There are many styles of compost making. Over the years, I have developed a set of procedures that are simple and effective for my Colorado environment. Making compost is similar to cooking: you start with a basic recipe and then adjust it to your specific situation. The basic compost ingredients are: organic materials, air, water, microbes and heat.
Containers and Pile Size
- Compost Bins: The optimum size for a pile and container is one cubic yard: 3 ft. x 3 ft. x 3 ft. The simplest containers are 3-sided bays made of plywood with removable front pieces. Two or three bays make turning easier.
- Locate the container in a moderately shady location such as under a tree.
- Always keep the pile covered with a plastic sheet or tarpaulin.
- In a dry climate, do not use a container with air holes. The pile dries up quickly.
- In a wet climate, allow air to circulate but still keep the pile covered.
Materials
- Compost ideally requires raw materials with a carbon/nitrogen ratio of 30:1 by weight. In practice that looks like approximately equal volumes of brown (carbon) and green (nitrogen) materials.
- Brown material = all dry woody stuff: stems, hay, straw, old leaves, egg boxes, wood chips and sawdust, unbleached paper towels, old compost, etc.
- Green material = all fresh damp organic stuff: grass clippings, green plants, table scraps including meat and dairy, kitchen waste (coffee grounds, peelings, refrigerator leavings), animal manures (not dogs or cats), etc.
- If the pile looks too brown or does not heat up, add supplemental nitrogen in the form of fish fertilizer, alfalfa pellets, and/or animal manures.
- Shred, grind or chop all organic materials into small particles. Use a chipper-shredder if available.
- Layering differing materials works, but shredding and mixing all materials is easier, quicker and more effective.
- Gather material to make a pile that is a minimum of 3 ft. x 3 ft. x 18 ins.
- Adding minerals such as small amounts of wood ash (limited amounts), lime, bone meal, etc. creates excellent nutrients in the compost.
Air
- The microbes in a compost pile are aerobic and require oxygen to propagate. Keep piles dense and contained, but with small air pockets.
- To little air (too much water or nitrogen) creates anaerobic conditions causing slimy, smelly piles. Loosen and turn the pile with a fork to let air in.
- Too much air creates loose piles with empty spaces that never heat up. Compact the pile by chopping up the material and tamping it down.
Water
- The optimum moisture content is 50%-60% by weight; this feels like a damp but nor soggy sponge. Microbes need water to reproduce and move around.
- Piles with porous brown material need more watering to start. Piles with more wet green material need less water.
- If the pile looks soggy, add more brown material, loosen and turn with a fork.
- Surround the pile with the plastic sheet or tarpaulin if there is a chance it will dry out.
Microbes and Heat
- Under good conditions compost goes through 3 phases: the pile heats up to around 150F over 2 – 3 days; the pile stays warm for 1 – 2 weeks; the pile cools down and continues to degrade over a longer period.
- To optimize microbial life, inoculate the pile with compost tea, work castings or Alaska humus mixed in well.
- Insulate the pile with old blankets, comforters or carpet to keep the heat contained.
- Some pile may get very hot (170F) and start steaming. Turn the pile after 7 – 10 days to mix materials and adjust the temperature.
- Allow the pile to cool down for at least 2 weeks before using. Worms, insects and microbial life will continue to decompose the compost for months.
- Turn the cool pile as necessary to keep the compost texture uniform.
Now you have the most beneficial material for your soil — rich in humus, microbes and nutrients. Use it everywhere.