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I'm attempting to learn how to compost. Most of the material available to me is grass clippings (not many leaves on my property). I had success last year, but this year my pile is exuding a strong odor. The composition of my piles are roughly as follows:

2017

  1. Grass clippings: 82%
  2. Coffee grounds: 9%
  3. Chicken manure: 6%
  4. Fruit / vegetable scraps: 3%

2016

  1. Grass clippings: 73%
  2. Wood chips: 7%
  3. Composted steer manure: 6%
  4. Sand: 6%
  5. Coffee grounds: 5%
  6. Fruit / vegetable scraps: 3%

The 2016 pile didn't really smell much. The 2017 pile has a barnyard odor (somewhere between a cow manure and chicken manure smell)--sometimes detectable 60 ft away when the wind is blowing.

The volume of both piles is roughly the same (1 - 2 yards). I've kept both piles watered (roughly the consistency of a wrung-out sponge.) I've turned each pile every 1 - 2 weeks.

Any ideas why this year's compost pile smells more than last? Is it just the fact that I used rawer chicken manure (it didn't smell that bad when I took it out of the bag) than the already composted steer manure I used last year? Is it the absence of wood chips? Is it the high acidity of the coffee grounds along with the nitrogen from the grass? I applied fertilizer to the grass this year before I mowed it and put it on the pile. Putting lime on the 2017 pile seems to have helped some.

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Your CN ratio is off, that's why it smells bad. CN ratio is often referred to as browns to greens, the C standing for carbon and the N for nitrogen. Your grass clippings are high in nitrogen, but the CN ratio should be 4:1, meaning 4 parts carbon or browns to 1 part nitrogen or greens. Your compost has the reverse ratio, and the difference between last year and this is the wood chips, which count as carbon.

If you have nothing else that counts as carbon, you could add some shredded paper, so long as it's not got colour print on it, that would increase the carbon ratio; mix it in well and that should reduce the odour over time. More info can be found here: Understanding The Browns And Greens Mix For Compost.

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    Another inexpensive option if you don't have enough paper handy might be to pick up a straw bale. They generally run under $5, and one bale will generally last an entire season. If my pile starts to smell, I just add a few inches of straw on top, and it takes care of the problem. – michelle May 31 '17 at 16:56

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