Learning how to compost at home is so good for your garden, your soil, the veggies you’ll grow – and the health of our planet.
And you can set up a compost system in almost any situation, whether you have a big backyard, a balcony garden or even just a few pot plants.
But getting started can seem a bit daunting. So let’s demystify the whole situation – and we’ll have you creating great home compost in no time.
First up – let’s answer a simple question: what is compost?
What is compost?
Well, compost is a process of actively feeding a huge number of microorganisms the right stuff in the right amounts, so that they munch and breed and munch some more, converting your pile of food scraps, paper, gardening prunings, manure, autumn leaves and whatever else into a nutrient-rich humus that we all know as ‘compost’.
Added back onto your veggie beds, compost improves your soil and thus everything you try to grow. And all from ‘waste’ resources freely available to you. So good!
So, let’s dive into the good dirt on composting – we’ll cover which bin is the best, what goes into your compost and what to avoid, troubleshooting tips for when things go a bit pear-shaped (we’ve all been there), and heaps more…
The problem with food waste – and how composting offers a solution
Food waste is a really big problem worldwide. It starts where the food is grown, where up to 25% of all vegetables produced don’t leave the farm.
Once the food gets to us, far too much is simply thrown away. In Australian households, we throw away about 3.1 million tonnes of edible food every singly year. That’s a lot.
And, sadly, too much of that binned food goes straight to landfill – where it rots and becomes anaerobic. At this point, the organic material is turned into the greenhouse gases methane and carbon dioxide (see illustration above) – and, unfortunately, methane is 25 times more harmful to our atmosphere than carbon dioxide.
Food waste also causes issues with odour, leaching, attracting vermin, and is a potential source for disease. This is where we composters can make a big positive impact.
The benefits of composting at home
Compost = healthy soil, healthy food, healthy humans, less food waste – and it assists with carbon sequestration, too.
How does composting lock up carbon in the soil? Well, firstly, compost creates humus which consists of long chains of carbon atoms that last a long time in the soil. Secondly, when compost is added to soil, the soil becomes healthier with improved structure and increased biological activity.
Therefore, the plants growing in it become healthier too and their capacity to photosynthesise is increased, meaning they’re capturing and sequestering more carbon from the air and storing it in the soil.
And then we get to eat the healthy food from the healthy soil, and with the food scraps, we can make even more compost.
Hooray. What an amazing closed-loop system!
Ingredients: what to put in your compost bin
OK, so we’ve convinced you to become a composter, yeah?
Before we help you decide which compost bin is right for your system, let’s first take a look at what can go inside your bin. Because there are all sorts of systems, techniques and recipes to make amazing compost, but all have four ingredients in common:
- Carbon materials: Dry and brown materials including straw, dead leaves, shredded office paper or newspaper with soy-based inks (no glossy paper), sawdust and cardboard.
- Nitrogen materials: Fresh materials including food waste, green grass clippings, some animal manures and seaweed.
So, you really only need to understand two key things: which carbon and nitrogen materials are safe to put in your home compost, and then how to mix them up at an appropriate ratio to keep all those compost microorganisms happy and munching away at your pile.
Which food scraps are safe to put in my compost?
Just about all food scraps can be used as a valuable source of nitrogen for your compost bin, tumbler or bokashi bin, but there are a few things to avoid. Let’s break it down.
Food scraps that can safely go into your compost:
- All fruit and vegetable scraps
- Crushed eggshells
- Small amounts of meat (without big bones)
- Cooked leftovers
- Coffee grounds and tea leaves
- Small amounts of cooking oils
Top tip: Make sure you chop up food waste so it’s the size of a 20-cent coin to accelerate the composting process.
Food scraps to avoid putting in your compost:
- Wood ash from your fire is an alkaline material. Sprinkling in a small amount is fine, but be careful not to add too much – it can make your compost too alkaline for general food production (which mostly desires a neutral ph of 6.5).
