Composting 101: How and Why to Compost at Home
What is compost? What's so good about it? What is it used for? Why is it so important to do? How can I make my own? In this post I aim to answer these questions and demystify some common composting myths.
Compost is the end result of breakdown of organic (once-living) matter into a reusable form. It is recycled natural matter - plants, food scraps, manure, etc – made in a practical, usable and controlled way. Composting was around even in ancient Roman times and is recognised in agriculture, permaculture, horticulture and the likes as one of the best ways to improve the health of degraded soil. Good soil is full of living organisms, nutrients, water, carbon, and many other things. It can also absorb and store carbon. When we grow crops or graze animals and don't replace what we remove (during harvest, topsoil aggitation or animals feeding) soil health deteriorates. By creating compost, we can easily and cheaply revitalise soil to maintain great crops, on both a small and wider scale.
Finished brown gold
Food waste is a problem in Australia of EPIC proportions - we throw out one in five grocery bags of food! That equates to roughly $3500 dollars per year for the average Aussie family. One third of our rubbish bins, household and industrial, are full of food waste. Can you think back over the last week to what food you might have thrown away, edible or otherwise? That leftover curry that was forgotten in the back of the fridge, that apple that got squashed and mouldy in the fruit bowl, that tub of yoghurt past its use-by date... OK, so you’ve wasted a bit of money, but it all just breaks down nicely in landfill anyway, right? Wrong! When organic matter is trapped underground or in plastic with no air exposure (i.e. anaerobic, oxygen-devoid conditions) it takes a really long time to break down (I’m talking years) and produces methane in the process. Methane is climate change's arch nemesis. It's about 23 times more potent than carbon dioxide, contributing heavily to trapping hot air in our atmosphere (see here for the Australian evidence from RMIT University). Yes, this is the same gas that gets talked about most when climate impacts of animal agriculture come up (cow burps, mostly!). So, unless we’re quietly facilitating a lovely aerated biodiverse environment for your food scraps, we’re giving the old middle-finger to Mother Nature.
Of course, the first thing we can do to combat this massive issue is to reduce your food waste – follow my blog and socials for more tips on this, or any other good zero waste advocate. Once you've already made a great effort to do this, you'll notice you still have some scraps that are always left over. Your first thought now should be compost! If you're thinking things like, "I'm not a gardener, I don't know anything about composting", or "I'm in a small unit, I've got nowhere to put a compost heap", or "Do I just buy one of those big black bin things and fill it up?" then pause, relax, and read on..
There are so many ways you can make compost, and each gardening guru and waste warrior will have their own method they like to use. There isn't really one perfect way to compost, which is great because it makes it harder to get it wrong! I'll aim to cover the most important stuff to get you started, and the rest is up to you and your bin full of bacteria. At the bottom of the post are some resources to help you once you're up and going.
Firstly, a note for those living in a small space without a yard (scroll down if this isn't you). There are a few ways you can divert your food scraps from landfill without having to create a big pile. If you do grow plants (e.g. on a balcony garden) you can opt for a Bokashi system which is tiny, faster and smell-free for indoors. Read my past blog post on this for more info. If you don't grow anything, you can still collect your scraps in a separate bin and either contribute to a friend's compost or worm farm, or donate them to a local community garden or school compost, or jump straight on the ShareWaste app – this app has been a lifesaver for many of my friends! Just list yourself as either a food scrap donator or acceptor, and find someone to accept/donate scraps in your suburb – voila. Some local councils have food scrap collections just like normal rubbish collections, where your small kitchen bin (provided by them) is emptied into a big industrial pile and hot composted by them. Down here on the surf coast we do not yet have this up and running. A worm farm is also very compact and, if you live alone, is a great way to use food scraps. They require small weekly or fortnightly donations and, in return, you get the best soil conditioner known to man - worm poo!
Layering my cold compost pile
Compost basics to get it right
We've all heard about carbon and nitrogen - in compost, they are your core ingredients. Carbon is highest in dry, brown material, such as dried leaf litter, cardboard, newspaper, unbleached packaging/egg cartons, straw, old woody plants, twigs/old plant prunings, woodchips and wood ash. Nitrogen is highest in fresh or green material, such as kitchen scraps (mould is fine), cut grass, young weeds, animal manure, comfrey and nettles, seaweed, soft prunings, and hair/fur.
Your receptacle can be anything from a plain plastic enclosed bin, to a large open timber frame. You need to keep the pile together at the very least, and enclosing it can protect it from the elements and vermin. For a hot compost, you need at least 1m cubed (ideally more) for the heap to reach 60 degrees celcius (at which most seeds and pathogens are killed). Hot compost also breaks down much more quickly and kills pathogens when made correctly, but is not always a practical option. Cold compost takes longer (months as opposed to weeks), is very simple, and is suited to most households with a garden bed or yard.
It’s important to layer your compost when you first make it (take it from someone who learned the hard way) with a rough ratio of 25:1 carbon to nitrogen (note: some brown materials are higher in carbon than others, and vice versa). Start with something like cardboard or newspaper to line the bottom and keep pests out, then add your nitrogenous or green layer, followed by brown, then green, etc. Continue this until your bin is full (or you have run out of ingredients, in which case continue to build over time with this layering system). The simplest key to this is: minimum one bucket of brown for every bucket of green (scraps). A variety of materials generally makes a better compost, as you'll have a wider array of bacteria and nutrients available at the end. Ensure throughout that you keep brown layers light and fluffy, i.e. don't compact them down. Air is vital to the process. Moisture is also essential part so, if your mix looks dry or dusty, give it a sprinkle or add more rich scraps to keep it damp. Additional animal manure and lime can be added if you want to speed up decomposition, while turning (or fluffing) your heaps helps too. Don’t stress too much about turning your compost, though everyone will tell you their opinion on this – it can help, but I promise it’s optional. It is, however, a good opportunity to check your heap and see what it's doing, feel the temperature, and smell it. A finished compost is a rich, dark brown soil that should smell sweet - almost edible! Food scraps should be basically impossible to see. When you use it, any big bits left are best sieved out and put back in to continue rotting in your next pile (avocado pips, corn cobs, sticks).
Use your finished compost wisely - more is not always best, and it is very valuable! It is best spread on the veggie patch, in pots or at the base of fruit trees in spring and autumn, watered in, and mulched over to keep it moist. Digging it into the top layer is optional, but be mindful not to ‘turn’ the soil too much as its layers are home to very specific bugs whose populations can be damaged with too much turning.
What NOT to compost in your backyard heap*:
- Cat, dog or human faeces
- meat, bones, dairy and fatty food (optional, can attract animals)
- most diseased plants
- chemically-treated wood products
- charcoal ash
- noxious weeds, especially with seeds
*many of these things can technically be composted, but they require specific environmental controls that are not available to the average household.
**I personally choose to avoid putting too many salty foods in my compost too, like lots of leftovers or salt spills, as high salt levels are detrimental to soil in many ways.
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Gardening Australia Compost Fact Sheets - Costa Georgiadis
YouTube- War On Waste (ABC TV) Food Waste clip