Help, my bin's starting to smell ...

If your hungry bin is starting to smell, or the food is rotting before the worms can eat it, add a fine layer of fibrous brown material each time you feed the worms to help balance the bin. You can also sprinkle a fine layer of soil or potting mix into the bin to help balance it. A diet of food scraps can be too rich for the worms unless the scraps already contain plenty of fibre (lots of vegetable stalks for example), in which case you won’t have to add as much to keep your worms healthy and your bin smelling sweet.

The food in the hungry bin needs to have the right ratio of carbon to nitrogen for the bin to be most effective. The ideal carbon to nitrogen ratio for a worm farm is 20:1, however, food scraps can often have a ratio of 12:1. To balance the ratio of carbon to nitrogen, some extra material high in carbon may need to be added to the bin.

Fibrous materials are carbon rich, which also help balance the higher level of nitrogen in food scraps. Also referred to as bulk or roughage – fibre doesn’t tend to break down and rot as quickly as food scraps. It includes paper or cardboard, dead leaves, sawdust or wood shavings, vegetable stalks, old grass clippings (brown).

The bin may also develop an unpleasant smell if it has become too acidic. Sprinkle a small amount of dolomite lime or rock dust on the top layer to help reduce the acidity of the bin. Adding fibre to the food when you are putting it in the bin may also help reduce problems with acidity.