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The composting season coincides with the growing season. When conditions are favorable for plant growth, those same conditions work well for biological activity in the compost pile. However, since compost generates heat, the process may continue later into the fall or winter.

Hot composting does best when high-carbon material and high-nitrogen material are mixed in a 1 to 1 ratio.

You'll need a pile with minimum dimensions of 3' x 3' x 3' (90 cm x 90 cm x 90 cm) for efficient heating.

For best heating, make a heap that's 4 or 5 feet in each dimension (120 cm to 150 cm). As decomposition occurs, the pile will shrink.

If you don't have this amount of material at one time, simply stockpile your brown materials until you have enough brown and green materials available for proper mixing.

Hot composting piles reach 110 to 160 degrees Fahrenheit (43 to 72 degrees C), killing most weed seeds and plant diseases.

Please note, though, that studies have shown that compost produced at these temperatures has less ability to suppress diseases in the soil since the high temperatures may kill some of the beneficial bacteria necessary to suppress disease.

Steps to Building a Hot Composting Pile

1. Choose a level, well-drained site, preferably near your garden.
2. There are numerous styles of compost bins available, depending on your needs. These may be as simple as a moveable bin formed by wire mesh or a more substantial structure consisting of several compartments. There are many commercially available bins. While a bin will help contain the pile, it's not necessary. You can build your pile directly on the ground. To help with aeration, you may want to place some woody material on the ground where you'll build your pile.

3. To build your pile, use alternating layers of high-carbon and high-nitrogen material, or mix the two together and then heap them into a pile. If you alternate layers, make each layer 2 to 4 inches thick. Some people find that mixing the two materials together is more effective than layering.

   Use approximately equal amounts of each. If you're low on high-nitrogen material, you can add a small amount of commercial fertilizer containing nitrogen. Apply at a rate of 1/2 cup of fertilizer for each 10-inch layer of material. Adding a few shovels of soil will also help get the pile off to a good start; soil adds organisms that decompose organic material.

4. Water periodically. The pile should be moist but not saturated. If conditions are too wet, anaerobic microorganisms (those that can live without oxygen) will continue the process. These are not as effective or as desirable as the aerobic organisms. Bad odors also are more likely if the pile is saturated.
5. Punch holes in the sides of the pile for aeration. If you live in a rainy area, you may want to put a tarp over the compost pile to keep excess water out.

6. The pile will heat up and then begin to cool. Start turning when the pile's internal temperature peaks at about 130 to 140 degrees F (55 to 60 degrees C). You can track this with a compost thermometer, or reach into the pile to determine if it's uncomfortably hot to the touch.

   Move materials from the center to the outside and vice versa. Turn every day or two and you should get compost in less than 4 weeks. Turning every other week will make compost in 1 to 3 months.

7. During the composting season, check your bin regularly to assure optimum moisture and aeration are present in the material being composted.

Finished compost will smell sweet and be cool and crumbly to the touch.

Parts of this article are courtesy of the USDA Natural Resource Conservation Service.

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