A Thermal Compost Pile—The Right Ingredients and a Little Elbow Grease
If you’re lucky enough to live in America’s “breadbasket,” places like Iowa, Illinois, Indiana, Wisconsin, Michigan and Ohio, it seems like you can throw just about any seed into the soil and count on a bumper crop of tasty homegrown vegetables. The last ice age left glacial soil, offering the ideal mix of sand, silt and clay, along with great drainage and nutrient retention. Of course, you can go to the local hardware store or nursery and get the ingredients for a health raised bed, including peat moss, garden soil, mulch, compost, manure and perlite. But you can also do what Mother Nature does—create rich compost in your back yard, with just a handful of ingredients, some hard work and a little time.
What Is Thermal Composting and How Is it Different from Other Types of Composting?
Virtually anyone can create an ample amount of compost in the corner of your yard, in a space that’s just 3 feet by six feet. The process is known and “thermal composting,” and it’s probable different from what most people think of when they hear the term composting. Thermal composting doesn’t use most kitchen scraps, so it’s typically not a place for egg shells, banana peels and coffee grounds.
Thermal composting gets its name from the fact that it generates a bit of heat, actively converting a few substances to useable compost. Here’s how it works:
- You start with layers of different organic materials
- Those materials are saturated with water, which facilitates the chemical reaction, which in turn generates heat
- You periodically “turn” the pile, which introduces oxygen into the process, feeding the aerobic bacteria that help break everything down
- The pile will continue to generate heat as decomposable materials are converted to compost. When all decomposable materials have been used, the pile will naturally cool down and is ready for use in a garden.
How to Create Your Own Thermal Compost Pile
To generate your own thermal compost, follow this process:
- Mark off an area that’s three feet square, ideally with metal poles. Add another two poles exactly three feet from one end of the square. If possible, have the poles protruding three feet above the ground, so that they form side-by-side cubes that are 3 feet on all sides.
- Gather your materials—you’ll need:
- Green materials—These are almost any plant that was alive shortly before it went in the pile—grass clippings, garden plants at the end of the growing season, leaves or branches that came off a tree in a storm
- Brown materials—These are materials that died a natural death…think leaves that you rake up in the fall. Wood chips, paper, cardboard, sawdust and long-dead twigs and branches are good brown materials
- Nitrogen-based materials—The most commonly used form of nitrogen is well-aged manure, but legumes, such as green bean and pea plants are also good sources of nitrogen
- Layer the materials in one 3×3 area—The ratio is 2 parts green to 2 parts brown to 1 part nitrogen. It’s easiest spread 2 inches of green, two inches of brown and one inch of nitrogen until the pile is three feet tall.
- Completely soak the pile with water, so that it has the consistency of a wet sponge
- After three days, get a pitchfork out and turn the pile into the adjacent 3×3 area, doing your best to mix up the materials as you do. Soak with water when you are done. Repeat every 3-7 days.
- You should feel some heat when you get close to the pile…it can get up to 160 degrees Fahrenheit. After about 8 weeks, you can stop turning the pile and wait for it to cool.