- Large bones take a long time to break down. instead, burn them in your wood fire.
- Citrus skins – a few is OK, but too many will make your compost too acidic.
- Teabags – many contain polypropylene plastic to keep the tea bags from falling apart. Find a plastic-free brand or use loose leaf tea instead.
Which carbon materials can I put in my compost bin?
There is a large range of dry carbon materials you can source for your compost system. These include:
- Shredded office paper
- Newspapers that use soy-based ink
- Aged sawdust
- Brown cardboard.
- Never use glossy magazines or brochures, the chemical inks can compromise the compost’s health
Top tip: Have a weatherproof bin storing dry carbon materials directly next to your compost bin. This will make it nice and easy for you to add a carbon layer each time you add your food scraps.
Things you should never put in your compost
There are a few things that should not go into your small compost bin, tumbler or bokashi bin. Avoid these things:
- Weedy plants, twitch grass (and other runner grasses), ivy, thistles and gorse to name a few. (These plants need a large hot compost pile to kill them or, send them to the council’s large-scale composting facility.
- Diseased plants.
Understanding the compost ‘carbon to nitrogen’ ratio
OK, so now you understand the difference between nitrogen (‘green’) ingredients and carbon (‘brown’) ingredients.
So – most compost systems (except worm farms) require a carbon to nitrogen ratio of about 25:1 or 30:1. This means it’s good to get to know how carbon-y or nitrogen-y different compostable materials are, then you’ll know how much of each thing to throw in your compost bin to create a thriving environment.
Below is a table that shows things like fish guts and chicken poo are really high in nitrogen, while things like cardboard and sawdust are really high in carbon.
|Inputs||Carbon to Nitrogen Ratio|
|Fish guts||10:1||Really high in nitrogen|
|Mixed, fresh food scraps||15:1|
|Fresh grass clippings||15:1|
|Fresh cow poo||17:1|
|Fresh horse poo||27:1|
|Draw Sawdust||200:1||Really high in carbon|
Other good stuff that your compost loves
- Yarrow, comfrey, stinging nettle, plantain and dandelion are compost activators, which are nutrient-dense ingredients that you can add to your compost system in modest amounts.
- You can also add small amounts of “rock dust” to remineralise your soil. Rock dust is available from nurseries and some quarries, look for a quality product that’s tailored for food production. (source or re-write)
Choosing the best compost bin for your context
You’ll need somewhere specific to build your compost pile and store your food waste and other organic materials while they’re composting. So let’s look at three types of compost bins that are great for different reasons in different contexts – the black bin, the tumbler and the Bokashi bin.
Option 1: Black compost bin
Black bins that sit directly atop the soil are popular in backyards of all sizes – because they are super easy to use.
They are a cold compost (mesophilic) system, because they are smaller than one cubic metre. (Bigger compost piles get super hot, but that’s a whole other story we’ll cover another day.)
How to use a black compost bin
- In a small compost bin, you layering carbon and nitrogen materials. To start, put down a 15cm layer of carbon and then add a 7cm layer of nitrogen (mixed food scraps cut up to the size of a 20-cent coin) and repeat until the bin is full.
- Add water between each layer as you go.
- Once you get going, every time you put a bucket of food scraps in, put two buckets of carbon materials in too.
- Never add weedy or diseased plants to a cold compost system.
Two bins for the win
Because you’re adding materials gradually, things will compost at different rates, meaning you’ll have mature compost at the bottom while you still have fresh food scraps at the very top. For this reason, you need to have at least two compost bins so you can rotate between them, letting one rest (and mature) while you use the other.
Spin your compost, round and round
Turn your compost bin using a ‘compost screw’ or a garden folk – this accelerates the composting process. Start turning the bin’s contents once it’s filled and has rested for a few weeks, then you can give it a turn about once a week until it’s full composted and ready to use.
A tip for avoid rats and other vermin
If rodents are coming into your compost bin from under the earth, add a layer of ‘vermin mesh’ directly to the bottom to stop them from being able to dig under. You can buy vermin mesh from most hardware stores.
