Our Composting

System

Why All The Composting Fuss?

Composting is nature’s recycling system, a simple, powerful way to turn garden waste into living soil. At Grow Forrest Hill, we follow a four-bin process that mirrors the natural life cycle of decomposition, from hot microbial action to cool, worm-filled soil.

Each bin represents a different phase in this journey, and together they tell the story of transformation happening right here in our garden. Read on to learn more about what’s happening at each stage of the composting journey

Oh, and feel free to come join us in person. We host our ‘composting club’ on the first Sunday of each month during our working bee. 2 pm - 4pm.

Bin 1 – Combining

On the first Sunday of each month we host Compost Club where we build a hot compost by layering nitrogen rich greens (garden waste, kitchen scraps, grass clippings) and carbon rich browns (wood mulch, dead leaves, shredded cardboard). This begins the first phase.

MESOPHILIC PHASE

If the compost pile is built correctly, with a good balance of nitrogen, carbon, water and air, the compost bacteria will show up. They will quickly get to work and start breaking down the pile. As they combine carbon with oxygen, they produce carbon dioxide and energy. Some of this energy is used by the microorganisms themselves, to grow and reproduce. The rest is given off as heat, which increases the temperature of the pile. The mesophilic bacteria thrive in these rising temperatures, up to about 45C. This is the first phase of composting, which will last a few days if conditions are good. Over the next couple of weeks the next phase, the thermophilic phase kicks in.

Microorganisms at this stage include bacteria and fungi.

Bin 2 - Cooking

After a month in bin one the contents is flipped into bin 2, this re-oxygenates the pile and boosts the compost eating microbes into action resulting in a rapid rise in temperatures.

THERMOPHILIC PHASE continues

As the pile heats up further, a different set of bacteria moves in. Thermophilic bacteria thrive in temps from 45C – 70C. At temperatures above 45º, any type of biological contaminant is destroyed, which contributes to the sanitisation of the mixture. This heating stage takes place pretty quickly, as the heat-loving bacteria multiply rapidly, devouring all of the readily available nutrients. During the thermophilic phase, the mixture must be moved and aerated with the main purpose of providing oxygen to the microorganisms in it so that they can continue decomposing it.

Microorganisms at this stage include mites, nematodes and Protozoa.

Bin 3 - Cooling

In the third month, the contents is flipped from bin 2 into bin three, and the compost cools allowing the worms to move back into the pile.

COOLING PHASE

After the thermophiles have done their work, the pile still has some pretty coarse material in it and the temperature will start dropping. Those mesophiles that were there in the beginning will return, because they are happy in the mid-range temps.

As well as the return of bacteria and fungi, organisms at this stage include ants, beetles worms and other invertebrates.

Bin 4- Curing

In the 4th month the compost is flipped for the final time and our volunteers run it through a screen to get a finer grade of compost. This maturing stage results in a top notch product.

CURING PHASE

This is the longest and most important phase, and it’s worth the wait. Maturing your compost ensures that it is completely free of pathogens, breaks down tough plant fibres and makes a wide range of nutrients available to plant roots. While it rests in bin 4, we get busy starting the whole process over again (refer back to bin 1).

A wide range of invertebrates join the ecosystem of the compost at this stage, including centipedes, slugs and slaters.

FAQs

What can you compost?

Many things can be composted. You can really compost almost anything that ever lived.

  • All food waste. (Veggies, fruit, Bread, Pasta etc)

  • Meat and fish are easily composted too. (Some compost makers avoid meats because they are concerned about pests. Our compost bins are rodent proof so this is not an issue.)

  • Compostable packaging and paper towels.

What can you not compost?

It is important to know what cannot be composted so that your rubbish stays separate from your compost and goes into the right place. Things that you should not attempt to compost include:

  • Plastic

  • Wood, timber, and large sticks

  • Metals, rocks, etc.

  • Cardboard. (Technically we can, but this is better put in your home recycling)

Does composting attract pests?

The CarbonCycle Compost bins we have are equipped with pest-proofing on all surfaces, including the base. So in short, nope, no pests.

Does the compost smell bad?

There is no reason why a well-tended compost pile should smell. If it does, then it probably has too little carbon – easily solved… we will add more. It is all about getting the balance right, and that is what we work on each week at our working bees.

How long does it take before you will have usable compost?

This depends on many factors including the size and nature of the mixture, the weather, how often we turn the compost, etc. In our experience, usable compost can be expected in moderate conditions within a few months, if turned at least three times.

How can I get in on some of this compost you are making?

At this stage we have a very hungry garden, so we anticipate using all the compost we produce. If it turns out we have some to spare, we will sell bags as fundraisers for the garden. Watch this space.