Silo storage - The sky is the limit

Technological advances in both science
and construction methods mean that the sky – or rather the ground area where a dry bulk silo can be built – is literally the limit.


By Suzette Scheepers


Even in biblical times farmers were faced with the concern for feeding their livestock, and themselves, during the harsh winter months. Even then they considered the rise and fall of the seasons, the yin-yang effect of feast and famine, and they knew that they had to devise a plan to effectively store food and grains for use all year long.
     The challenge was to protect foodstuffs from blowing away in the wind, and spoiling because of the rain, it also had to be safely preserved away from insects and hungry scavenging animals such as rats, birds and snakes that would make an easy meal out of the stored food.
Enter the advent of the silo, from the Greek word ‘siros’ that means a ‘pit for holding grain’, one of the most efficient designs to see the light for grain and dry bulk storage and is still employed in most dry bulk storage facilities to this day.
     Silos are designed to stand tall and slender like a rocket fuselage. Its upright design has also meant that stored food could occupy space vertically rather than horizontally – using space optimally and allowing more farmland to be utilised for growing crops and grazing animals. By nature of its design it has also become much easier to dispense stored foodstuffs as material at the top of the silo is gravity fed down for easy access during dispensing.
     Contrary to a flat design, the rounded dome at the top of the storage silo not only reduces the horizontal space, but it also makes it a lot less likely for rain to accumulate. This impacts the integrity of the roofing design by reducing stress on the storage facility as well as decreasing the probability of roof leaks occurring and spoiling of foodstuffs.
     Today, more modernised silo designs are still built on the basics, but with the advent of solar or electrical powered ventilation systems that keep grains stored at certain temperature and humidity levels. The advent of electricity also brought about a number of other bulk silo uses, such as employing air conditioning and heated units to store a larger number of fruits and vegetables than ever before, such as coffees, apples, nuts, pineapples and many more.
     The introduction of raw materials management systems has meant a more effective way of storing flour. The result is that flour cost is reduced significantly as it may be delivered in bulk for a lot less than a bagged product. Take these materials management systems and couple them with water temperature controllers, and a much more consistent dough temperature and dough mix is the result that again ensures a more consistent, more profitable end product.
Silos are by no means a non-hazardous industry. The reality is that many people die annually in the process of filling, cleaning and maintenance of silos. Firstly, the operating equipment is dangerous, and secondly, just one slip on the ladder or platform may have severe consequences.
     Fires are also a common reality and may result from associated ducts and buildings exploding due to the air inside the silos becoming laden with finely granulated particles, such as grain dust. One spark from metal rubbing against a metal duct, or due to static electricity building up due to dust movement along ducts when conditions are extra dry, and explosion powerful enough to blow a concrete silo and adjacent buildings apart is the result. It normally also sets nearby grain and buildings alight.
     Silo cleaning also brings about its own set of challenges. The two main reasons for cleaning in dry-matter silos are bridging and rat-holing.
     Wikipedia describes rat-holing as material adhering to the silo sides, reducing its operational capacity and giving rise to cross-contamination of newer and older material. Bridging, on the other hand, is something that occurs when the material interlaces over the unloading mechanism at the base of the silo and blocks the flow of stored material by gravity into the unloading system.
     There are many ways to skin a cat… or clean silos, in this case. However, the 1990s introduced acoustic cleaning to the industry, a less risky, non-invasive and very cost-effective way of keeping small particle silos clean.
     Looking at the state of the silo industry in South Africa, then it is clear that the deregulation of agro industries in South Africa in 1997 impacted significantly on the logistic of local grain storage systems and how they function today.
     The Baker previously noted that grain is traded by way of the Johannesburg Stock Exchanges’ (JSE) South African Futures Exchange (SAFEX) platform as a Commodity Derivatives Market is thought to be an effective way to manage price risk and market exposure in the South African agricultural markets for all the players involved.
     Farmers can therefore hedge their grain to protect themselves from a possible drop in spot price at the time of harvest. On the other side of the coin, SAFEX also protects millers and grain traders from the effect of price increases when purchasing their stocks.
Storage silos enable the purchase of stocks in advance and storing them in a chosen silo complex for a fee.
     As all SAFEX quotes are based on a theoretical delivered price to Randfontein, the collection at any other destination in the country attracts an adjustment fee known as the silo differential in order to compensate for the theoretical transport costs for delivery to Randfontein. These figures are reviewed on an annual basis and then published on the SAFEX website.
     It may make the most sense for farmers to therefore find a local processing/milling plant and realise a double round of transport cost savings on milled product.
