Image credit: nancybeetoo, used under Creative Commons license.
From taking my compost with me when I moved house, to composting the waste produced by the move, I am well known for being a little obsessive when it comes to all things compost-related. It is, after all, a truly miraculous process that represents the very heart of what it means to live sustainably. If you're a newbie to composting, one of the most striking experiences you are likely to have is the first time you ever experience a truly hot compost heap in action—reaching temperatures of as much as 80 degrees centigrade. Want to try it for yourself? I've just come across one first-hand account for a simple, continuous hot heap composting system that produces usable, friable compost in as little as 3 weeks!When I took my first permaculture course, a large part of the curriculum was centered around composting and the recycling of organic matter. Besides low-labor, slow composting systems that work at low temperatures, we also explored the process of making hot compost. I knew, of course, that compost can heat up as a result of the bacteria working inside it—but I had no idea just how hot even a relatively small heap could get. Having built a mixed pile of animal bedding, raw manure, crop wastes, and cardboard scraps, we left the heap for a few days to warm up. When we came back, our teacher asked each of us to roll up our sleeves and stick our arm into a hole in the heap—the experience was astounding. Having gotten over the typical urbanite's squeamishness of putting our hand in a pile of poop, we were amazed at how difficult it was to keep your arm in for more than a few seconds.
This exercise was not just a way to demonstrate the awesome biological processes going on in compost. As our teacher explained, it is also a very practical method to make sure the compost is progressing as it should—if you can hold your arm in for longer than a few seconds, the heap is not hot enough and should probably be turned, and have more nitrogen rich material added, or at very least built better next time. If, however, you can't even hold your arm in at all, then the heap is too hot. (An overly hot heap loses excessive amounts of nutrients, and may even catch fire!)
For those wanting to try all this for themselves, the Permaculture Research Institute of Australia has a great account by Alex McCausland of Strawberry Fields Eco-Lodge of their super-fast 3-week hot composting system. Using a series of small pits dug into the ground, McCausland and his colleagues pile up a carefully layered mixture of crop waste and dry grasses, kitchen scraps, and animal manure (at a ratio of 3:2:1). The mix is constantly watered as the pile is built, and the layers are repeated 3 times. After this, a small amount of compost from an existing heap is added to ensure a "starter" of the appropriate bacteria, and holes are punched through from top to bottom to allow heat to rise and oxygen to circulate. The mixture is then allowed to heat up for 3-5 days before being turned to ensure even decomposition, and the destruction of weed seeds throughout the pile.
Within 3 weeks, says McCausland, he has a beautiful, fertile and fluffy humus ready for use in the lodge's vegetable gardens. Next up, the team plan to make a compost-powered water heater to provide hot showers for themselves and their guests. (See the trailer to Geoff Lawton's Permaculture Soils for an idea of what this might look like.)
More on Composting and Soil Care
Dirty Movie Reveals the Secrets of Abundant Soil (Video)
Is Male Pee Better Than Female Pee? The Compost Conundrum
Build Your Own Compost Tumbler
Moving Your Compost When You Move House