Botanic Gardens Trust, Sydney, Australia

Composting

What is composting?

Composting is nature’s own recycling program. In time, organisms will break down the ingredients listed below into rich, dark crumbly compost - nature’s own nutrient-rich fertiliser.

How does composting work and how long does it take?

Natural composting, or decomposition, occurs all the time in nature. Home composting generally takes two months or more. The more you turn and mix the contents - adding air in the process - the more rapid the composting action will be.

The right conditions include

  • the right ratio of nitrogen to carbon - equal amounts of ‘greens’ (kitchen scraps) for nitrogen and ‘browns’ (fallen leaves and woody material) for carbon
  • the right amount of water (feels like a damp sponge)
  • good drainage (to remove excess moisture)
  • enough oxygen (turned often)

What can you compost at home?

  • Vegetable and fruit scraps
  • Fallen leaves
  • Grass clippings
  • Finely chipped branches
  • Used vegetable cooking oil
  • Tea leaves, tea bags
  • Coffee grounds
  • Vacuum cleaner dust
  • Egg shells
  • Sheets of newspaper
  • Paper bags
  • Shredded paper

What can’t you compost?

  • Metal, plastic, glass
  • Meat and dairy products (attract rodents)
  • Large branches
  • Bones
  • Plant bulbs (need specialised treatment)
  • Droppings of meat-eating animals (e.g. dogs)

Grubs in your compost?

Sometimes in compost bins there are many segmented brown grubs. These are the larvae of the beneficial Soldier Fly. They are not pests, nor will they cause health problems.

Mulches

  • Mulches can prevent up to 73% evaporation loss and they are one of the cheapest and easiest ways to make the most of water in the garden.
  • The best mulch is a well-rotted compost which will also improve the soil structure and stimulate the biological life of the soil. Place the mulch away from the trunk to prevent collar rot.
  • Do not apply mulch more than 75-100 mm in thickness or water may not easily penetrate into the soil.

Sylvester the Digester

At the Royal Botanic Garden Sydney we have one of only a few VCUs - Vertical Composting Units - in Australia. Our VCU, nick-named ‘Sylvester the Digester’, will help us lead the way in responsible recycling to help save our environment. Sylvester is an insulated, weather-sealed unit that processes organic waste and turns it into a nutrient-rich compost. We are turning our green ‘waste’ material into a high quality mulch and soil conditioner.

Sylvester is filled with fresh waste, water is added, then the waste is transferred to the top of the unit to descend through a temperature gradient from 85ºC to 45ºC. The high temperatures ensure elimination of pathogens and weed seeds. Sylvester is at work 24 hours per day, seven days a week. The time required to make the final compost product is around two to four weeks.

Sylvester was bought with assistance from the New South Wales Government through the Waste Fund. Click her for further information on this sustainable organic waste solution.

What benefits does Sylvester provide?

  • We are helping the environment by recycling our green waste.
  • We no longer have to send our green waste for composting offsite.
  • The finished product is high in quality and free of pathogens and weed seeds.
  • We are saving energy - Sylvester only uses a small amount of electricity per tonne of waste.
  • Sylvester is a sealed unit, so he doesn’t smell or have problems with insects or vermin.
  • Sylvester has minimal moving parts so maintenance and operating costs are low.

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Vertical Composting Unit

compost bin

What to put in the compost