measure the temperature inside a grain bulk. It observes the condition of the grain as its respiration or activity by insects and molds are indicated by an increase of the bulk temperature. The hot spots are identified by a three-dimensional grid of measurements points and allow a risk management accordingly. If cables with probes are used it is mandatory to fix the cables at the ground to avoid its movement by the loaded grain and misplace the cable. Those systems may be equipped with additional relative humidity and CO2 sensors and use data record and analysis system for and automated alert. Only if the condition of the grain is known a proper protection is possible and the right application for grain management techniques is possible.
A minimum of grain protection is applied by aeration. It involves the controlled movement of ambient air through the stored grain mass. Aeration systems typically consist of ducts or perforated pipes installed within the grain mass. These ducts or pipes are connected to a fan or blower located outside the storage structure. When the aeration system is activated, the fan draws outside air into the ducts or pipes and then pushes it through aeration screened canals or full perforated floors into the grain mass. At the exit of the air flow are vents or exhaust fans which are opened or activated during the operation. The particular design and dimensions of the aeration system are supplied by the designer of the bulk storage.
Aeration helps to control the temperature of the grain mass. During storage, temperature fluctuations can occur due to external climate changes, but mainly by the natural respiration process of the grains or the activity of weevils and molds. If the temperature rises too much, a risk of fire is developed. By forcing air through the grain, aeration dissipates excess heat and maintain a more consistent temperature throughout the storage period. Usually aeration is very effective if cold and dry air is available. It may be critical to use aeration when the outside air is hot and humid as it may boost the respiration of the grain or lead to moisture increase. It is advised that the temperature of the applied air is at least 7 Kelvin lower than the grain’s temperature to avoid issues. Therefore the application of the aeration is weather dependent. However in any case it must be operated if the rise of the grain’s temperature is crucial to avoid a risk of fire. Aeration may lead to a reduction of grain’s moisture content up to 3%. Thereby it should be understood that aside of the water also the dry matter loss by respiration takes place as mentioned above.
One of the most applied grain protection techniques is fumigation. Fumigation of grain is a pest control method used to eliminate or control insect infestations and other pests in stored grains. It involves the application of fumigants, which are gaseous chemicals with pesticidal properties, to the grain mass inside a storage facility, such as a silo, grain bin, or warehouse. Fumigation is typically used as a last resort when other pest management strategies have proven ineffective or when infestations are severe. It should not be used as a routine treatment to solve infestation risk. The target of fumigation must be to stop the infestation of insects totally. A failure will create resistant insect population. The success of fumigation is determined by the selection of the right chemical according to the infectious species of insects, by applying a constant and effective concentration during a sufficient time at the right ambient condition. A proper management by professional and qualified staff is mandatory. A minimum of two persons act as team to assure labor safety. The procedure must be applied strictly according to the specification as fumigants are dangerous by their toxicity.
The application procedure starts with the evaluation of the threshold level for the specific insect by proper monitoring throughout the storage. If it is reached the right fumigant must be chosen according to the way of application and he ambient conditions. The storage must be airtightly sealed to assure the effectiveness. The test of the airtightness is essential and usually performed by a pressure test. The area must be locked and marked. The gas is applied until the effective concentration is achieved. The concentration must be monitored during the treatment. Fumigant is added if the concentration reduces to maintain the effectiveness. The duration of the fumigation is according to the specification to reach 100% kill of adults, larvae and eggs. If ambient condition change, the application must be adjusted. After the effective time did pass, the storage is to ventilate sufficiently. A quarantine period of the grain is to consider before the grain can be used or sold.
Controlled atmosphere (CA) storage of grain involves modifying the composition of the air surrounding the stored grains to create specific conditions that can extend the storage life and preserve the quality of the grains. The two most common gases used in controlled atmosphere grain storage are nitrogen (N2) and carbon dioxide (CO2).
The grain protection by controlled atmosphere is similar to fumigation but less risky for the user and the environment. Thereby either nitrogen or carbon dioxide are applied to the required level. The nitrogen is an inert gas, which means it does not react chemically with the grains or support the growth of insects, molds, or microorganisms. Carbon dioxide is a naturally occurring gas that is produced during the respiration of grains and other organic materials. Both are applied to their specific and required concentration to achieve effectiveness. Therefore a special storage facility is required as well as specialized equipment and monitoring systems to maintain the desired gas composition accurately. Additionally, the specific gas composition and storage parameters may vary depending on the type of grain being stored and the storage duration. Proper monitoring and management are necessary to ensure the effectiveness and safety of controlled atmosphere storage. While nitrogen needs a concentration of at least 99%. Carbon dioxide is applied with concentration of 30% to 80%. Both are mainly used to protect the grain from insects as well as from molds and lower the respiration of grain by reduced oxygen level. High carbon dioxide levels in combination with water (condensation) may create carbonic acid inside the storage which is critical for the grain quality as well as the infrastructure. The application of the gas is done after the storage is fully loaded and sealed. If grain is unloaded the preserving stage ended as fresh air flows into the storage usually. Therefore it is only used for silos which store the grain for a certain time, but useless for silos which are loaded and unloaded because of the processing operation.
Grain cooling is a post-harvest practice in agriculture that involves reducing the temperature of freshly harvested grains to a safe and optimal level for storage. It is an essential step to preserve the quality of grains and prevent spoilage during storage. Grain cooling is particularly crucial in regions with warm climates or when grains are harvested at high temperatures, as heat can accelerate the deterioration of grains by respiration and promote the growth of pests and molds. Further water condensation inside a bulk storage is prevented at any time if grain cooling took place. The specific cooling requirements for different grains may vary depending on factors such as grain type, initial temperature, ambient temperature, humidity, and storage duration. It’s essential to monitor and manage the cooling process carefully to achieve the desired storage conditions and preserve grain quality effectively. If the ambient are not in favorite to use outside air, the grain cooling must be performed by a grain cooler.
The technology operates with a mechanical cooling process constantly providing cold and dehydrated air completely weather independent. The grain cooler is connected to the grain storage and the conditioned air is blown into the grain bulk. The air flow passes the grain and removes the heat of the grain. The heated air exits the storage. The grain cooling continues until the entire bulk is cooled to the desired temperature which is in general at a range of 10 to 18°C. Then the grain cooler is turned off and the air inlet and vent openings at the roof are closed. The cooled grain is kept in the storage until unloading or refreshing of is required if the temperature may increase during storage. Usually the temperature is well maintained over a certain time as grain is a low heat conducting material and respiration activity of the grain is suppressed by the low temperature.
The grain cooling takes place already when the screen of the aeration system is covered by grain. It is continued until all grain has reached the safe level of low temperature. If grain is added the operation will start again which allows the grain protection even for silos which are regular loaded and unloaded. The mechanical grain cooler is moved from storage to storage, that reduces the required machinery to one of few units. As the processed is reliable controlled the air condition is constant. That allows to make use of the physic of air and the hygroscopic property of grain to achieve a moisture control of the grain or do intentionally a limited grain drying of up to 0.5 to 2% dependent on the initial moisture content of the grain. A retrofit of the grain cooler is always possible for storage system using a aeration system. Then only the blower of the aeration system must be removed to give space for the connection of the grain cooler. Further the technology can be moved from site to site according to the requirements of the seasons or the grain.
Grain storage and protection are essential for the grain producers, traders and processing industry. They assure good quality of the grain as well as availability of grain as food and raw material. It is mandatory for all involved groups to take best practice to avoid deterioration and losses because any grain matters.