Compost Troubleshooting

From not the right mix to unwanted visitors, find out how to fix common home composting issues here.

Getting the right recipe

To have a successful compost heap, you need to ensure you get the right mix of both brown dry material (cardboard, leaves, egg shells) and green wet material (garden trimmings, peelings and pulps). It’s important that this balance is kept to prevent your heap from becoming too wet or too dry:

Wet, slimy and strong-smelling compost

Too little air and too much water are often to blame. Cover the heap to protect against rain and add more brown waste, such as chopped woody material, shredded woodchip, straw or paper (source Composting / RHS Gardening).

Dry and fibrous with little rotting

Usually caused by too little moisture and too much brown material. Add more green waste (e.g. grass cuttings, hedge trimmings, old flowers, fresh leaves), or try a commercial activator or accelerator such as ‘Garotta’.

Alternatively, add fresh manure at one bucket for every 15cm (6in) layer of compost, fish, blood and bone fertiliser at 270g (9oz) per 15cm (6in) layer of compost or sulphate of ammonia fertiliser at 140g (5oz) per 15cm (6in) layer of compost (source Composting / RHS Gardening).


If rats are regularly visiting your compost bin, the following deterrents may help:

  • Sit the bin on heavy duty mesh or chicken wire (maximum 6mm x 6mm hole)
  • Regularly turn the compost to ensure all food is incorporated
  • Ensure the bin is set squarely and level so that there is no gap between the sides and the lid.
  • Rats don’t like disturbance. Putting the bin somewhere you pass by often and giving it a good rat-a-tat on the side with a stick every time will discourage them from taking up residence.
  • Use a ‘green cone’ instead
  • Use a wormery instead – click here for more information
  • Sit the bin on an aluminium sheet with holes in (6mm x 6mm)
  • Grow mint around the bin
  • Don’t put cooked food, dairy or fish in bin if it gets bad
  • Last resort – only use your compost bin for garden waste


Well-run compost bins don’t produce swarms of flies, but if you do see these, then make sure you cover kitchen waste with garden waste after adding it to the heap and check that moisture levels are not too high, causing insufficient air in the heap (source Composting / RHS Gardening).