     The South African Government published an Industrial Policy Action Plan 2010/11 – 2012/13 in February 2010 that suggested that the active promotion of investment in the small scale milling segments would contribute to the process of moderating pricing in a key sub-sector that impacts greatly on food costs. Apart from creating new jobs, it could help alleviate poverty by being “particularly competitive in rural areas where high transport and logistics costs raise the price of basic food products”.
     This basically suggested that silo owners and millers could develop “mill door” relationships that provide for grain stocks to be allocated from silo complexes in close proximity to particular milling plants. An alternative approach to bringing down inflated prices resulting from logistics costs could also include the development of small-medium scale grain farmers or cooperatives around proposed new mill sites. Multiple milling sites, based on long grain sources, could therefore work where containing their own smaller silo complexes.
     It still rings true that understanding the position of South African grain storage on a macro level is crucial to understanding the nature of where the grain milling industry, and indeed the grain storage and handling systems incorporated under it, finds itself today.
     Considering micro levels of grain storage and developments continue to stream into the market, be it from local or international sources.
     Again, the grain storage market can be divided into two main sections – raw material and finished product. Varying storage methods are brought together by a standard in HAACP (Hazard Analysis and Critical Control Point) practices such as mandatory fumigation to prevent insect infestation.
     Bringing world-class leading edge technologies in silo inventory management, bunker silo storage and electronic silo certificates is AFGRI Grain Management. It offers secure storage of agricultural products throughout the country providing a total storage capacity of more than 4.3 million tons.
     Its current infrastructure includes 67 local grain silos where grain is handled and stored separately according to grade and other characteristics, with non-GMO grain being a specific example of this practice.
     AFGRI also recently introduced bunker silos, a new technology to South Africa, of which it now has 14 complexes, to provide temporary storage facilities when required.
     Products and services include competitive silo rates, insect-free grain, calibrated mass meters and electronic grain certificates. It also supplies administrative functions such
as stock confirmations and contract administration, bagging, cleaning and drying of grain, third party silo management, separate storage for niche markets and handling and storage services for maize, wheat, sunflower, soya beans, sorghum, groundnuts and dry beans.
     Considering having your own silos then Pretoria-based Silo Warehouse is a good stop for any farmer, miller or businessman when it comes to grain handling and storage. It combines local and international elements in order to provide grain storage and handling solutions tailored for use in African conditions.
     The company specialises in solving grain storage and handling needs ranging from small feed bin-like storage or large and very large silo storage on a farm, railway or a co-operation.
     Although having distribution agreements with two of the world’s best silo manufacturers in the US and Europe, Silo Warehouse manufactures a range of add-on solutions ranging from bucket elevators, chain conveyors, belt conveyors, augers trough-augers, cleaners, aeration systems, aspiration systems and feed milling plants.
     Johannesburg-based bakery equipment manufacturing company M-Bake Bakery Equipment offers equipment designed for the tough African environment that is simple to maintain and operate. It also caters for small and large plant bakeries with silo handling systems ranging from six – 40 ton capacities.
     “One of the most significant advantages brought about by the advent of silos is a clean environment with minimal flour dust. Mills are also willing to discount packaging costs to bakeries with silos,” states M-Bake Bakery Equipment’s Muhammad Lavangee. “And now, with the arrival of fabric and Chromadek silos, silo solutions are much more affordable than ever before.”
     M-Bake Bakery Equipment, in conjunction with its partner Agriflex from Italy, offers value for money silos that are manufactured from either Trevira or Chromadek, to European (CE certification) standards and meets all HACCP requirements.
     Trevira or fabric silos are fitted indoors and are almost a quarter of the cost of steel silos. Indoor silos are also manufactured from food friendly fabrics and are quite common in European bakeries. An added advantage to the indoor silo is that the flour is much cooler coming out of the silo.
     M-Bake Baking Equipment’s outdoor Chromadek silos are a third of the price of steel silos, but are just as durable. All of its silos can be fitted with load cells – enabling more accurate stock control for production purposes.
     Agriflex also manufactures in-line sifters, and has just launched a new and innovative flour cooling system that is ideal for South African summers where the temperature of flour in the silos rises quite high. The company offers solutions ranging from silos through to dosing and are manufactured to the highest standards.
     Silobags afford farmers the alternative of determining their own handling costs due to the minimised transport requirement. The ‘bag’ is capable of safely storing grain on the farm until the farmer is ready to sell it.


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