How to Activate Your Compost Pile in Cool Weather

The target temperature for optimal microbial bloom in your compost pile is about 45 - 65 degrees Celsius, or about 115 to 150 degrees Fahrenheit. You can buy a soil thermometer at your garden store if you like to be precise about these matters. Or you can simply feel a handful of compost from the center of the pile when you turn it. If it feels warm to touch, your pile is working fine. The correct temperature is easy to maintain during the hot summer months, which also happens to be the time you probably have the most fresh yard and garden refuse to add to the pile. Adding fresh refuse will help the pile quickly reduce to finished compost.

The mid to upper end of the temperature range, about 135F to 150F, is plenty hot to kill harmful insects and larvae that may be in the fresh debris. Remember that if you don't provide enough moisture and oxygen to the compost pile, the temperature can go above 160F and begin to kill off the beneficial microbes. Turning your pile regularly moderates the temperature in the center of the pile.

But when the weather is cool, your compost pile may not work as automatically as it does during the summer. Weather fluctuations in early spring and fall can make it difficult to get the compost pile working. Nitrogen-rich green grass clippings from that first mow will get your compost pile heated up if it seems sluggish in the spring. When you add fresh green material, mix it into the pile thoroughly, fluffing up the lower layers that might be just lounging on the bottom of the pile. You also might want to add a compost activator product.

Compost activators are usually sold as a powder for you to dissolve in water and sprinkle into your compost pile. The powder contains concentrated beneficial bacteria and fungi that occur naturally in the decomposition process. In areas where spring weather is changeable, you can get your overwintered compost pile working early by giving it the microbes it needs. Several brands of compost activators are on the market. Natural Environmental Systems offers an activator powder called Compost Booster. Use a booster in the spring and fall to extend the activity of your outdoor compost pile. If you have an indoor pail-type composting system, mix a dusting of the powder into the pail. Besides speeding up the decomposition process, Compost Booster reduces odors. I also use Compost Booster in the summer when I am deep into harvesting and canning. I can easily amass a three-foot cube of garden and kitchen waste every few days, and adding the booster reduces it quickly. Quick reduction keeps pests and vermin away, and it gives me a fresh, manageable supply of finished compost for my fall garden.

Sources:

Personal Experience
Compost Booster: http://www.naturalenviro.com/productinfo.php?sku=7000-101&surl=compost-starter