- Place the mesh on the ground and mark out a circle approximately 10cm bigger than the bin’s base.
- Fold this extra bit of mesh over the existing lip on the compost bin – this is enough to hold it in place.
- You’re now ready to place your bin in your chosen spot.
Alternatively, keep your compost bin on a free-draining, hard surface such as some bricks to reduce the likelihood of rodents getting in. Make sure any liquid drains to some nearby earth.
Option 2: The compost tumbler
Compost tumblers are a great option for people with limited space, rodent issues or those looking for an ergonomic option that limits bending and lifting.
To make sure they work well, here are some basic tips to follow.
- Before adding food scraps, make sure you take an extra 10 seconds and chop everything up to the size of a 20-cent coin. This will help it all break down quickly.
- Every time you put in food scraps, add some fine carbon material as well such as shredded paper or straw. Just like the small and large compost piles, you’re aiming for a carbon to nitrogen ratio of 25-30:1.
- To aid in good drainage and increased airflow, drill hundreds of 10mm holes into your tumbler with a power drill.
- Place them in full sun over winter. During summer place them where they get morning sun only, so they don’t dry out too much.
- Only fill your tumbler a half to three-quarters full, otherwise they get too heavy to turn.
Option 3: The Bokashi bin
Bokashi is Japanese for ‘fermented organic matter’ – these small bins are designed to be used in your kitchen, literally atop your bench, if you want.
The system includes a purpose-made bucket with a lid and drainage tap. They vary in size and can be up to 20 litres in volume. The kit also comes with a dry bran mixture (made from rice husks and wheat) that has been inoculated with effective microorganisms.
The microorganisms ferment the food scraps, eliminating any bad smells, and are a biologically active living material that can then be transferred to your garden to finish composting in the ground, where it improves soil health.
How to use a Bokashi bin
- Add your food scraps into the bin as you make them.
- All food scraps can go into the bin including dairy, meat (without large bones) citrus and cooked food.
- Make sure you take the time to chop the scraps into the size of a 20-cent coin to accelerate the composting process.
- Sprinkle in the inoculated bran mixture directly after adding food scraps and press the scraps down to remove air pockets.
- If it starts smelling gross, add more bran.
- Continue to add food scraps until your bucket is nearly full, and then let it sit for around ten days to ferment.
- Every few days you will need to drain off any liquid, dilute this with water and add to your garden.
- Next, bury the contents in soil so they’re completely covered. From here the composting process will continue with the aid of the effective microorganisms in the bran material. If you don’t have your own garden, find a friendly neighbour or community garden to take your biologically activated food scraps to.
Troubleshooting: What’s wrong with my compost?
Help! My compost is…
Breeding maggots: Remove any meat or excess food. Add a sprinkle of lime and cover with a layer of carbon such as a hessian or wool blanket.
Really smelly: It’s too wet and likely to be anaerobic (not enough air). Mix in more carbon materials, turn and add a touch of lime which will help bring it back into balance. Alternatively, you may have overloaded your compost system with too much food waste. Remove some and start a second compost system to cater for the amount of food waste you’re producing.
Infested with ants: Your compost system is probably too dry or has exposed food. Add water if dry and cover any exposed food scraps on top of the system with carbon and hessian/felt. You can also turn the compost if in a compost bin.
Taking ages to break down: You may need some more nitrogen and/or water to get the party started. Add more nitrogen (food scraps, some manures, green lawn clippings) and water. Empty your compost bin into a pile and rebuild it to get a good balance of carbon and nitrogen throughout.
Swamped with small black “vinegar” flies: Some Drosophila flies (also known as vinegar flies) aren’t a bad thing – however, a lot can become annoying. Make sure you have no exposed food scraps by covering the top of the compost with a layer of carbon such as a piece of hessian or wool blanket. You can also place a small jar of vinegar in the top corner of the bin, this will attract and drown excess flies.
