Updated: Apr 4
First we need to understand what is compost and why to use it. Compost is made by decomposing organic matter into black crumbly material.
Shop bough compost might not be the real thing and often shouldn't be even called that way. For example peat based or current alternatives as coir based composts are not going through composting process, are nutrient poor and sterile, therefore chemical slow release fertilizers are added. As such they should be call growing medium not compost.
Homemade compost is the "black gold" for gardeners as it feeds not just the soil with nutrients but more importantly its high in organic matter, bacteria, fungi, worms and many organisms. It is main ingredient for organic gardening and basic building block for all terrestrial life on earth.
There are 2 composting styles:
is decomposition that occurs using microorganisms that do not require oxygen to survive. In an anaerobic system the majority of the chemical energy contained within the starting material is released as methane.
Pros: easy set up, no need to turn the heap just keep piling organic waste
Cons: takes12-18 months, its harder to control, can dry out in summer or get soggy in winter, produce methane that is 83x more potent greenhouse gas than CO2
is decomposition of organic matter using microorganisms that require oxygen. The microbes responsible for composting are naturally occurring and live in the moisture surrounding organic matter. As aerobic digestion takes place the by-products are heat, water and carbon dioxide (CO2)
Pros: fast composting in 4-6 months, easy to control variables such as heat and moisture, more eco-friendly due to less greenhouse gasses
Cons: more labor intensive due to turning heap every 2-3 weeks
Achieving best compost
You can set up compost anytime but in winter the process slows down, grass clippings are great compost activator as they are high in nitrogen and heat up the pile so spring and summer is best. Alternatively you can buy some compost activator.
Whether you turn or don't turn the compost heap follow few simple rules:
- mix brown and green organic material 50/50
- pile green and brown organic waste lasagna style
- chop up waste material to increase surface area and speed up decomposing
- maintain the heap moist but not soggy
Brown material is high in carbon- pieces of brown cardboard, dry hay/grass, twigs, wood chipping, coffee grains
Green material is high in nitrogen- kitchen waste, grass clippings, garden green waste
1 bay system
Good for anaerobic heap, just pile organic waste on top and take ready made compost from the bottom.
Multi bay system
For turning style best is minimum of 3 bay system, 4 or 5 if you have lots of space. Pile fresh organic waste in bay 1, when full turn it into bay 2, then into 3 and so on starting new pile in bay 1 each time. You can regularly turn heap back and forth
between bins to speed up decomposition.
There has been surge of new type of hot-bins on the market. They are made of highly insulated material to produce high heat that speed up composting. This is only compost system where you can add some animal based food waste.
They have advantage of taking up small space and give fast result, however this comes at a price and are very expensive. You will also need to regularly add starting culture each time which is additional cost that you need to keep in mind.
or wormeries is composting with the help of specialized worms. These are single or multi-tray systems where the worms eat up the organic matter and turn it into rich humus-like material known as vermicompost. They are small, do not smell and you get additional benefit of worm tea which you can use diluted as liquid fertilizer.
is composter with rotating feature. The idea is to have combination of 1 bay system with the benefit of multi-bay system where you turn compost and speed up decomposition. However I have read reviews that this system is bit messy as it leach out the liquids and when full its very hard to turn.
When is compost ready?
This can be bit subjective matter depending how fine you want the compost to be, but most important is that you can`t see any original waste that went in, it will be black, crumbly and does not smell bad. If there are little twigs and compost its bit coarse you can choose to sieve it. I`m sieving compost only for small pots when I need to pot up some plants or plant seeds, otherwise I spread the compost as it is on my veg beds taking out only the largest pieces that will go to new compost pile.
Follow us on
Grow It Bio page
Organic Gardening Ireland chat group