Biogas - Carbon Nitrogen Ratios

Carbon - Nitrogen ratios for biogas produced from various raw materials. Reference table showing C:N ratios for different organic waste sources used in anaerobic digestion.

SourceCarbon - Nitrogen Ratio
Alfalfa hay18 : 1
Bagasse from sugarcane or sorghum stalks150 : 1
Chicken manure25 : 1
Clover2.7 : 1
Cow dung25 : 1
Cow urine0.8 : 1
Grass clippings12 : 1
Kitchen refuse6 - 10 : 1
Lucerne2 : 1
Pig droppings20 : 1
Pig urine6 : 1
Potato tops25 : 1
Sawdust200 - 500 : 1
Seaweed80 : 1
Straw60 - 200 : 1
Sewage sludge13 : 1
Silage liquor11 : 1
Slaughterhouse wastes3 - 4 : 1

Important Note

When the Carbon Nitrogen ratio exceeds approximately 30, biogas production diminishes. This is an important consideration when selecting raw materials or blending feedstock for anaerobic digestion systems.

About Biogas

Biogas is a mixture of gases produced by anaerobic (absence of oxygen) bacterial breakdown of organic matter. Biogas can be produced from raw materials such as:

  • Agricultural waste
  • Manure
  • Municipal waste
  • Plant material
  • Sewage
  • Green waste
  • Food waste