“The Food and Agriculture Organization (FAO) estimates that one third of the food produced globally for human consumption is lost or wasted along the supply chain. Every year, million tons of grain is lost due to improper storage conditions.”
Grain began being cultivated in the Neolithic, and the Sumerians became the first society to store it by ca. 4000 B.C. Grain represents the most important nutritional element, both for humans and animals. Its storage is especially important to guarantee food safety, but also for price stability.
The Food and Agriculture Organization estimates that one third of the food produced globally for human consumption is lost or wasted along the supply chain. Every year, million tons of grain is lost due to improper storage conditions. Factors like humidity, heat, pests and aeration which are effective on storage conditions affect the quality and quantity of grain and shorten the storage period. In this regard, proper storage techniques are among the most important elements in food supply chain of grain which is a significant nutritional source.
Thanks to the possibility to be stored for long-term, grains have long been to the rescue of mankind in time of drought, famine and war for centuries. At a time of continued population growth, the need for food sources increases steadily and yet agricultural areas and production is limited. Thus, food waste becomes rather unaffordable – and here is where grain storage and storage conditions are become critical: when proper storage conditions are provided, loss and spoilage in grains might be reduced greatly.
In some countries, food losses are estimated to range from 15 to as high 50% because of bad/inefficient storage. This is especially problematic in developing countries where food security and access are a real problem. The causes for such waste are manifold: harvesting at an incorrect stage of produce maturity, excessive exposure to rain, drought or extremes of temperature, contamination by micro-organisms and physical damage that reduces the value of the product.
Food losses contribute to high food prices by removing part of the supply from the market. They also have an impact on environmental degradation and climate change as land, water, human labor and non-renewable resources such as fertilizer and energy are used to produce, process, handle and transport food that no one consumes.
It is here when postharvest management plays a major role. It includes all elements in the value chain, from field production to the kitchen and consumption. Among the activities in postharvest management you can count with harvesting, handling, storage, processing, packaging, transportation and marketing.
WAYS OF STORING GRAIN
There are a myriad of grain storing techniques: from brick and mortar warehouses, to concrete silos or silo bags. However, for considerable quantities and industrial purposes, metallic silos have proven to be the most versatile and economic mid-and-long-term solution.
Bulk against Silo Bags: In terms of management, bulks allow for a large volume of grain using mechanical transfer an automatic unloading, at speeds of up to 2.000 ton/h. Transport and handling is much faster even in port or airport installations, while bags are not allowed large volumes. It is also less labor intensive than bags.
The advantages of metallic silos over brick and mortar warehouses are greater too. Metallic silo can store larger amounts of grain using a more limited space than warehouses. In addition, metallic silos allow for a total automation, which translates into lower investments and operational costs per stored tons.
Metallic silo against Concrete Silo: The two operate following the same principles and techniques, and can be equipped with pretty much the same elements; however the investor will soon realize that a concrete silo will make for a slow and difficult installation, with higher maintenance and investment needs.
In summary, in the grains and bulks logistics industry, metallic silos become the top investor-friendly asset thanks to these advantages:
• Great storing capacity in a space –saving solution, from 20 m³ up 25,000 m³, approx. 18,750 tons.
• Economical, easy-assembly and easy-maintenance. Less investment required in civil works and maintenance is almost non-existing.
• Better post-harvest management for less losses and quality improvements, due to humidity control, temperature control and ventilation.
• Effective protection against weather, rodents and insects.
• Long storage periods allowed.
• Automatic loading and unloading.
• High handling speed and transport capacity, increasing port installations improvement.
• Bulk handling materials allowed.
• Less cost and more capacity.
• Less labor cost and resources.
Definitely, storing in metallic silos improves correct grain preservation. Yet, the work has just started, as the manager should consider some other factors that require management for successful grain storage: These are temperature, humidity and insects, which are in turn intertwined. Steel silos were developed alongside with the mechanisms to manage these factors, as a valid and proven option effective in protecting stored grains, while underpinning protection from pests, improving food security, empowering smallholder farmers, enhancing income opportunities and job creation, and safeguarding the agro-ecosystems.
Generation of organisms: pests are one of the main threats to stored grains, and these depend on a large extent on humidity and temperature. To this, ventilation has become the main tool to defend your grains. It requires a multifaceted approach to management, as it requires a modulation between humidity and temperature both inside and outside of the silo. A sound ventilation system will attain the right conditions of temperature and humidity for the grain considering the conditions outside of the silo.
To put it simply, ventilation brings air form the outside, with the right moisture and temperature conditions, to keep and maintain the grain inside to our target of humidity and temperature for long term storage.
Working at unison with ventilation, a temperature monitoring system allows for the control of the temperature over stored material and storing conditions. A system of probes inside of the silo provides timely readings of temperature and, in some cases, moisture, across the silo grain column. It is a passive system, which requires no maintenance. The probes can be replaced without emptying the silo, and are supported on two beams avoiding tensions in the roof.
