Composting is the breakdown of organic material into a dark, soil-like material where none of the original organic materials can be identified. Most organic waste materials can be used to make compost such as husks, manure, effluent, vegetable and plant waste, stubble and so on can be used.
There are three types of composting
- Vermicomposting – using composting worms
- Passive composting – the natural and slow decomposition of plant waste
- Active or Thermophilic composting – the rapid breakdown of organic material using machinery, heat and water to sterilise seeds and pathogens.
The Benefits of Composting
There are many benefits of using composting. The main benefits are the addition of organic matter, and micro flora and fauna. The organic matter provides food for soil life and increases stability of the soil so it becomes more resistant to erosion and compaction and holds more moisture. The micro flora and fauna are important in the recycling of nutrients within in the soil ecosystem.
What’s a soil ecosystem?
Most of a farm’s life exists underground and out of sight. Billions of organisms inhabit the soil, breaking down dead organic matter and releasing the nutrients necessary for plant growth. MICRO-organisms like bacteria, actinomycetes, algae and fungi, MACRO-organisms include earthworms and arthropods such as insects, mites and millipedes. Each group plays a role in the soil and assist the farmer in producing a healthy crop.
Adding Compost also:
- adds natural organic carbon (C)
- protects soil from erosion
- increases soil structural stability
- improves moisture holding capacity
- increases water infiltration and reduces water run off
- adds nutrients (as slow release)
- encourages a wide range of soil organisms.
What You Need to Make a Good Compost ?
The rules of composting are widely known and the same whether you are making a small pile for your own garden or a large commercial windrow for commercial production. The key elements needed when making good active or thermophilic compost are.
The micro flora and fauna require air and by turning the pile regularly and include a range of different sized and shaped materials. BUT, remember that large pieces of woody material will take much longer to break down than smaller ‘chips’.
Ideally, water content when composting should be 50 to 60% (it feels like a damp sponge but no water comes out when you squeeze it with your fingers). To make sure the compost pile stays wet enough during the composting process you will need to apply water to keep moisture up to the pile.
Good compost must have a balance of carbon-rich brown material (Straw, hay, woody material) and nitrogen rich green material (green leafy matter or manure) materials, to make the correct mix of carbon.
The Carbon to Nitrogen Ratio
The Carbon to Nitrogen ratio can be determined easily when you know the C and N values and weight of the product you are using. To calculate the C:N ratio, divide the total carbon % of your selected materials—or ingredients— by the total nitrogen % of your materials. You can have as many materials as you like.
An area suitable for composting
You will need to dedicate an area for at least 8–12 weeks. The area you identify should be relatively flat and free of stones, tree stumps, drainage lines and weeds (especially bulbous weeds). You can make a good base for the compost pile using crushed road base, granite or blue metal dust. There should be enough room for machinery needed to turn the compost. The pile should be located so it will not contaminate adjacent land or waterways via wind drift and water runoff.
If making a large amount of compost, you will need a Compost Turner or other machinery to turn the pile. A front-end loader or excavator will let you get started. Alternatively, you may consider using a contractor.
You may need to cover your pile if there is excessive rainfall.
How Do You Create Good Compost?
Constructing a pile
Mix all materials and construct a pile that is between 1.5 and 2 metres high and 2.5 to 3.6 metres wide. It can be as long as you need. Every 1 metre in length will make about 4 cubic metres (m3) of compost at these dimensions. Add water so that the pile is wet through but not soaked. Check a sample of material from the pile; if it glistens with water but doesn’t drip excess water then it is wet enough.
Turning the compost pile
After about one week, check the temperature in the pile. It should be between 50 and 650C (this is now considered a thermophilic compost). Use a shovel to dig a hole in the middle of the pile. You will probably notice steam rising and the compost should feel uncomfortably hot. You can check the temperature accurately with a thermometer or a data logger, which transfers temperature information to your computer. If the temperature is right, turn your pile about seven days after measurement, or when the temperature starts to decline. If the temperature is above 70oC turn the pile immediately and reduce pile height to a maximum of 1.5m.
When turning the pile, ensure the materials from the outside of the pile are placed on the inside. This can be achieved by rolling the pile over using a front-end loader or lifting the pile and dropping in its original place using an excavator.
Monitoring the temperature
Keep monitoring the temperature on a weekly basis and turn the pile after the correct temperature has been reached each time. The pile will probably need to be turned at least three times before the compost is ready for use but may need up to six turns, depending on the materials used. Once the pile has stopped producing heat let it ‘cure’ for at least two weeks before use.
NOTE: It is very important for the windrow or compost heap to reach about 60oC to kill any pathogens, seeds and to break down all the material properly. However, It should not get hotter than 70oC as this will reduce the nutrient and carbon value of your compost and kill beneficial decomposer organisms.
When Is It Ready?
Good quality compost will take about 6-8 weeks if done properly heaver products like macadamia husk can take up to 12 weeks. It’s important not to use compost before it is ready as the oganic matter will still be nitrogen will have been temporarily taken by the decay organisms and be unavailable to plants.
Good quality compost that’s read to be used has the following characteristics.
- Temperature; the windrow or pile has stopped getting hot.
- Smell; a nice earthy smell, with no bad, sour or rotting odour.
- Feel; The feel will be moist and earthy, not wet and sloppy or dry and powdery
- Look; A rich dark soil sized where none of the original organic materials is distinguishable.
If you would like to know more the ACT Environment, Planning and Sustainable Development Directorate produces a 4 page publication by to provide existing or prospective operators of composting facilities with the background information when establishing a commercial composting operation. This guide is also a reference guide to the large volume of resources readily available and accessible.