“Another innovation I expect to see in the near future is grain bins manufactured with composite materials. Plastics and steel would make a lighter structure reducing the cost of the concrete foundations, which makes a huge portion of the capital cost in a new facility. They would also provide better thermal insulation. A wire mesh would discharge static and provide structural strength, while the plastic acts as a physical barrier and an insulator against the weather.”

Prof. Gustavo Sosa Industrial Mechanical Engineer Licensed Grain Inspector MBA Project Management SOSA – Engineering Consultants ing.gustavo.sosa@gmail.com We are experiencing an increased demand in systems for the organic treatment of grains. The consumer is willing to pay extra for products that haven’t been exposed to chemicals. Besides, the use of pesticides increases the risk for workers in our industry and they harm the ecosystem in the area. Dead insects are eaten by birds and rats, which die poisoned, and in turn poison their predators. Of course, killing rats and birds is desirable, as they eat the grain and the flour too, but the damage to the environment should be contained as much as possible. As professionals, we know the effect of most pesticides disappears after a few weeks, but we can’t expect the consumer to acquire this specialized knowledge, not even to believe us.

Some decades ago, the refrigeration for grains appeared in the market. It promised to be the best system ever for grain storage, but it was stopped by the high cost of the system itself and the high cost of electricity. It was only in a few places, like Spain, that it became widely adopted, but even in places with warmer temperatures (like Brazil), it is hardly known.

Recently, we are seeing many researchers studying (or just cleaning old studies) on the use of nitrogen (N2) and carbon dioxide (CO2) to create a “controlled atmosphere” (also known as “modified atmosphere system”) inside the grain bins. The trick is the same: filling the grain bins with a cheap gas that would deprive the insects and fungi of any oxygen. Both nitrogen and carbon dioxide are natural occurring gases that don’t harm the environment. They are also non explosive. The issue with carbon dioxide is that it may cause corrosion in steel by increasing its alkalinity. And some people may complain about greenhouse effects, but the quantity is too small to care. The other caveat is that MAS doesn’t prevent spoilage after the atmosphere comes back to normal, so you have to keep it sealed all the time you have grain inside the bin.

As with refrigeration, this technology has been around for 40 years, but never took off. The reason is that it requires hermetic grain bins (smoothwall bins), and only a couple of bin manufacturers (worldwide) offer this kind. The easy way to have a hermetic grain bin is just using an old-fashioned tank, but they are very expensive. A liquid doesn’t lead to the dynamic stresses exerted by bulk solids in the walls and floor of a bin. This means a smooth wall grain bin would need thicker walls, meaning more steel, meaning more money. You can also cover the grain bin with a tarp, but on large bins it is not possible and it is cumbersome in every case.

You also have to pay for the gas, which has to be supplied by a company like Linde or Air Liquide. However, you won’t have to pay for electricity, as the grain in a MAS doesn’t require aeration.

Now bear with me as I try to make a comparison between the cost of using MAS and the cost of using standard aeration.

Cost of nitrogen: EUR 0,70 per cubic meter. Grain bin size: 1.592 m3 Bin diameter: 12,23 m Wall height: 14,92 m Cost of electricity: EUR 30,5 per 100 kWh Standard aeration flow: 9,0 m3/m3/h Fan air flow: 9 * 1592 / 3600 = 3,98 m3/s Air speed: Flow * Bin volume / Bin area = 4,0 / 117,4 = 0,03 m/s Let’s round that up to 0,10 m/s just to be able to use the standard tables.

So that gives 30 mm water per each meter height of stored wheat. Let’s call this “grain load”. Fan pressure: Bin wall height * Grain load = 15 * 30 mm water (approx.) = 450 mm water = 44,1 bar

The aeration system we need has to handle around 4 m3/s and 44 bar. Considering a global efficiency of around 50%, the fan power must be about 20 kW. Considering 3 hours on everyday, it makes 1.800 kWh every month. That makes about 540 EUR every month of aeration.

On the other hand, if the space occupied by gas inside the grain bin is 50% of it, then you need about 800 m3 of gas. 0,7 * 800 = 560 EUR. But the gas will keep your grain fresh as long as the bin is sealed. Then, every month after the first month is more money for you.

All these are just napkin calculations, to show there is a need and a market for hermetic grain bins. I expect you to challenge them and adapt them to your bin sizes and local prices.

These calculations may be performed much more precisely, but my idea here is just showing that the order of magnitude is similar and purchasing hermetic silos might be attractive for long term storage.

The results are more dramatic if you think that, in a MAS, grain may be stored wet in a warm weather. That’s why I believe the commercial availability of hermetic grain bins will lead to a paradigm shift in grain (and flour) storage. There is a lot to be discovered.

Another innovation I expect to see in the near future is grain bins manufactured with composite materials. Plastics and steel would make a lighter structure reducing the cost of the concrete foundations, which makes a huge portion of the capital cost in a new facility. They would also provide better thermal insulation. A wire mesh would discharge static and provide structural strength, while the plastic acts as a physical barrier and an insulator against the weather. Current FEA (finite element analysis) modelling can optimize the design to avoid the complicated loads and ad-hoc solutions improvised for projects in the past.

Using (again, old news) a honeycomb arrangement of bins built with this technology we could maximize the use of land and better segregate the grains according to qualities and properties. Dwight Kinzer has a patent on a conveying system specifically for this kind of facility.

The Kinzer system (Hex-Pak) allows for a very detailed segregation of grains according to varieties, moisture, and other characteristics, at a fraction of the cost of what a traditional system would require. It also provides a fool proof system to perform traceability, which is impossible in the traditional larger bins. In the traditional system, grain is just a commodity and you switch grains inside the bins as farmers bring it in and millers take it out. In a Hex-Pak, you can separate the shipment from each farmer and tell the miller exactly what he is buying. Imagine being able to do that after a fusarium alert? As I said in a previous article, the world is moving in the direction of complete customization. That’s what 3D printing (my guilty hobby) is for. You can download a design from internet (www.thingiverse.com) and print it at home. Or you can design your own, using cheap and easy software like TinkerCAD. Currently you can buy a custom-tailored suit over the internet. Why not ordering a customized flour? The percentage of people in the world, living in poverty in 1981, was 44%. Right now, it is below 10%, and still declining. As more and more people are lifted out of poverty, they will want products of higher quality. As you have more money, your uniqueness becomes more important. Maybe you have gut problems and need more fiber. Or your kids only eat pasta, so you want more vitamins and proteins in the dishes you make for them. That’s what customized flour could do. The technology that we need is already available. The hardware is there. We just need the imagination to make it a reality and accelerate our way into the future.