11. Mar, 2020

Rats in Compost bins

The photo shows two “rats” in a compost bin, on our Stokes Wood Allotment Demonstration site, containing too many Browns and consequently offering a nice dry and comfortable home. In practice rat infestation is often associated with food being put in a bin which is not rat proof.
When rats are feeding, sheltering or nesting in a compost bin burrows can often be seen under the bin or holes are visible chewed into the side of the bin. The signs of their presence in the rest of the garden are also relatively easy to detect
The location of the bin can increase the risk of rats taking up occupation. As the brown rat prefers to move along runs close to walls, fences hedges, etc the bin should be positioned in the open away from potential rat runs. Leaving an open space round the bin also makes it easier to check for future burrows. As black rats like trees and shrubs it is best to place the compost bin away from these and if trees do overhang the bin cut the branched so that they do not provide a means of reaching the bin.
It is generally accepted that rat infestation of the compost bin will be linked to the composting of bread, cooked foods, dairy products, fish, meat, fatty and processed foods. Some composters even recommend washing eggshells to reduce the smell before adding them to the bin. While all of these are undoubtedly attractive to rats other kitchen waste such as fruit and vegetable peelings also provide appetizing meals once the rats have gained access. It seems that rats are quite keen on potato peelings and the smell of decomposing fruit certainly seems to attract rats to many school compost bins and food digesters
The is some anecdotal evidence that the number of times the heap is disturbed can influence whether it becomes infested by rats. It is certainly true that rats do not like frequent or continued disturbance. Putting the bin near the house or garden path that is used regularly and knocking, kicking or hitting the bin with a stick every time it is passed certainly make it a less desirable residence for rats. Regular aeration of plastic bins using a commercially available compost aerator or garden fork is also helpful as it disturbs the deeper layers of compost.
Rats frequently gain access to the bin though the soil on which it is stood. There are several ways in which this risk can be reduced by:

  • Laying a solid concrete base
  • Paving slabs can also be used to provide a less permanent solid base. These must be laid touching each other so that the rats cannot gain access between them.
  • Standing the bin on a layer of pebbles to make it more difficult for the rats to burrow below or round the bin.
  • A weldmesh or plaster mesh base can be fitted across the bottom of the bin.
  • If buying a plastic bin, choose one with a base (they may be sold as an extra) or choose a tumbler bin which is located up of the ground.
  • If using a wooden bin, a solid-sided bin is obviously more secure than an open-slatted one. Wooden but open-slatted bins can be made rat proof by lining the inside with wire mesh (weldmesh is probably better than wire netting.

More information rats in compost is given at http://www.carryoncomposting.com/416920198.
Details of our next Introduction to composting training session is given at http://www.carryoncomposting.com/443725783