Essential Conditions for Good Composting

Airing - Oxygen (O2)

  • Porosity - 25 to 35% of its volume in air
  • Crushing of materials - a pile must have a structure that allows good ventilation; pieces that are too large do not allow for good surface contact and delays decomposition.
  • Organic Matter (OM) is preferable (straw, sawdust, stalks ...) Microorganisms need O2 to be able to oxidize OM (aerobic)
  • In the absence of O2 there will be anaerobic fermentation, with the formation of a bad smell (smell of ammonia - loss of nitrogen (N) in gaseous form and methane - loss of carbon (C) in the form of methane (CH4)), giving rise to a product that is not compost
  • The pile should be mixed
  • Do not compress the pile
  • Do not add excess water
  • Size of the pile (base 1.5 to 2m and height 1.5m)
  • Very large size makes it difficult to handle the pile and ventilate the interior


Humidity - 55 to 65% of its weight in water

  • The pile must always remain moist (microorganisms need water) but excess water prevents air circulation. To check the amount of water, squeeze the pile a little and drain no more than 2-3 drops between your fingers.
Essential Conditions for Good Composting




  • Must not exceed 65-70ºC. The temperature should be lowered by watering, turning or introducing OM with a higher C/N ratio into the pile. Use appropriate thermometers or an iron rod inserted into the pile.


Initial Organic Matter

  • Adequate C/N ratio - must be between 25-30 OM that is highly woody (pruning firewood, wood chips, straw) and has a high carbon content.
  • In a pile based on woody material, we must mix in green material, animal waste, or even nitrogenous organic fertiliser to accelerate the decomposition (increase temperature)
  • Microbial activators (commercial versions already exist)
    • Yeasts based on nettle plants, feverfew, pine bark, milefolium, mackerel and comfrey
    • Bacteria and enzymes
    • Biodynamic preparations
  • A pile must have a structure that allows good ventilation (but not too much)
  • Pieces that are too large do not allow for good surface contact, delaying decomposition
  • We must break-up the OM before placing it in the pile - for example, the vine sticks should be reduced to pieces of 3-5 cm
  • There are materials with such a favourable structure that they are called structuring OM


Composting Location

  • Sufficient area to facilitate turning and mechanisation
  • Easy access
  • Location sheltered from winds
  • Shade or semi-shade during the summer; in winter avoid shading