The grain left in the still after the ethanol is boiled off is a useful animal feed, because making ethanol uses up the starch but not the protein, so the residue is roughly a third of the grain’s dry weight with about three times its protein share. Feed it wet and fresh to cattle, pigs or poultry within 24 hours, or dry it for storage, and bring ruminants onto it gradually.
Part of Ethanol Fuel Production
Distillers’ grain is the solid residue of fermented and distilled grain mash, used as protein-rich livestock feed.
The Fermentation Takes The Starch And Leaves The Rest
Starch makes up most of a grain’s dry weight and is the only part yeast turns into ethanol and carbon dioxide. Protein, fibre, oil and minerals pass through. The parent calls the residue rich in protein, from yeast cells and unfermented grain protein, and says to feed it wet to cattle, pigs or poultry within 24 hours, or dry it for storage.
Worked Example: One Tonne Of Corn
Inputs (grain at 15% moisture, dry matter 850 kg; the starch figure comes from the parent’s 370-400 L per tonne, worked back in Starch Crops; the 9% protein share is a recalled typical value for corn, not a corpus figure):
- Starch consumed: 541-585 kg of the 850 kg dry matter.
- Dry matter left: 850 − 585 = 265 kg up to 850 − 541 = 309 kg.
- Protein in the grain: about 9% of 1,000 kg = 90 kg, nearly all of which remains.
- Protein share of the residue: 90 ÷ 309 = 29% up to 90 ÷ 265 = 34% of its dry matter, against about 9% in the grain, roughly three times.
So one tonne of corn gives 370-400 litres of ethanol and about 265-309 kg of dry feed. The feed does not return the starch’s calories; it returns the protein and fibre. In terms of the food-fuel trade, the grain’s 3.64 million kcal as human food (3,638 kcal/kg) is not recovered by feeding the residue to livestock, though the animals’ meat, milk or eggs give some back (Dairy and Egg Calorie Efficiency).
What You Need
- Spent grain from the still pot or from straining the wash, collected after it cools
- Animals to eat it: it suits cattle, pigs and poultry per the parent; ruminants cope with fibre best
- Storage: a cool shed with a lid for a day’s worth; or a drying floor, and a dry sack store for dried grain
Method
Step 1: Cool and drain. Let the stillage cool; separating thick solids from thin liquid is easier cold.
Step 2: Feed fresh. Mix into the daily ration within 24 hours, since wet residue sours quickly (parent).
Step 3: Introduce slowly. For cattle, switch feeds over 10-14 days and keep at least half the ration as long-stem fibre (Feeding and Nutrition). Watch dung and appetite.
Step 4: Dry what you cannot use. Spread thin in the sun or on a warm floor, stirring until it is crumbly and does not smell sour, then store dry and covered (Grain Storage).
Common Mistakes
- Feeding sour residue. Spoiled wet grain makes animals ill; discard at the first sour smell.
- Making it the whole diet. It is a protein supplement, not a complete ration.
- Feeding residue from a pot cleaned with lye or other chemicals that was not rinsed out; keep the feed stream clean.
- Forgetting that heat leaves with it. Hot residue scalds; cool before handling.
Cool before you shovel
Spent wash leaves the still at about 100°C and holds heat for hours. Keep children away, let it cool before handling, and never discard it into drains or ponds where it will rot and remove oxygen from the water.
What’s Next
- Learn next: Methanol Hazards, the other byproduct concern
- Combine with: Pig Husbandry and Cattle Management, for who eats it