Building A Hot Compost Pile

Key Points to Remember

• Use equal amounts of "greens" and "browns."
  
• Mix together a variety of ingredients.
  
• Shred or chop all ingredients, if possible.
  
• Build the pile large enough to retain heat.
  
• Turn or aerate the heap regularly to let in the air.
  
• Keep the pile as moist as a damp sponge.
  

Directions

1. Gather both "green" and "brown" ingredients, enough to make a compost pile measuring at least 1 meter (3 feet) in each direction (high, wide and long).
   
   A smaller pile won't generate or retain enough heat to effectively kill any harmful bacteria present. If you choose healthy ingredients to compost, and keep pets and pests out, there's no reason for concern.
   
   A much larger pile is more likely to compact, shutting out air, and is more difficult to work with.
   
   
2. Chop or shred into small pieces as much of the material as possible. Dry materials like leaves can be run through a shredder or under a lawn mower. A whipper-snipper in a garbage can works well too, like a big blender.
   
   Shredded materials make a better home for decomposer organisms, with more surface area for them to work on. A shredded pile is also better insulated, has more pockets for air and retains moisture more easily. The finer the pieces, the faster your compost will be finished.
   
   
3. Layer 15 cm (6 inches) of well-watered "browns" and 15 cm of "greens," mixing the two layers together.
   
   
4. Alternate and mix layers of each type of material, adding water as needed, until the pile is at least one meter (3 feet) high.
   
   Adding the material in layers simply helps you judge the right proportions of "brown" and "green." But everything should then be thoroughly combined to compost efficiently.
   
   
5. Cover the pile to protect it from heavy rain, and wait. The compost should begin to heat up within hours.
   
   To witness decomposition in action, you can stick a metal rod into the centre of the pile for a few minutes, then check if it has warmed up. Compost thermometers are available at garden centres, or you can mount a meat thermometer at the end of a stick, if you want precise temperature readings.
   
   Vapour emerging from aeration holes, and a fine grey fungus just under the surface, are other good signs of an active hot compost.

What if it doesn't heat up?

When a compost pile won't heat up, the problem is almost certainly one of three things: a) the pile is too small; b) it's too dry; c) it needs more "greens" or, especially in cold weather, a "starter" to give it more nitrogen.

Compost Activators

Garden suppliers sell compost starters or "activators," often composed of high-nitrogen fertilizers. In some cases, "inoculants" of dehydrated bacteria are also described as compost activators.

While high-nitrogen fertilizers may be helpful, the benefits of adding more bacteria from a package have yet to be proven. All the bacteria you need should already be present in the soil under the compost pile or the food and garden waste you add. You could try soaking ordinary garden soil in water for an hour and douse the heap with the teacoloured liquid. But giving a boost of nitrogen to the bacteria you already have is the best solution.

Fresh stable manure is the ideal compost starter, though it may be hard for some of us to find; harder yet to explain to your next-door neighbours. While the commercial activators based on high-nitrogen fertilizers do heat up the compost quickly, it's hard to control the amount of nitrogen added this way and the excess may leach out or escape as ammonia into the air.

There are several effective organic alternatives: bloodmeal, finished compost, or wellcomposted manure, for example. Or, you can simply rebuild the compost pile with additional grass clippings or other "green" materials.

The Hot Composting Timetable

The temperature of the pile should rise steadily, peaking between 50^oC to 65^oC (120^oF to 150^oF), 24 hours to one week later. When the temperature begins to drop, the compost is ready for turning. Break up any clumps of material, and move the outside parts to the base and centre. If the pile is too dry, this is the time to wet it. Cover the pile again, and wait.

The temperature should peak again in about a week, in a pile made of well-shredded materials. Remember, the smaller the pieces, the faster the compost. As soon as it begins to cool, turn the pile once more. In another week or two, the compost should be finished; that is, dark and crumbly, fresh-smelling, with very little of the original material identifiable. When compost is ready for use, the temperature of the pile won't rise above 43^oC (110^oF) no matter how often you turn it.