4. Compost Bins

In a natural system there is no waste or pollution – the output from one natural process is always the resource for another natural process. Recycle and reuse local resources as many times as possible within a polycultural system.

Compost is plant matter that has been decomposed and recycled as a fertilizer and soil amendment. Compost is a key ingredient in organic farming. At its most essential, the process of composting requires simply piling up waste outdoors and waiting a year or more. Modern, methodical composting is a multi-step, closely monitored process with measured inputs of water, air and carbon- and nitrogen-rich materials. The decomposition process is aided by shredding the plant matter, adding water and ensuring proper aeration by regularly turning the mixture. Worms and fungi further break up the material. Aerobic bacteria manage the chemical process by converting the inputs into heat, carbon dioxide and ammonium. The ammonium is further refined by bacteria into plant-nourishing nitrites and nitrates.

The best solution is to build 3 wooden bins about 1 to 1,5 meters cube shape with cover and a front door with boards that can be added up to the top. We can also use wire screens if available.

All composting material is piled in first bin and then turn to the next bin after a few weeks. At last, it is turned to the last bin for final composting. Meanwhile, the first bin can be used to start a new pile.

Ingredients – Materials in a compost pile.

Composting organisms require four equally important things to work effectively:

  • Carbon — for energy; the microbial oxidation of carbon produces the heat. High carbon materials tend to be brown and dry.
  • Nitrogen — to grow and reproduce more organisms to oxidize the carbon.  High nitrogen materials tend to be green (or colorful, such as fruits and vegetables) and wet.
  • Oxygen — for oxidizing the carbon, the decomposition process.
  • Water — in the right amounts to maintain activity without causing anaerobic conditions.

Certain ratios of these materials will provide beneficial bacteria with the nutrients to work at a rate that will heat up the pile. In that process much water will be released as [evaporation|vapor] (“steam”), and the oxygen will be quickly depleted, explaining the need to actively manage the pile. The hotter the pile gets, the more often added air and water is necessary; the air/water balance is critical to maintaining high temperatures until the materials are broken down. At the same time, too much air or water also slows the process, as does too much carbon (or too little nitrogen).

The most efficient composting occurs with a carbon:nitrogen mix of about 30 to 1. Nearly all plant and animal materials have both carbon and nitrogen, but amounts vary widely, with characteristics noted above (dry/wet, brown/green). Fresh grass clippings have an average ratio of about 15 to 1 and dry autumn leaves about 50 to 1 depending on species. Mixing equal parts by volume approximates the ideal C:N range. Few individual situations will provide the ideal mix of materials at any point in time – in this respect, home composting is like horseshoes, perfect is great, but close still works. Observation of amounts, and consideration of different materials as a pile is built over time, can quickly achieve a workable technique for the individual situation.

Materials OK to use:

Nitrogen-rich materials

  • Grass clippings
  • Seaweed and aquatic plants (washed to remove salt)
  • Fruit and vegetable trimmings
  • Kitchen scraps like coffee grounds, egg shells, leftover
  • bread, rice, etc.
  • Fresh, leafy garden trimmings

Carbon sources

  • Chipped trees
  • Twigs, small branches from trees and shrubs (chopped)
  • Sawdust (from untreated wood)
  • Stems of fibrous grasses
  • Palm fronds (chopped or shredded)
  • Newspaper or white paper (shredded)

Undesirable materials:

May contribute pests (weeds, plant diseases) when inadequately composted

  • Weedy, persistent plants
  • Diseased plants

Human health hazard

  • Dog or cat feces, used kitty litter

May attract flies, rats, animals

  • Oils
  • Dairy products
  • Meat or bones of animals, poultry, fish

Are not biodegradable

  • Metals, glass
  • Rubber, plastics

Building a compost pile

This simple recipe for making a compost pile should produce ready-to-use compost in a few months.

  1. Accumulate enough materials for a pile at least 2 x 2 x 2 ft; or even better, to make a 3-ft cube.
  2. Shred or chop the materials to 1–2 inches in size to expose more surface area for faster decomposition.
  3. Start the pile with a 4–6 inch thick base of carbon source materials (dead leaves, wood chips, shredded paper, etc.). Moisten. Add a 2–3 inch layer of nitrogen rich materials. Food scraps may make up part of this layer. Continue to alternate and mix layers of nitrogen rich materials with carbon sources, adding water as needed. The pile should be about 3–4 ft high or, if in a bin, not more than 4–5 ft high. Close the bin or cover the pile with a plastic sheet.
  4. Inoculate a new pile, if desired, by sprinkling a small amount of topsoil or compost between layers. Some composters believe this speeds the process by “seeding” the new pile with decomposing organisms.
  5. Monitor moisture content; test by feeling a handful of compost and squeezing it as you would a sponge. It should feel moist without yielding more than a few drops of liquid. If the pile is too wet, turn it to allow air in and improve drainage. If the pile is too dry, water it and turn it.
  6. Periodically check the temperature in the pile’s interior. A compost thermometer is helpful, but you can estimate the temperature by touch. It should peak between 120° and 160°F (hot to the touch). When the temperature begins to drop, turn the pile and rotate materials from the outer and top parts of the pile toward the base and middle; move the more composted middle part to the outer part of the pile. For easy turning, use a garden fork to shift the compost to a second bin; the material at the top will now be at the bottom. In the process, you are aerating the pile, and you can add water if the pile seems to be dry.
  7. Continue to monitor the temperature in the pile. It should heat up again. After the temperature peaks, turn the pile once more. You may note that white molds decrease over time, insect populations will change, and beneficial worms become abundant as the compost matures.
  8. The process is completed when the pile does not generate any more heat. When the pile is cool and the compost has aged for another four weeks, it should be finished. The pile should be much smaller than its original size, and the original materials should no longer be recognizable. The compost should be dark, loose (crumbly), and without any strong or unpleasant odor.
  9. Use the compost to mix into the soil or to make compost tea to use for watering crops, seedlings, and starts. Spread compost on your lawn and under shrubs, flowering plants, vegetables, and trees.

Helpful hints

  • Chop or shred leaves, twigs, and other materials to speed composting. Smaller pieces of organic material “cook” faster than larger pieces because more of the material surface is exposed.
  • A compost pile needs the right mix of materials to decompose quickly. When building the pile, try to have at least one part nitrogen-rich materials for every two to three parts carbon sources. You may need to experiment with different materials and proportions to develop enough heat for rapid decomposition.
  • Balance moisture and aeration to develop heat; too much of either results in a “cold,” inactive pile. The hotter the pile, the faster the composting process. Temperature of an actively composting pile normally range from 120 to 150°F. Higher temperatures (140–160°F) kill harmful pathogens, insects, and weed seeds. Avoid turning the pile too often, because the heat is lost whenever the pile is turned. Turn it immediately, however, if an odor develops; the smell should fade away.


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