coffee containers (to
measure out proportion)
- wood chips
to go home
- food waste
living organisms have a Carbon to Nitrogen (C:N) ratio for their tissues.
For microorganisms, carbon is
the basic building block of life and is a source of energy, but nitrogen
is also necessary for such things as proteins, genetic material, and cell
Decomposition of organic materials in your compost pile is greatly
increased when you create the proper balance between the carbonaceous
because they are dry) and the nitrogen-rich materials (called
because they are more fresh and moist). This balance is referred to as the
and shown as C:N.
Microorganisms that digest compost need about 30 parts of carbon for every
part of nitrogen they consume. That's a balanced diet for them. If there's
too much nitrogen, the microorganisms can't use it all and the excess is
lost in the form of smelly ammonia gas. Nitrogen loss due to excess
nitrogen in the pile (a low C:N ratio) can be over 60%. At a C:N ratio of
30 or 35 to 1, only one half of one percent of the nitrogen will be lost.
That's why you don't want too much nitrogen (fresh manure, for example) in
your compost: the nitrogen will be lost in the air in the form of ammonia
gas, and nitrogen is too valuable for plants to allow it to escape into
A maximum of 35% of the carbon in fresh
organic material will be converted into soil humus IF there is
sufficient nitrogen present.
A minimum of 65% of the carbon in fresh
organic material will be given off to the atmosphere as carbon dioxide
due to microbial respiration.
The humus formed from the decomposition of
fresh organic material will contain approximately 50% carbon and 5%
nitrogen. In other words, the C:N ratio of the humus is 10:1.
Most fresh plant material contains 40% carbon.
The C:N ratio varies because of differences in nitrogen content, not
carbon content. (Note: Dry materials are generally in the range of 40
to 50 percent carbon, and sloppy, wet materials are generally 10 to 20
percent carbon. Therefore, the most important factor in estimating the
carbon-to-nitrogen ratio of plant or food waste is how much water is
Generally speaking, you can get C:N ratios of 30:1 to 50:1 by adding two
parts of a GREEN material to one part of a BROWN material to your bin.
A "part" can be defined
as a certain quantity of the material, such as two 5-gallon buckets of
GREEN and 1 packed bucket of BROWN.
Play with the chart below.
For example, food scraps, grass clippings and leaves come close to an
average of 30:1. How? Add-up the Carbon side of the ratio for all three
materials, i.e. 15, 17, 60, and divide by the number of materials, i.e.
three. 92/3 = about 31:1.
Aged Chicken Manure 7:1
Fresh manures are way to
hot and can burn your plants and roots!
One of the most important
ingredients for composting, especially shredded or broken down
Food Scraps 17:1
Straw, Hay 90:1
The best way to use is to
shred for faster breakdown.
Coffee Grounds 25:1
produced compost is high in sawdust or shredded bark chips.
Use very sparingly!
Grass Clippings - Fresh 17:1
Dry clippings would be
higher in Carbon. Therefore, use as carbon source if
Woody chips & twigs 700:1
Be sparing. Best use is
small material at bottom of bin or pile.
Fresh Weeds 20:1
Make sure you don't
compost weeds with seeds, unless you insure that your pile
gets hot - over 140°F/60°C.
Shredded Newspaper 175:1
Has no nutrient content.
Best used in vermicomposting. Always shred and soak in water
for fast breakdown.
Fruit Wastes 25-40:1
Nut shells 35:1
Rotted Manure 20:1
seeds that can sprout
Pine Needles 80:1
Use sparingly. Very
acidic, waxy; breaks down slowly.
Humus (soil) 10:1
This is nature's natural
ratio. Use sparingly in pile. Best used to
"seal" the pile by putting a 1-2 inch layer on top.
Corn Stalks 60:1
Shred or cut up in small
pieces for fast break down.
General Garden Waste
Peat Moss 58:1
Has no nutrient value,
1. Above information is just for teachers who want to understand more the
complex nature of making good compost. Remember compost is just one
component to make enriched soil. Soil is rocks plus organic matter.
Compost is organic matter.
2. Schedule a compost party. Send
parents a notice of what you are doing (flyer). This helps increase
their awareness of what experiment their students will be participating.
Types of food waste needed:
rotten or old lettuce, vegetables (raw or cooked), onion peels or other
vegetable parts that were to be thrown away
Fruit: peels or cores (example, banana peels, apple cores).
Whole fruit is ok but should be cut into smaller pieces.
, bread (parts of sandwich without meat)
BRING: (we cannot use these
for this specific experiment)
not bring MILK
Products (cheese, yogurt, etc)
Do not bring Meat
(chicken, fish, beef, etc) (egg shells are ok but no eggs themselves
Do not bring garden