About compost making

The most important gardening activity is compost making. No matter what type of soil you have, garden compost improves soil condition and enables you to grow more successfully. I’m still amazed at how much lighter my soil becomes after working in garden compost.

But if you want info. on making your own seed / potting compost click here.


Here I explain how compost making works and outline the compost making process. These 2 links compare design and use of tumbler and static compost bins and look at practical issues.

Composting happens when mico-organisms, fungi, bacteria, and small animals, digest organic matter. It is a biological process.

Composting requires: - air, moisture (but not lots of water), warmth, organic matter and micro-organisms.

Decomposition goes through a sequence, with pioneer micro-organisms (e.g. sugar fungi) paving the way for a sequence of cellulose strippers and others.

While the pioneers grow at low temperatures, if conditions are right they are followed by organisms that grow at higher and higher temperatures.

Composting releases nutrients from organic matter and produces humus. The black humus holds lots of water and nutrients.

Composting genterates heat as a bye-product. Insulate the heap against heat loss. Hot green heaps kill weed seeds and disease.


This breaks natural protective layers: wax, cellulose, fibres and lignin. So access to micro-organisms is vastly increased. This increases the speed of decomposition.

Small shredded pieces provide better insulation against heat loss and reduce water loss.
Find more on garden shredders here

The tougher brown matter increases aeration and reduces excess water.

A balance of nitrogen rich sappy green stuff and carbon-rich tougher brown organic matter should be mixed together.

Hot And Green Compost Making
And The Batch Process

  • Fast composting is done by including a higher proportion of sappy green matter with higher nitrogen content (lower Carbon/Nitrogen ratio) e.g. grass cuttings, cabbage leaves, poultry manure, for example.
  • When the heap is largely at the same stage of decomposition it provides the maximum food and maximum growth of micro-organism.
  • Caution - too much green matter gives a mushy paste. This reduces oxygen diffusion causing anaerobic decomposition (without oxygen). This produces unpleasant odours. Brown material: straw, paper etc... mops up water.
  • Making compost in batches is the traditional method with hot heaps. First gather material, then make the heap. Open compost bins need about 25 cubic feet (0.7 m3) of organic matter to generate sufficient heat.
  • Finely shredded material plus regular turning of the heap increases aeration, insulation and speeds composting.
  • A temperature 55oC - 65oC, often only achieved at the centre, will kill weed seeds. Incidentally, the heat produced is a by-product of the decomposition process.
  • Hot composting kills plant pathogens, but also kills organisms that protect seedlings from disease attack.
  • Nitrogen rich effluent sometimes drains from green matter but the EnviroCycle tumbler compost bin is able to collect and save this compost tea as well.
  • Hot green compost is relatively weed and disease free. The available nitrogen means it is best used to improve fertility.

Advantages To Compost Making In Re-Cycled Plastic Bins

  • Tumbler compost bins enable green heaps see above to be composted speedily with smaller volumes. Ideal for small gardens. Click link for more...
  • Static plastic bins enable continuous compost making with small amounts, as and when available (e.g. small lawn or kitchen waste...). No batch making. Smaller sizes are less reliable at reaching high temperatures - click link for advice.
  • Plastic compost bins speed up brown heaps compared to traditional methods. Brown compost making is described below.

Slow And Brown Compost Making

garden compost

Moisture retentive garden compost
  • With higher proportions of brown material e.g. shredded hedge cuttings, tough fibrous plants; or when small amounts of organic matter are available at one time, you will probably have a slow compost heap.
  • You add to this gradually over the season probably building it up in layers.
  • You can alternate green and brown layers and suitable micro-organisms will breed in each layer.
  • Brown layers will tend to be more open and help to aerate the heap reducing the need for turning.
  • I usually include thin soil layers to introduce microbes and help bind any nutrients that might leach out.
  • Brown heaps won’t get steaming hot and probably won't kill weed seeds or pathogens. You can eliminate weed seeds by a ‘stale bed’ method in storage, or seeds may be killed after germinating inside the heap.
  • Earthworms and tiny animals populate cool heaps. They make nitrogen rich droppings.
  • Fungi will probably play a greater role in decomposition of cool heaps and fungi can make humus. Brown heaps may produce more humus than green heaps.
  • Humus holds lots of water and holds nutrients more effectively than clay. Overall garden compost is a great soil conditioner.
  • Studies have shown that brown compost contains micro-organisms that protect seedlings from plant pathogens.
Although layers of soil help to introduce microbes, proprietory compost activators deliver a larger dose and they introduce high temperature decomposers.
Compost making activators U.S.A.
Compost making activators U.K.

Comfrey, nettle leaves, urine and dried blood have all been used as activators.

HEAP AT THE BOTTOM OF THE GARDEN - Check out practical compost making methods on the links below




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