The lowdown on composting

A few weeks ago I audited my compost, but I neglected to say why composting is so important. The food just compost’s in landfill right? Unfortunately this is not quite true. What really happens is the food scraps are left to suffocate. They get trapped inside plastic bags, hidden under junk and then squished, taking away all the oxygen. But microbes slowly break down the food scraps anyway (this is called anaerobic conditions – without oxygen, aerobic = with oxygen… I literally just made the link to why exercise is called aerobics). Because of these conditions, during the breakdown, methane (CH4 – same as cow farts) is released into the atmosphere. Methane, give or take, holds about 25 times more heat than carbon dioxide (CO2), this is very bad news for global warming!




These are very high-tech diagrams with real gases being emitted.

On top of that, when our food scraps breakdown in landfill they combine with heavy metals and chemicals from electronic waste, creating toxic sludge. This sludge is seeping into the ground and even into our water supply as we speak! This is a great incentive to dispose of your batteries the right way too!


This diagram is using CO2e which is carbon dioxide equivalent. Source:

In a compost heap or bin the decomposition of organic matter is accelerated. Bacteria, fungi and micro-organisms living in the heap break down the organic matter. A compost needs oxygen because those little critters (aerobic micro-organisms) need oxygen to survive. A compost also needs carbon to supply them with energy and nitrogen to supply them with protein. Think of them as teeny tiny body builders. Instead of releasing large amounts of methane (like food that’s sent to landfill), your little compost heap releases carbon dioxide (CO2). But wait… isn’t that the nasty little cousin to methane? Yes, however, when carbon dioxide is released in this form it is biogenic, not anthropogenic. Methane is much worse for climate change than carbon dioxide. We all need a certain balance of greenhouse gases in the atmosphere to survive, to keep us warm. The problem we’re having now is, because of human activity, we’re tipping the scales in the wrong direction. The science of composting is actually far more complex than my layman explanation but I’m not a chemist and I won’t pretend that I fully understand it myself! If you’re wanting to know more about the science, I got a lot of insight from Planet Natural Research Centre.
Compost in Australia:

  • About 3% of Australia’s human induced greenhouse gas emissions are generated by organic matter rotting in landfills
  • 4.5 MILLION tons of food waste end up in landfill every year… that’s the same as 26,000 blue whales!
  • About 45% of kerbside rubbish in Australia is compostable

Why composting is awesome:

  • Composting reduces waste ending up in landfill
  • By reducing kerbside waste we are effectively taking more trucks off the road, sparing even more fossil fuel consumption
  • Reduces your carbon footprint
  • Makes worms happy
  • Improves soil quality
  • Saves the need for artificial fertilisers
  • Decreases the amount you need to water your garden
  • Improves your garden

Types of compost

  • Tumbler – theses are a great choice if you have a bit of space as you can aerate the compost easily and helps it to decompose quicker. They’re elevated so really good at deterring pests. The downside is, when they’re full they can become quite heavy to move and you have to wait before adding more compost
  • Bin – these are neat, tidy and easy to use. They’re usually a bit cheaper than a tumbler and often have a trap door at the base to access the humus
  • Open heap – good for really big spaces and easy to get started. Literally just start lumping your compost in a heap. They do need a bit of help aerating and are more likely to attract pests
  • Bokashi bucket – this is an anaerobic system. Good for apartments and easy to use. Being anaerobic they tend to smell when you open the lid and they still produce methane, but they are a great way of diverting cooked food and meat from landfill. I have chosen to try one in our home (as mentioned in my compost audit) as toddlers are fickle creatures, particularly when it comes to food. Unfortunately not all of it can be saved and I’d rather it end up in the garden (eventually) than landfill
  • Worm farm – harder than the others as you have a new objective… keeping the worms alive (which I failed at… miserably)! As long as you maintain the correct balance of food and temperature you should have no troubles

Tumbler, bin, heap, Bokashi bucket and worm farm.

Now we know WHY we should compost, lets talk about HOW to compost (using a standard bin).

As I said earlier, a compost needs oxygen, nitrogen and carbon for it to breakdown better. So along with your food scraps you need to add a mix of the following:
Nitrogen (greens):

  • Grass cuttings
  • Food scraps
  • Tea leaves
  • Coffee
  • Manure
  • Weeds and fresh plants

Carbon (browns):

  • Straw
  • Dry leaves
  • Cardboard
  • Paper
  • Crushed egg shells
  • Twigs and stems
  • Saw dust (untreated timber)
  1. Each time you add a layer of nitrogen, add a layer of carbon
  2. To add in oxygen make sure you turn it with a pitchfork or similar at least once a week.
  3. If it’s dry add a little water or more greens
  4. If it’s too wet add more browns
  5. By keeping the right balance of greens, browns and oxygen your compost shouldn’t smell
  6. Avoid adding any cooked food, meat or dairy to keep pests and vermin away
  7. If it’s starting to fill up, the bottom layer should be ready to use on your garden. A lot of bins have a little trap door at the bottom so you can sneak the humus out to place around your garden.


Handy little diagram taken from ‘Practical Self Sufficiency’ by Dick and James Strawbridge.

There you have it! I hope this post has inspired you to start composting at home!

But wait there’s more… and here’s the really exciting part! The City of Melbourne operates the Compost Revolution, where you can get up to 80% off a new compost bin through your local council. So if you’re looking to start a compost or worm farm check it out to see if you can get a discount. We bought our current bin secondhand from Gumtree so it might be worth a look online too.

Happy composting,

Minimal Sam


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