Here is a summary of the terrific talk MJ gave on one of the last working bees regarding our beautiful compost:

Compost improving our soil

At Mort Bay Community Garden we use compost as one of the key ingredients to top up our beds and to enrich our soil with organic matter.

We recently improved our compost area, which is situated in a cool and shadily spot at the big retaining wall along Short Street. It’s now paved and it’s easy to access the bins in which we collect compost-able material, newspaper sawdust and wood-chips.

We love our members to bring their compost-ables

Mort Bay Community Garden invites its members to contribute their kitchen/green waste to our composting system. We have a series of bins to which waste can be added.

There are waste products that definitely SHOULD NOT be added and those that are welcome:

  • we encourage contributions of kitchen waste of fruit and veg, coffee grounds, tea leaves, smashed egg shells etc.
  • leaves and cuttings of the plants in the garden beds of our garden are also very welcome. Please cut them into smaller bits, so they can break down more quickly.
  • we DO NOT want meat, wheat products, pineapple heads, coconut shell, plastics, nappies, dog or cat waste, thick cardboard, plastic bags or bio-degradable (plastic bags take too long to break down).

Please note the signage on the bins that also explains what is welcome and what is not. If waste is added to the bins, please also top up with some shredded newspaper or a bucket of sawdust, that can be found in the wheelie bins next to the compost containers.

Hot compost

To change all the collected scraps into compost, it has to break down naturally. This process usually takes half a year to a year and involves the joined effort of chemical processes and lots of fungi, microorganisms, worms and insects.

To facilitate this process we use a hot compost system with the benefit of an aerobic system, high temperatures (55 to 65 degrees C) and water, that can achieve this result in 4-6 weeks, depending on what’s in the compost and on the weather conditions. The hot compost pile is created in the three wire bins at the north end of the compost area.

To make a hot compost work you need

  • a ratio of 25-35 : 1  carbon to nitrogen material. Since waste is made out of both, we aim for a ratio of 1/3 greens to 2/3 browns
  • the pile has to be high
  • the pile has to be left in peace for five days
  • from the sixth day on the pile has to be stirred frequently to aerate it
  • the pile has to be stirred from the outside to the inside and vice versa

The carbon materials are often brown and dry like dried leaves, fibrous stems, straw, sawdust, cardboard, ribboned newspaper

The nitrogen materials are often green and moist like clippings, green waste from the community garden, fruit and veg waste

Setting up a pile each month

To set up the pile we layer the brown carbon components with the green nitrogen components in many layers  and then soak the pile with plenty of water. It is then covered with black plastic and nothing else gets added.  The water, the air along with the heat developed by the chemical reactions in the pile help breakdown all the components in the bin.  After approx 5 days the contents of the wire bin needs to be turned inside out to release the heat and aerate the pile. We continue with this turning process every few days for about a month to 6 weeks. When the heat builds up the worms head down to the bottom of the pile and they return when it cools down helping with the breakdown process.

The hot compost quantity will decrease by 50% leaving a rich earthy consistency.  We sift our compost twice to remove items that take longer to break down, for example: avocado stones and woody stalks.