Green Versus Brown Compost Materials

Posted by Chris Field
May 23rd, 2008
Filed in Compost
Tags: Compost, fertilizer, garden, manure, organisms, Soil and Fertilizer

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Composting in your garden is very easy to do, however, to achieve quick and optimal compost, it should be well balanced with green and brown waste materials.

What are green versus brown materials, and why should you care? Think of compost as a healthy meal for your soil life – those worms and microbes that do the actual work of turning your waste into dark, rich compost. Just like anybody or anything else, a proper diet is essential for growth and health. Humans can’t live on only french fries (though that would be great!) — in the same vein, composting microbes can’t only live on grass clippings. They need both green and brown ingredients.

Brown Materials

Brown is the carbon energy the compost microbes need to thrive. Without it, your pile of green kitchen scraps will become smelly and slimy. This is because your greens will decompose too quickly through the bacteria already in the materials, rapidly fermenting nitrogen into the rotten egg smell of ammonia.

You want enough brown materials for the good bacteria and microbes to have enough energy to multiply and slow down the release of nitrogen. The layering effect of compost is a natural way to do this.

If your compost has a rotten rather than rich, earthy smell, add some more brown materials to the mix. Stir it as well, as a lack of oxygen also contributes to unpleasant smells.

Brown materials are stocky and coarse, and include:

• dry yellow or brown leaves and grass
• the woody stalks of plants such as sunflowers and corn
• paper and wood products, such as sawdust, chopped up twigs and shredded newspaper
• dryer lint
• straw
• wood ash (not too much)

Green Materials

Nitrogen is the protein the munching microbes need to thrive. Too little nitrogen, and your pile will decay into compost a lot more slowly, though it eventually will. The microbes will be fewer and weaker, so it could take a year or two in a mainly brown compost pile to turn into rich compost. A well-balanced compost will be hot, due to all those microscopic bodies busily multiplying and feasting for you!

Green materials are soft and often wet, and include:

• Kitchen scraps, such as vegetables, melon rinds, eggshells and fruit
• coffee grinds with the filter and tea bags
• fresh green leaves and grass clippings
• fresh weeds that haven’t seeded (seeds will likely survive the composting process)
• composted manure – cow, sheep, chicken, rabbit
• hair – scatter the hair in the bin, not in clumps

The Proper Ratio of Brown and Green Compost

A number thrown around is 25 to 30 parts brown to 1 part green. This doesn’t mean throwing in a massive amount of browns and only a tiny but of green – instead, it refers to carbon versus nitrogen, not the organic matter you throw in the compost. Everything is made up of carbon, greens and browns. Green just happens to have more nitrogen in it because — well, the green color partly gives it away. Seriously, though, all living things are a mixture of carbon and nitrogen, and after death, the nitrogen is released, turning green grass and leaves brown. Coffee grounds and manure are good examples of nitrogen-rich but non-green products.

Equal amounts brown and green will achieve the proper ratio of 30:1. Well, close enough. Let’s not make things overly complicated – a good rule of thumb is to add a bit more brown material than green.

Add some water, turn your compost every couple days, and viola, after a few weeks or months you will have a great source of soil conditioner and organic fertilizer for your garden and vegetable plants! The richer and more varied the compost diet, the healthier the environment for your microbes to thrive in.