When I first started teaching composting, a friend brought her new baby over to meet me. I said, “Come in the back yard and see my 1o compost piles!” She wouldn’t go into the yard because she was afraid the smell would make her son cry. I assured her I wouldn’t have 1o compost bins in the yard if they smelled badly.
When I finally coaxed her outdoors, she was shocked. “Mary, your compost doesn’t stink at all. How can that be?”
The answer is that I build piles correctly and I know what to do if one starts going awry. You can too. Build your pile correctly, then use the following corrective measures if you detect foul odors from your pile.
Improper Proportions of Carbons to Nitrogens
Solution: Restack the pile, adding more carbons as you go.
Nitrogens generally rot faster and, therefore, stink more. Carbons tend to rot more slowly and stink less. So if your pile stinks, a major consideration should be your Carbon to Nitrogen ratio. You can get a calculator and do the math if you want to, but most people just use about half carbons and half nitrogens by volume (not by weight). If your pile is stinking, you probably used too much nitrogen. So just restack your pile, adding more carbons to increase the carbon-to-nitrogen, or C:N ratio.
Top Layer of Pile is not Carbon Material
Solution: Add a layer of carbon material to the top of the pile. Always build your pile with a layer of carbons on top.
Just as important as the proportion of carbon, is the placement of the carbon materials. The final 6” layer on top should be entirely of carbon. If your top layer is fresh manure or rotting food scraps, your pile will stink. There is nothing to absorb the odor. The top 6” of material should be carbons.
Pile Built on Ground with Poor Drainage
Solution: See Compost Pile is Too Wet.
Even if your pile is on ground with poor drainage, there my be pockets within your pile that have gotten waterlogged and gone anaerobic. If so, these need to be pulled apart and mixed with dry carbon materials. Try to mix in different types and shapes of materials to reduce matting.
Improper Inputs for a Home Pile
Solution: You may have to dispose the problem materials another way. But first, try mixing them with other materials. If you’ve made an entire pile out of one material, divide it up into three piles and mix with materials that are different shapes and sizes, as much variety as you can find.
Did you put something in your pile that should not be there? Roadkill or other meat, for instance? Oil? Dairy? These things do not compost well in a home pile and they tend to give off very unpleasant odors. That’s why I suggest you not compost them in a home compost pile. (Large composting operations can usually handle them if they choose to.)
If that’s not the problem, consider that you may have too much of an item that would be okay in a home pile in smaller quantities. A man once posted a message to my forum saying, “I just cut my dog’s hair. Can I put the clippings in my pile?” I told him yes, but to sprinkle them around the entire pile so they wouldn’t mat together.
He came back a few days later SO ANGRY with me. “You told me I could compost hair!”
“You can,” I told him. “What’s the problem?”
Because I told him he could put one dog’s trimmings in the pile, he decided that the logical thing to do was extrapolate my advice into a large quantity scenario. He went down to the local beauty salon and got 10 large yard waste size plastic bags full of hair cuttings. He had created a 4 x 4 x 4 foot compost pile out of hair, watering every 4 – 6”. This was not the few wisps of natural dog hair he had asked about. This was salon hair – chemically treated, colored, bleached, dyed, hair-sprayed and gelled.
It was a mess and it stank. No surprise there. The surprise was that he had decided it was my fault. But I digress. . .
My point is that you can create a problem when you rely on only one type of material. The pile needs dissimilar shapes and sizes and types of materials to provide space for water and air-flow and to give decomposers variety in their diet.
Mary Tynes, Master Composter, www.mastercomposter.com
Image Credit (top left): http://www.flickr.com/photos/fishermansdaughter/4238994386/
Image (bottom right): BioPod Plus