F The operation
Cargill has hundreds of trucks coming into the facility each day unloading locally sourced corn from the farmer, which is crucial to keep the non-stop facility running at full capacity. There are five main elements that are used in the refining process of corn, four of these are within the kernel itself: starch (63%), protein (8%), fibre (10%), and germ (4%). Moisture (15%) is needed to soften and separate the kernel into these four parts. In its simplistic format, corn is steeped, ground, separated and washed. It takes 25 incoming trucks to fill one of the ‘tanks’ used in production and to which water and SO2 are added to break down the corn kernels in the initial step. Mr Anderson explained, “Historically, this type of corn wet milling process would extract and separate the corn starch and merchandise the rest.” However, the core business for the value added feed ingredients is within the valuable protein and fibre fractions of corn and these are primarily used for the Empyreal® and Sweet Bran® products that constitute the company’s animal feed division within Starches & Sweeteners North America. Mr Anderson expanded, “The starch and protein are found in the inner portion of the corn kernel and have a distinctive yellowish coloring. The outside is the bran portion and then there is the germ, which is found in the tip or cap of the corn. This gives a lot of starch and very little of the protein and germ in comparison, but the germ and protein are the most highly valued fractions on a per unit basis.” In brief, the grain is steeped and then moved to the grinding section where the germ, fibre, starch and protein are all separated in various ways which includes the use of centrifuges.
The first stage of grinding
The first stage of grinding and the technique utilised is revolutionary. There are two sets of plates that face opposing ways. The corn kernel drops through and is ground and broken to extract the germ. The germ is extracted via a three-stage milling process. The third stage grinds to a fine mixture where the fibre can be completely removed. Corn milling has exactly the same steps, but it is washed after separation, de-watered and then dried. Post-milling there is a seven-stage screening process that further separates fibre from the starch and protein fractions. Cargill utilises large screens that act like sieves. At the first, second, third and fourth stage, there are large gaps in the screen, which get progressively smaller. This allows more of the bran to be caught and less of the protein and starch. Mr Anderson illuminated on the process, “If you look at your first stage that is your dirtiest fibre, the seventh stage is your cleanest fibre and then with the counter current flow, the fibre gets cleaner as it goes one way, which the starch and protein is more concentrated in the opposite direction.” He continues, “It is vital at this stage the separation of fibre from starch and the protein is done correctly, as this affects the amount of protein that can be recovered. But further processing the starch and protein is critical to the outcome of ‘Empyreal 75’.” Adding, “We fail if we send too much protein with the starch and we fail if we leave too much starch in the protein, which will downgrade both products.” Centrifuges play a vital role in achieving densities and removing dry solids from the protein stream and reducing the starch. Starch is further extracted via clamshell cyclones which removes a further five percent of protein from the starch itself 68 | August 2017 - Milling and Grain
getting levels down to 0.3-0.35 percent. Coping with such a high-quality, high-valued product this product has to be handled extremely carefully. It is not bagged on site, but dispatched in bulk by railcar for other facilities across the country for packaging and further distribution. Three or four days of output can be held on site however; demand ensures that product does not need to be stored for long. One single railcar holds approximately 100 tonnes and multiple railcars can be shipped at a time. Mr Anderson says great attention is paid to the railcar container, specifically designed by the company for the purpose of moving product. They are cleaned, inspected and inspected again before use and departure. “There’s a pre-load and a post-load inspection” he explains saying that the cars are automatically loaded and closed hermetically to avoid contamination. Each shipment has samples taken and analysed for protein, moisture, fat and a number of mycotoxins prior to dispatch.
Animal and human food products
Fibre is processed into ‘Sweet Bran’ for cattle feeds with other ingredients added such as milled solubles to lift the nutritional value of the product. When asked about the use of the fibre for Sweet Bran cattle feed, we were informed that once the germ and fibre is separated, just the starch and protein is left. If there is too much protein with the starch, it means the Empyreal formula is wrong, and the same goes for Sweet Bran. The centrifuges previously mentioned can pump 700 gallons per minute of material processed in a very rapid pace and the speed or flow of the material can be adjusted by a simple value. The result is, speeds of around 3000rpm let the lighter material rise to the top and the denser raw materials fall to the bottom. This works in conjunction with clarification, which is another centrifugal force, but with a slightly different configuration. Clarification separates just the water from the mixture and moves the consistency of the protein from five to 14 percent solid. At this stage there is still 25 percent starch content. At the end of the process, we were told that, “there’s only about 0.3 percent ratio of protein left to starch, and that’s where we will be sending it to be turned into the dextrose or high fructose corn syrup.” Also from the starch by-product high fructose corn syrup, fuelgrade ethanol, dextrose and fermented products such as lactic acids and low calorie sweeteners are produced and supplied to other partners on the campus for processing into products such as Lysine. Cargill’s diversification on the site has given rise to new products. Together with its joint venture partner for example, Cargill is also making corn-based biopolymers or plastics on the site. Mr Anderson noted that, “Cargill’s model for its campus is plug-and-play. We supply all the utilities such as water, water treatment, chemical handling, heating and electricity, etc., to those companies joining us.” For example the site uses and treats, and returns 13 million gallons of water per day to the Missouri river, more than twice the amount the local community of Blair uses and the same as the city of Omaha. Expanding he commented, “The focus is on short supply chains, the efficient utilisation of natural resources such as the adoption of heat exchanges in the production process which has reduced the consumption of energy and results in more value to its customers and helps meet the output goals that have to be met by the company.”