Organic Waste Recycling

98 Organic waste recycling: technology and management

Table 3.1 C/N ratio of various wastes

Materials Nitrogen

(percent of dry weight)

C/N ratio

Nightsoil 5.5 - 6.5 6 to 10
Urine 15 - 18 0.8
Blood 10 to 14 3
Animal tankage - 3
Cow manure 1.7 18
Poultry manure 6.3 15
Sheep manure 3.8 -
Pig manure 3.8 -
Horse manure 2.3 25
Raw sewage sludge 4 to 7 11
Digested sewage sludge 2 to 4
Activated sludge 5 6
Grass clippings 3 to 6 12 to 15
Nonlegume vegetable waste 2.5 to 4 11 to 12
Mixed grasses 2.4 19
Potato tops 1.5 25
Straw, wheat 0.3 to 0.5 128 to 150
Straw, oats 1.1 48
Saw dust 0.1 200 to 500
From Golueke (1972); reproduced by permission of the JG Press

• Some of the C substrate such as cellulose and lignin are highly resistant to
  biological break-down, and are only decomposed over a long period of
  time.


• Some of the nutrients such as keratin-type proteins are in the accessibly
  difficult form and is not easily available during much of the composing
  process.


• Some nitrogen fixation can take place through the bacteria Azotobacter
  sp. especially in the presence of adequate phosphatic material.


• Analysis of C concentration may be difficult and the following
  relationship providing an accuracy of within 2-10% is proposed (Gotaas
  1956):

100 - % ash

% C = (3.6)

1.8