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How to Compost Spent Grains

By Tracy Morris ; Updated September 21, 2017

Approximately 92 percent of brewing ingredients used in the manufacture of beer are wasted, according to the Zero Waste Research Institute. Most of this waste comes in the form of spent grains. And while the majority of home brewers discard these spent grains, they are still packed with nitrogen. One good solution for spent grains is to compost them. Because of their high nitrogen content, spent grains are considered an organic green product. When mixed with carbon-rich organic browns, they decompose into black loamy soil in a short period of time.

Layer organic nitrogen filled green material such as spent grains, grass clippings, kitchen scraps and clover and carbon rich brown materials that include wood shavings and dead leaves in alternating layers in your compost bin. Your brown layers should be twice as thick as your green layers.

Build your pile so that it is at least 3 feet square, but no more than 5 feet square.

Wet the pile to activate the decomposition process. The pile should be just as wet as a wrung out sponge.

Check the internal temperature of your compost by inserting the probe from a compost thermometer into the compost pile. The probe should extend into the center of the pile for an accurate reading. The pile's core temperature should be between 130 and 150 degrees Fahrenheit.

Stir your compost with a pitchfork whenever the temperature falls below 130 degrees. As you mix the compost you will notice that all the material that was at the center is now broken down into the texture of dirt. Shift new material to the center of the compost pile so that it will be broken down in the same way. Shift the dirt-textured compost so that it is located along the outer regions of the pile.


Things You Will Need

  • Compost bin
  • Organic brown material
  • Organic green matter
  • Garden hose
  • Pitchfork
  • Composting thermometer


  • To facilitate speedier breakdown of organic material, chop your compost material into bits that are less than 1 inch square. Kitchen scraps may be reduced with kitchen shears, and yard wastes may be cut down by running over them with a lawn mower or feeding them through a wood chipper.

About the Author


Tracy Morris has been a freelance writer since 2000. She has published novels and numerous online articles. Her work has appeared in national magazines and newspapers including "Ferrets," "CatFancy," "Lexington Herald Leader" and "The Tulsa World." She holds a Bachelor of Arts in journalism from the University of Arkansas.