Green cone user guide

1. Overview

Sales of the green cone biodigester have been put on hold until further notice because of the restrictions introduced by the Victorian Government.

A green cone is a completely natural system that decomposes your waste to its natural components of water and CO2. Over 90% of waste will be absorbed as water by the soil. The process work because of: 

Sunlight

Provides an energy source for the cone.

Double walled solar cone

Creates a heat trap of circulating air to encourage bacteria growth and also insulate in winter.

Digestion chamber

Supports appropriate conditions to create aerobic digestion and also reduces methane production.

Water

Evaporates from food waste for aerobic composting.

Soil

Filters out odour and prevents access by flies.

Rich soil conditioner

Seeps into surrounding ground.

Natural micro-organisms and worms

Migrate freely in and out of basket and break down the waste.

Diagram of a Green Cone digester indicating how solar energy is used to digest waste then transition into the soil surrounding the cone. The Green Cone is 70cm tall above ground and 60cm wide with a basket 42cm tall hidden below ground.

2. Standard installation

Before starting to install your cone, make sure assembly is complete(PDF, 218KB).

Step 1

Choose a sunny spot in your garden: the sunnier the better.

Make sure there are no underground pipes, cables or tree roots.

Step 2

Dig a hole 80cm wide by 60cm deep in good draining soil. If you have heavy clay or chalk,dig the hole 90cm wide and 70cm deep.

If you hit solid clay when digging the hole, consider a larger hole or raised bed installation to use your cone.

Check if you have good draining soil after you have dug the hole by pouring a bucket of water in to it. If the water disappears within 10-15 minutes, your drainage is good. If not, dig the hole deeper and add stones.

Step 3

Mix some soil from the hole (do not use clay or chalk) with either:

  • stones
  • gravel
  • compost.

Use this mix at the bottom of the hole, and as back fill once your cone is in place.

Step 4

Place your cone in the hole on top of the mix. Make sure the top of the basket and bottom lip of the cone are below ground level.

Use the rest of your mix as back fill, and make sure the bottom lip of the cone is covered.

The soil level will drop after installation and heavy rain. Check periodically that the bottom lip of the green cone is covered.

3. Installation in clay and chalky soils

Clay and chalk can cause problems with drainage. It is important that the water produced by the cone can drain into surrounding soil.

Your cone will not work properly if:

  • the basket is standing in water
  • produces smells.

Option 1: Standard installation with larger hole

If you have heavy clay or chalk you can dig the hole 90cm wide and 70cm deep.

With persistent rain the bottom of the larger hole could still fill with water.

Option 2: Raised bed installation

To make a feature of your cone and make sure it works correctly you can install it in a raised bed.

Step 1

Dig a hole ~30cm deep and totally fill it with small stones.

Step 2

Stand the cone on top of the stone at ground level.

Step 3

Build a rockery around the basket, leaving about 15cm gap around the cone to back fill with soil or wooden slats.

Example of an alternative way to have a Green Cone installed within a raised bed
Example of a Green Cone installed within a raised bed

4. Using your green cone

Your cone will breakdown a wide variety of food waste including:

  • Fish
  • Meat
  • Poultry
  • Bones
  • Dairy produce
  • Crushed egg shells
  • Bread
  • Pasta
  • Tea bags
  • Coffee grinds
  • Soup
  • Curry
  • Cooked food scraps
  • Fruit including peelings
  • Vegetables including peelings

The cone is not a composter, and will not handle garden waste.

A hard working green cone

In a healthy working cone, food waste will be covered in a blue/grey fur: this is the bacteria doing it's work. You should see it start to build up over the first 10-14 days.

If the level of bacteria starts to disappear you can add some accelerator power. Do not use any chemical activater in your cone as it could kill the bacteria.

A cone that is not positioned in a full day's sun, or when there are long periods of cold weather, benefits from occasional application of accelerator powder to aid the digestion process.

During summer

The cone is designed to handle the equivalent of a 4.5 litre container every 1-2 days during summer.

During winter

The cone is designed to handle the equivalent o a 4.5 litre container every 2-3 days during winter.

5. Maintenance

Your cone needs little maintenance, though it is a good idea to follow these tips:

  • make sure the top of the basket and the bottom lip of the outer green cone are below ground level and always fully covered with soil;
  • keep the area clean and free from food waste to avoid attracting pets or vermin by cleaning the lid and cone exterior; and
  • avoid spilling food waste on the ground near the cone.

Residue build-up

Little residue is produced in a well-operating cone. If residue does build up to ground level and does not decrease:

  • remove the upper-cones to access the basket; and
  • mix the residue into any suitable area of your garden as soil conditioner or add to a composter.

For a family of 4 with average consumption, the in-ground basket should only need emptying every 2-3 years.

Flies

The cone is a sealed unit and when properly installed does not smell and will not attract flies.

Though fruit or house fly eggs may be in fruit skins, especially oranges and bananas, they can hatch in the cone and produce maggots.

If flies become a nuisance, fly spray works quickly and will not kill the bacteria needed to digest the waste.

Wet and slimy food waste

If waste in your one is looking wet and slimy, this is normally because of poor drainage. Waste that has broken down and turned into water cannot seep in to the surrounding soil, or the water has come from heavy rain.

Full basket of food waste

If you put more than the recommended maximum amount of waste in, it will not have sufficient time to break down.