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How to Make Compost

Compost is the end product of controlled decay. A modest collection of leaves, grass clippings, kitchen scraps and garden leftovers yield dark, rich humus. Humus is a source of nutrients for soil organisms and plants making it the best soil-builder and conditioner.

There are many different methods of composting but the basis behind making compost are the same. Heap ingredients into layers, making sure the resulting pile gets the proper amount of air, moisture and materials needed to maintain the right temperature. The pile will need to be turned over (mixed up) to keep the composting process going and to speed up decomposition.

Under ideal conditions, with a little extra effort you can produce compost in as little as 2 to 3 weeks. There are several important factors essential for producing compost quickly.

SIZE of Materials

  • materials ½ - 1½" in size decompose best as this creates more surface area for hungry micro-organisms to feed on. The more organisms that can be supported, the faster the compost will be produced
  • hard and woody materials need to be chopped / shredded into small pieces
  • soft, succulent materials don’t need to be chopped up as small
  • leaves should be shredded - easily done with a lawn mower

Carbon to Nitrogen Ratio

Compost requires plenty of oxygen, along with the right mix of ingredients, to keep decay-causing organisms going strong. These micro-organisms need carbon (for energy) and nitrogen (for reproduction).

In order for a successful composting pile the mixture of materials in the pile should have a carbon to nitrogen ratio of 30 to 1. A pile with that balance of material will rot steadily and will yield nutrient rich compost. How do you know what your pile’s ratio is? Dry materials are in the range of 40-50 percent carbon, sloppy wet materials are generally 10 to 20 percent carbon. Here is a chart of C to N ratios of common compost ingredients:

To calculate your carbon to nitrogen ratio use the chart to find the approximate percentages of carbon and nitrogen in your ingredients.
% Carbon = % carbon per ingredient X # of parts of that ingredient
Then add up the total carbons of each ingredient
% Nitrogen = % nitrogen per ingredient X # of parts of that ingredient
Then add up the total nitrogen’s of each ingredient
Divide the carbon by the nitrogen and get the C: N ratio. A ratio between 25 and 35 is ideal for decomposition.

Moisture Content

Composting works best with a moisture content of 50% - moist but not soggy. Too much moisture slows decomposition and produces an unpleasant odour due to the activity of methane producing micro organisms. Conversely if the pile is too dry decomposition will be very slow or may not occur at all.

Heat

Heat is supplied by the respiration of micro organisms as they break down organic matter. Heat retention is best in bins versus open piles and even better in covered bins versus uncovered bins. High temperatures favour the micro organisms that are the most rapid decomposers. These micro organisms are most active with temperature around 160ºF (71ºC) and a well built compost pile can maintain that constant temperature.

Turning

Compost piles need to be turned to prevent over heating and to aerate / mix materials. If the internal temperature of the pile exceeds 160ºF (71ºC) the necessary micro organisms are killed, the pile cools and the process must start over. When turning the pile move material from the outer edges into the center of the pile. This ensures that all materials reach optimal temperatures at various times.

Compost maturation

  • turning every 1 to 2 days compost should be ready in 2 to 3 weeks
  • the less you turn the pile the longer it will take
  • once a pile is started do not add any additional materials as this will lengthen the decomposition time of the whole pile
  • Nothing needs to be added to organic materials to make them decompose. The micro-organisms active in the decomposition process are present on plant materials and develop rapidly in the compost pile

Problems

  • A pile should heat up to high temperatures within 24 to 48 hours. If it does not: the pile may be too wet - materials should be spread out to dry
  • too dry - add water until the pile is evenly moist
  • not enough green material - in the pile is neither too wet nor too dry then the nitrogen level is too low. This can be corrected with addition of high nitrogen materials - grass clippings, fresh manure.

When the carbon to nitrogen ration is less then 30 to 1, organic matter decomposes rapidly but a loss of nitrogen occurs producing an ammonia gas. If an ammonia odour is present it means valuable nitrogen is being lost in the air. To counter this loss add some high carbon materials to the pile.

Ingredients to avoid

Meat, bones, fatty foods (cheese), salad dressings, cooking oils, plants that are diseased, manure from meat-eating animals and wood ashes.

Healthy Compost Piles

  • pleasant odor
  • heat being produced
  • growth of white fungi on decomposing organic matter
  • reduction in volume of the pile
  • materials changing to dark brown
  • As the composting process nears its completion the temperature of the pile will drop until finally there is little to no heat being produced, signifying that the compost is ready!

Composting process will

  • kill many organisms that cause diseases
  • insects and insect eggs will not survive composting process 
  • most weeds and weed seeds are killed

Advantages to composting

  • create a valuable soil amendment
  • reduce waste being sent to landfills

 

Material /Ingredients

Carbon %

Nitrogen %

Alfalfa

13

1

Alfalfa Hay

12

1

Blood meal

3.3

1

Coffee Grounds

25

1

Cornstalks

60

1

Fresh Manure, cow

20

1

Fresh manure, horse

35

1

Fresh manure, chicken

7

1

Fruit Wastes

35

1

Grass Clippings fresh

15

1

Kitchen Scraps

15

1

Leaves

40-80

1

Legume - Grass Hay

25

1

Oat Straw

80

1

Paper

170

1

Rotted Manure

20

1

Sawdust

500

1

Straw

80

1

Vegetable waste, leafy

10

1

Vegetable waste, starchy

15

1

Weeds, fresh

10

1

Wood

700

1