Spent Grain

The Brewing Process

Brewing Diagram.png

This is a simplified look at the traditional brewing process.  Malt, consisting primarily of barley and other grains, is added to the mash tun and filled with water.  This is then heated to a point where the sugars from the grains are separated and dissolved into the water.  This water is then moved to another tank where it is fermented with hops and yeast.  After fermenting, it is filtered and conditioned into drinkable beer.  

After the grains are utilized for their sugars in the mash tun, they are disposed of as what is referred to as spent grain.  These grains are high in protein, fiber, and fat, but lack sugar because the brewing process removes them. However, the nutritional value is hard to capture due to the high water content and quick spoilage.  Below is some more information showing the difficulties of this valuable by-product.


Spent Grain Statistics


80 - Percent Moisture Content

85 - Percent of Brewery Waste

24 - Hour Usable Life (Wet)


Spent Grain Problems

Spent grain spoils very quickly.  When a brewery smells sour, or funky, this means there is spoiling spent grain that has yet to be disposed of on the premises.  If it is kept on site for more than a day or two, this smell becomes very potent.

Spent grain contains over 80 percent water.  This means that when these grains are transported, over 80 percent of the costs and emissions from this are due to the water content, only 20 percent for the actual grains.

Current disposal methods all involve either transporting water-heavy, time-sensitive grains significant distances, or creating expensive, small-scale alternatives.  These options consist of:

  • Giving it to a farmer for animal feed, relying on prompt collection and transport. This can prove especially difficult for urban breweries.

  • Anaerobic Digestion. This can create bio-fuel, but is very capital intensive and cannot process a large and consistent output of spent grain.

  • Landfill. This is the worst possible option due to the transportation costs associated and the methane and CO2 released into the atmosphere during decomposition.


Check out how GrainHaus is changing the way breweries handle their spent grain here.