How good is compost? You throw a bunch of organic waste into a pile, it heats up, and these things called microbes come along to transform your rubbish into a precious garden commodity! The earth has been doing this forever, locked in an endless cycle of growth, death, decay, compost and fertilisation. Nutrients are reused again and again. In this way, composting is the ultimate form of recycling, and there is no greater satisfaction than seeing those tangible results in your own garden.
Fully matured compost is pH neutral and can be used to propagate seeds, but when added to your patch holistically it’s like a shot in the vein. It contains a broad spectrum of nutrients and all the essential trace elements so that it not only boosts a plant’s growth, but also the overall activity of life in your soil. Compost is the number one candidate for making soil into something living and correcting any imbalances. It wins Soil Additive of the Year hands down every year.
About half of our household waste is organic – things like food scraps, coffee grounds, paper and cardboard. It all adds up. When this is mixed with waste that’s not organic in a landfill, nothing decomposes properly and the end results are harmful greenhouse gases. Think of organic waste as a powerful weapon that can be used for either good or evil. The very same material can either damage the environment or improve it. Therefore, composting is just as much about avoiding the landfill as it is about creating an organic fertiliser; the time, space and appetite you have for those two outcomes will determine how you decide to compost.
Types of waste
Making compost is like baking bread. It takes the right balance of flour and water to make the perfect dough just like it makes the perfect balance of green and brown wastes to make the perfect compost.
The ideal ratio, 2-parts green waste to 1-part brown waste, enables composting to occur fast and efficiently. When out of balance, compost turns into a stinking den of sin (too much green) or a dusty old saloon (too much brown).
Green waste is ‘wet’ waste, comprised of nitrogen-rich plant material such as kitchen scraps, but also fresh garden trimmings. It’s the main source of food for composting microbes.
Brown waste is ‘dry’ waste, including carbon-rich plant material such as straw, wood chips, dry leaves, paper, cardboard and sawdust. These lightweight, dry materials help to aerate the compost bin, providing oxygen and carbon for the microbe diet.
Animal waste (meat, fish and dairy) should not be composted in this fashion. It not only attracts pests, such as rats, but produces anaerobic bacteria which work against oxygenated (aerobic) composting, causing odour and changing acidity. Rancid meat and dairy can also foster harmful pathogens like our old friend E. coli. There is a way, however, to ‘compost’ such scraps in a bokashi bin. It is a form of fermentation that helps breaks down the wastes, converting it into a nutrient rich plant tonic.
Efficient composting systems require a minimum of 1m3 of waste to generate high internal temperatures – up to 50–60oC – to then produce pure compost. Heat breaks down pathogens and also fosters an ideal environment for helpful microbes, which further aid in breaking down waste. These microbes require oxygen to work best and all parts of the pile need to be exposed to the internal high temperature, so the entire batch needs to be mixed and turned over from time to time.
It requires a lot of waste and work to create the perfect compost, meaning that all household systems are imperfect. For this reason not everything will be broken down properly and you will find seeds sprouting out of them; hopefully just bonus tomatoes and pumpkins! That doesn't mean, however, that you still can't create an incredible gardening commodity and dramatically reduce your landfill in the process.
Types of household composting systems
As with everything in life, we have to strike a balance between best practice and what is practical in our situation. We may not be able to make perfect compost, but we can get close. Everyone has the potential to compost a little and to reduce landfill. In our households, we generate bits of waste every day and we can compost them in a number of ways.
Trench composting This is the no frills, no fuss style of composting our grandparents used to do. Dig a deep trench in the garden bed – to 30 cm (12 in) in depth – fill with organic waste and cover with soil. So simple and so good. Trench composting relies on worms and microbes to come and breakdown the waste in situ. As the compost forms nutrients are immediately available to plants. No double-handling! If you're interested in a more user friendly/faster version of trench composting, try building a worm plunger.
Open above ground bin This is a big plastic bin that sits over the ground with an open bottom and a lid on top. These systems have a great capacity – usually about 220 litres – and seemingly never fill because they are in a constant state of compression and decomposition at the base. For better or worse, pests can also help to reduce the volume and have been known to tunnel great distances to get inside and feed. However some simple wire chicken mesh laid underneath the base will prevent rodent access. The great limitation of this type of bin is that it is hard to access the compost, which forms on the bottom first, so the best practice is to have two bins operating simultaneously. As one fills up completely, the second can become the new working bin while that one has the chance to fully mature.
Closed above ground bin Like the open above-ground system, but closed on the bottom and with a low access spot to collect the compost to help overcome the limitation of the system above. It also has air vents that are meant to encourage aerobic activity. While this type of bin has advantages in theory, because it is closed on the bottom and not open to the earth it locks out our composting friends such as insects and worms.
Enclosed tumbling bin This self-contained system is a rotating cylindrical bin that is suspended in the air and can be spun. The rotating function is meant to help give all the waste the chance to heat up and turn into compost, but since the units are generally so small - and people enjoy spinning things so much - it never quite heats up enough.
Getting the balance right
In general, we tend to have much more green waste than brown. Food scraps go into the bin every day and the result is that our compost can get a bit saucy, sloppy and stinky. When there isn’t enough brown waste to balance the mix, too much moisture and nitrogen can create an anaerobic environment. Food starts to rot and ferment, rather than decompose - which is exactly what happens at a rubbish tip but to a much greater scale. A good composting environment needs about two parts green waste to one part brown. To alleviate this problem have a bag of mulch handy and correct the balance by adding a small scoop every time food scraps are emptied into the compost bin. This gets you into a good routine and in time you can ditch the mulch and begin incorporating legitimate brown wastes.
If you find your compost bin becoming a stinky mess that seems unredeemable, you can make a compost aerator as a simple solution for alleviating the stench.