Distillers grain – a coproduct made through the distilling process – has been used for animal feed for centuries. Though often summarily dumped into sewers and rivers by brewers and distillers, numerous areas in Europe began to utilize distillers grain in the 1700s as a food source for their livestock.
The invention of the Coffey still in 1830 largely automated the distilling process and increased the availability of distillers grain, which proved considerably less expensive than whole-grain animal feeds. Yet in its wet form, distillers grain could only be used locally, as its shorter shelf life and heavier weight made transporting it cost-prohibitive.
In the United States during the late 1800s, however, advances in technology allowed for drying these coproducts, lengthening how long they could be stored. In 1907, the first study to look at feeding distillers grain to cattle was published, and the early 1900s saw new research into its use specifically for dairy cattle. By 1915, the Society of Animal Science Committee adopted definitions explaining what distillers grain consisted of. Though alcohol prohibition in the United States saw production screech almost to a halt during the 1920s, distillers grain for feed resumed in the 1930s. The energy crisis of the early 1970s saw a new use for distilled ethanol, with ethanol distilleries now also providing a source for distillers grain.
Sources & Content of Distillers Grain
Traditionally, distillers grain comes from brewers of beer and distillers of spirits. Large distilleries and breweries generate vast amounts of excess grain, which they typically sell to animal feed producers. Smaller breweries often did the same on a smaller scale with their spent grain from the brewing process, partnering with local animal farmers who used it to feed their livestock.
Made up of a crumbly porridge of barley, oats, rye, and wheat, this offal from distilleries and breweries looks like a waste, though it’s packed full of proteins, fats, and fibers. With well over eight thousand in operation, the growing number of American craft and regional breweries has made them another growing source for distillers grain. Typically, these smaller breweries produce about two tons of spent grain weekly, though many of them can’t easily access markets for their used grains.
Increased ethanol production for biofuels, especially since the 1990s, has made this a growing source. Manufactured in these industrial distilleries through the drying of mash, it’s become standard fodder for livestock. The ethanol industry mainly provides a corn-based distillers grain that’s high in protein, which also decreases risk of subacute acidosis and increases efficiency for beef cattle.
Nutrients for Animal Feed
A ready source of energy and protein for livestock, beef cattle especially benefit from including distillers grain in their diet. It can be used as a supplement for calves, heifers, and cattle being raised for market. Starch content is lower while fiber and protein content occur at higher levels than that of corn. In fact, many samples of distillers grain contain between 25-35 percent protein. However, some distillers grain has higher phosphorus, sulfur, or rumen-undegradable protein content. For this reason, it’s important to measure nutrients within distillers grain to ensure animals’ diets are appropriately balanced.
Potential Use as Human Food
While an excellent source of animal feed, distillers grain also contains nutrients that make it nutritionally fit for humans. What was once considered the dregs from the distillation process can be turned into flour for baked goods. With a sufficiently developed supply chain, large commercial bakeries and other food processing companies can make use of it, drying the spent grain from microbreweries and grinding it into flour. This would reduce billions of pounds of waste that occurs annually within the industrial food processing industry.
Producing Distillers Grain
Grains that are leftover from the beer brewing or spirit distilling process contain malt barley, corn and other grains. Hops and other ingredients are also used to preserve and flavor brewed products. These grains go through a mashing process, after which hot water is added and turns the starch into sugar, which along with yeast turns it into drinkable alcohol. For distilled spirits, the yeast is largely removed. Whether undergoing a brewing or distilling process, the spent grains are a marketable product, with many larger brewers and distillers sending this byproduct on to livestock farmers for feed.
The primary method for producing ethanol for fuel in the United States is the dry grind process, which uses the entire corn kernel during fermentation. It involves screening and milling corn with a hammermill into meal, which is then ground into a flour that’s then combined with water to form a slurry. Enzymes are then added to break down starch into glucose, with the resulting mash heated to kill undesirable bacteria and turn the starch into gelatin. Enzymes continue breaking down the starch after it’s cooled, with yeast added next. This converts the glucose to ethanol and carbon dioxide as the yeast metabolizes during the fermentation process. Once fermented, the distillation process extracts the ethanol, with the remaining solids and water collected.
Wet vs. Dry Distillers Grain
Regardless of whether the alcohol being made is for human consumption or fuel, these remaining solids are what becomes distillers grain. The spent grain is separated from this mixture then centrifuged, or otherwise separated, to divide the liquids from coarser solids. These coarse solids – referred to as distillers wet grains – are then collected from the centrifuge or separator, where they can be further processed into distillers dry grains with solubles.
Containing unfermented grain residue and having between 65-70 percent moisture content, wet distillers grain has an extremely short shelf life. Due to this high moisture content, it can only last from a week to a month, depending on the conditions in which it is stored. This is what smaller breweries or distilleries would traditionally provide to local animal farmers. Many ethanol plants also provide wet distillers grain as feed to local feedlots, which cuts down on associated drying costs.
Distillers dried grain with solubles is essentially the same product with most of the moisture removed. As its moisture content is only about 10 percent, dried distillers grain can last almost indefinitely, making it easier to ship as well as a more valuable coproduct. These dried solids are used to make animal feed. However, the drying process can also significantly add to the cost, making up about 30 percent of the cost of dry milling plants.
Prater Solutions: Equipment for Removing Moisture from Distillers Grain
Along with mills and other equipment used to break down grains to produce alcohol, Prater Industries makes equipment suitable for removing moisture from and drying wet distillers grain. Further processing results in a more valuable coproduct: distillers dried grain with solubles.
Key pieces of Prater equipment useful for processing distillers grain are:
- Prater’s Rotordryer by IPEC dries wet distillers grain, feeding the material into the main section where it’s ground and dried. A grinding rotor separates wet material until it becomes very fine and acts like as fluid within the grinding chamber. When exposed to high temperatures from the hot air blowing in from an air heater, it causes most of the water within the grain evaporates rapidly.
- Prater’s Hammer Mills are the ideal size reduction equipment choice for grain processing in brewery and distillery applications. The hammer mill’s pulverizing action and controlled screened discharge provide a consistent end-product at the desired finished particle size. This maximizes the enzymatic activity, converting a significantly higher percentage of starch to sugars and translating directly into less grain necessary to achieve the desired quality.