I am having a hard time digging up how much of raw dry mass of leafs gets converted into the compost.

To put in some numbers, lets say you have 100kg of dry leafs, how much of compost will you get out?

  • I can't tell you in numerical terms, but what I can say is, think of an average sized black plastic bin liner - if you crammed it to the top with wet or damp dead leaves, tied the top shut and left it for a year or two, you'd find a quantity of black soil like material in the bottom of the bag, probably about an average to large sized bucketful. In other words, they shrink down eventually to not very much. They should be wetted before bagging up if they're not wet already. – Bamboo Apr 30 '17 at 10:54
  • Thanks! Yes, the volume is reduced drastically, but I wonder if mass too. – sanjihan Apr 30 '17 at 11:34
  • Why does it matter what the mass is? – Bamboo Apr 30 '17 at 12:36
  • Go by weight. After decomposers do their thing there is a loss of water, CO2, but the weight should stay close to the original. The volume obviously greatly reduced? After decomposing the original ingredients and chemistry is so changed as to be non recognizable. Take for instance my FAV mulch/compost. Human poo and sawdust. When decomposed properly it looks, smells, and is impossible to tell what the original ingredients were. Smells and looks beautiful, fine texture, dark taupe. Lots of nitrogen despite all the decomposing. Heavy metals are the only drawback. – stormy Apr 30 '17 at 19:04
  • @Bamboo What do you mean by 'wetting before bagging'? – stormy Apr 30 '17 at 19:05

The Louisiana Cooperative Extension Service advises:

During composting, the microorganisms consume oxygen while feeding on organic matter. Active composting generates a considerable amount of heat, and large quantities of carbon dioxide and water vapor are released into the air. The carbon dioxide and water losses can amount to half the weight of the initial organic materials, so composting reduces both the volume and mass of the raw materials while transforming them into a beneficial humus-like material.

However if dry leaves are kept dry they won't compost, so relative to dry leaves you may end up with much the same weight as you start with (the added water being most of the weight that is lost).

  • During decomposition, microorganisms consume O2 and needs lots of nitrogen. CO2 is fairly weightless, water is the one thing that leaves and takes weight of the entire kit'nkaboodle away. Dry leaves still have lots of moisture grins. Decomposed matter is what feeds the soil organisms (other than the decomposers) NOT undecomposed organic material. To decompose, one has to have air, a little moisture, nitrogen. If one put all the leaves and other organic material into a 'blender' to chop it up into teensy tiny bits, it would be faster and closer to the end result. – stormy Apr 30 '17 at 21:20

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