What Are Browns, Greens, and Grit in Worm Composting?

Composting is a really easy practice anyone can incorporate into their daily life. Like any new habit, it takes a bit of time and knowledge to truly hone in the skill. When you first start getting into composting (which is probably how you ended up on this article), you may hear the terms browns and greens over and over again.

Millions and millions of micro- (bacteria and fungi) and macro- (composting worms) organisms live inside a compost bin. This work force chomps down and poops out your trash to turn it into treasure right before your eyes (over the period of about three to six months). To make sure your compost and its’ critters are moving and grooving, you’ll need to make sure you master the art of adding in browns and greens.

Browns in Compost

Most browns are just that, brown materials. Think uncoated cardboard, dry or dead leaves, sticks, and paper scraps. Browns are the carbon source for your compost bin and help to absorb extra moisture and provide structure to your compost by facilitating air flow and preventing compaction. We recommend adding 2x the amount of brown materials to the amount of green materials each time you feed your bin, ending in brown materials to make sure bugs don't enter your bin.

Greens in Compost

Greens are the nitrogen source for your compost bin, they are often colorful and wet. They offer your bin the nutrients and moisture it needs to make a jam-packed pile of compost ready to take on any garden bed or house plant. Greens are normally food scraps, lawn scraps, or garden waste and they can even be moldy or expired (the worms won’t mind).

Grit in Compost

There's one last term you need to know before diving into the wild, wild world of worm composting. Grit! Worms have a gizzard (instead of teeth) that breaks up food particles, similar to birds. Grit, like sand and eggshells, allows worms to speed up their digestion by carrying food particles through their bellies and out the other end. We recommend adding about a cup of grit into your compost bin each month.

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About Let’s Go Compost

Let’s Go Compost is a national nonprofit making composting simple, affordable, and accessible for schools, families, and communities. Our programs bring hands-on compost education to classrooms across the United States, helping children and educators turn food waste into learning opportunities that build responsibility and respect for the natural world.

Learn more about our programs at letsgocompost.org and support our work at letsgocompost.org/donate.