How to keep rats out of your compost

Composting doesn’t generally attracts rats in the first place, but if rats are already present in your garden, they may visit the compost heap. Some rats can carry the bacteria that cause leptospirosis (aka Weil’s disease), which is spread via their urine. While the chances of infection are low, it’s a good idea to take action to keep rats out of your compost.

What are the signs of a rat infestation?

  • Rat tunnels at the base of the compost bin or in the soil. These tunnels have about a 30mm diameter.
  • Holes and chew marks in the bin

Which container should I use?

To avoid rats getting into your compost bin, it’s best to use an enclosed container such as a wormery, an indoor bokashi bin, a tumbler or a hot bin. If using a plastic bin, buy one with a base and a tight fitting lid. If you have a dalek bin without a base, you can prevent them from burrowing under by placing the bin on concrete, gravel or pebbles and lining the base with a thick wire mesh (not chicken wire as rats can chew through this).

Pallet bins and open heaps are unsuitable as they provided easy access.

Which compost ingredients attract rats?

Unless your bin is fully enclosed, you should avoid adding cooked food, meat, fish and dairy as these are particularly appealing to rats. Apparently, so are egg shells and potato peels!

Hot composting

Temperatures above 37C° will kill Leptospira, the bacteria in rat urine which causes Weil’s disease. Therefore, it is unlikely to survive if you are using a hot composting method which will reach temperatures of 40-60˚C.

It is worth noting that once hot compost has cooled and is left to mature (finish decomposing), Leptospira could survive in the pile, so it’s best to make sure rats can’t access the pile during this stage. More info about hot composting.

Other top tips for deterring rats:

  • Make sure your compost contains enough moisture, as a dry compost pile is an ideal nesting site and shelter for rats.
  • Turn the contents regularly – you should do this anyway to introduce air, but it has the added benefit of deterring rats from using it as a nesting site.
  • Rats like to move around where they cannot be seen, so situate your bin in the open away from walls or fences.

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