Symaga offers an aeration system to meet customer requirements and cover all their grain storage needs:
Aeration Roof Vent with circular design preventing the accumulation of water, snow and rubbish and opposes less air resistance. It is easy-assembly, embossed, perfect-sealed with the roof section, and it comes with anti-bird net. It is prepared with a special sealing system for fumigation, and ready for the installation of an exhaust fan coil to avoid condensation. Extractor fans embedded on the vents of the roof also work as part of an aeration system, removing out of the silo the air with potential of condensation.
Central to the aeration system are the different aeration channels made up of foundation channels that are covered with special galvanized boxes, corrugated and multi-perforated covering between the 25% and the 30% of silo bottom. Channels come in different shapes, commonly known as “Y”, “H”, “C” if silo is conical concrete bottom, or “T” if it is a hopper silo.
Fully Perforated floor: The fully perforated floor is supported by a floor galvanized steel structure. Perforations are of a diameter of 1 or 1.5 mm, depending on the stored grain. Brackets are made of hot dip galvanized steel, which allows a better airflow and therefore better ventilation.
Prefabricated gutter: Gutters are installed in silo foundation. This element is manufactured in 3 mm thickness galvanized steel, depending on installation characteristics (size, width and depth of the silo and foundation, and the total volume of the stored grain). “Y”, “H” and “C” types available.
A key element in every ventilation system is the fans in charge to move the air around. In Symaga, our fans have IE2 certification, ensuring energy efficiency.
Hopper aeration: Aeration cannel system with drillings, fixed to a Hopper sector and prepared for connection with the fan.
Ventilated cone: Elevated cone made of galvanized steel inside the silo. The system avoids contact between the ground and grain, making civil works cheaper.
Grain chiller: Improve grain preservation, avoiding fumigation. Minimize weight loss. Allows cooling regardless of environmental conditions.
Symaga silo is manufactured in galvanized corrugated steel, with a minimum 600 gr/m² coating for all elements, but for the roofs, protected with ZM310 gr/m² steel sheets, ensuring a double service life more than other suppliers..
Steel galvanization (cover it with a cap of zinc to protect it from the corrosion) is a common practice to protect the pieces of steel that are going to be exposed to adverse environmental conditions for a long time.
Legs and bracing of our structural steel silos are hot-dip galvanized. Hot dip galvanizing process in a bath of molten zinc (or zinc – aluminum – magnesium)*. Steel coils are unrolled and prepared in three different phases: degreasing, pickling and fluxing. Steel coils are preheated to 600 – 650ºC and heated to 750 – 850 ºC getting dry in a protective atmosphere (N2, H2). Hereafter coils are immersed in a bath of zinc* to 450-500 ºC, being dried in an air flow to adjust the thickness.
Hot dip galvanization by immersion in a bath of zinc is normally used with pieces which don’t accept the continuous process, as welding components or superior thickness. The process is more of an artisan approach, and doesn’t guarantee thickness homogeneity in components.
SILO DESIGN AND CALCULATIONS
The versatility of our silos makes them available for different industries such as breweries, animal feed, port facilities, our mills, ethanol, drying, our mills, and storage of raw materials for the plastic industry and biofuels.
The growing product line allows us to offer a storage system that fully meets the needs of our customers by offering silos from 5 m³ to 25,000 m³ capacity. In order to do the design and calculations of the silo it is necessary to know the type of grain, use and location.
Out technical team designs silos considering all internal and external elements that affect it soundness. The internal are: grain load, angle of repose, specific weight, internal friction, specific weight excluding grain and security coefficient. Our technical department calculates our silos with a density calculation of ρ = 834 kg/m3* and our security coefficient calculations is over regulations. Under requirement, we calculate in any other code (Eurocode, NPF, Gost, etc). Also, the external factors play a big role – seismic coefficients, wind loads reinforces and snow will require certain modifications to make your facility a safe working space.
The silo is a central part for safe and caring grain storage, but it needs an operation and general maintenance that starts from the first load of grain. You must check temperature and moisture content of the cereal being loaded into the silo and check the temperature of the stored crop at regular intervals & aerate as necessary. You should follow strictly the first filling procedures (especially center load). And after discharging the silo completely and after isolating the sweep auger, clean the inside of the silo thoroughly, including under the aeration grids to minimize the risk of infestation.
Projects delivered in over 145 countries, 42 million m³ built, 10,000 projects, 35 years of experience, the integration of our silos in the biggest storage projects; these facts consolidate Symaga as a major reliable manufacturer in the industrial silo sector. Tailored technical support to each project and state–of-the-art facilities make Symaga your best partner for storage.
About Alfonso Garrido Parejo
Experienced Logistics Manager and Sales Director with expertise leading successful Business Development around the world. Passionate about the acquisition of new business partners and clients.
He is an economist with more than ten years of international experience in business and international development. Currently he is am working as a CEO at Symaga Silos, European Leader and worldwide recognized company in the grain and storage sector