Home to rats and mice: Reduce the amount of food you’re putting into the system (especially bread and meat). If you have a small compost bin, add vermin mesh on the bottom of the compost bin to prevent rodents from digging under. You can also dig your bin 20cm into the earth or place it on a free-draining hard surface (bricks or concrete). Make sure any liquid leaving the system is draining into the nearby earth. If rodents are really bad, consider building a worm farm made from a recycled bath as rodents can’t chew through baths with hardwood timber lids.
My compost tumbler has become gross and stinky: It’s likely to not be draining well due to its limited air and drainage holes. With a power drill, drill hundreds of holes around its full circumference, 10mm in size. This will drastically increase the airflow through the system and allow excess moisture to drain freely.
My compost tumbler is too heavy to turn: Only fill your tumbler up half to three-quarters of its capacity to ensure you can still turn it easily.
Other excellent ways to reduce food waste & save money
Once you become a composter, you’re essentially a food waste hero – diverting all that fertiliser gold from landfill back into the soil, to make more food. Go, you!
It’s a great idea to also take a couple of steps back and think about how you can create less food waste in the first place – this will also save you money too.
Get started with these 7 tips:
- Plan ahead before going shopping, check the food you already have and make a list of meals for the few days or week that can incorporate those things.
- Write a shopping list, and stick to it, this will help you buy only what you need. Impulse buying creates tons of food waste.
- Think versatility: Choose fresh ingredients that are easy to use for more than one meal.
- Eat seasonally: Buy fruit and vegetables that are in season, they stay fresher for longer, are usually more affordable and have fewer food miles.
- Cook cleverly: cook meals with portion size in mind.
- Love leftovers: choose recipes that are easy to reheat the next day for lunch. Leftovers are your helpful friend. They’re quick and tasty meal options. If you’re not going to eat them within a few days, store them in your freezer.
- Savvy storing: Make sure your fridge is set between 3 -4 degrees and your freezer at -18 degrees and has all seals working. Put leftovers in sealed containers and cover your vegetables with a clean tea towel to absorb excess moisture. Store potatoes in a cool dark place with no exposure to sunlight (which causes them to sprout). Store your dry foods (flour, pulses, pasta) in airtight containers in your pantry. Keep bread in a bread box (not the fridge), if it starts to go stale, store it in the freezer.
Alrighty, lovely – time to go forth and start composting! Any questions, please let us know in the comments below, we’re here to help.
And a huge thanks to our dear friend Hannah Moloney from Good Life Permaculture who wrote this most excellent ‘Home Composting in Hobart’ Guide, which we’ve used as a reference point for this article.
More compost resources…
- Hannah Moloney’s ‘Home Composting in Hobart’ downloadable guide
- The Beginner’s Guide to Worm Farms – watch the Milkwood video and expand your composting repertoire.
- How To Build Healthy Soil for Your Best-Ever Veggies – a free Milkwood workshop video on ways to use your compost.
- Read about How Brydie Became a Compost Geek – a Milkwood article with some ace composting tips.
- Learn how to hot compost with Good Life Permaculture – a great solution for a bigger garden.
- Learn 5 ways to compost in-situ with Morag Gamble – a masterclass from the Permaculture Education Institute.
- Want to compost your dog or cat poo too? – a fab video tutorial by Green Hub.
- And you can browse through all our articles on compost and nutrient cycling.
About the author: Nat Mendham is a front-yard gardener, visible mender, daily walker and Digital Content Producer here at Milkwood. When she isn’t writing and creating digital things about climate action for Milkwood and beyond, she’s putting theory into action in rural lutruwita/Tasmania.
We acknowledge that permaculture owes the roots of some of its theory and practice to traditional and Indigenous knowledges, from all over the world. We all stand on the shoulders of many ancestors – as we learn, and re-learn, these skills and concepts. We pay our deepest respects and give our heartfelt thanks to these knowledge-keepers, both past and present.