When compost goes bad.

So your compost is soggy. Usually you can blame one of three things.

  • poor aeration
  • too much moisture
  • not enough carbon-rich material

Let's look at aeration. It you've been chucking in loads of grass clippings and heaps of fallen leaves, this can get really dense and your compost pile literally can't breathe. It has to breathe, because this is what helps the aerobic organisms to do their job and break it down. No air means anaerobic organisms get to work instead, who will still break it down, but it will take years. No-one wants that.

How to fix it: Turn your heap; stick a fork right in the middle and lift and turn what you've got in there. It will help move things around and make air holes.

But why is it wet? If your bin is the wrong side of moist, it’s very likely you are putting in too much nitrogen rich material. By this we mean lots of fruit and vegetable waste along with your grass. Adding fruit and veg waste is good, but not on its own. It will just rot into a soggy mess.

How to fix it: Add your fruit and vegetable leftovers, but add other things too!

So what do we mean by not enough carbon. All the things you put in a compost bin are either nitrogen rich (usually called “the greens”) or carbon rich (commonly called “the browns). And to get the best compost you need both. As we’ve said above, if you put in too much of one thing, it won’t work. Or will take a very, very, very long time.

How to fix it: Carbon material includes things like torn up paper and card (egg boxes, loo rolls, kitchen rolls), tea bags, coffee grounds, crushed egg shells, plant stems, twigs and shredded woody trimmings.

See our compost A-Z for a full list of what you can add. Try to aim for a 50/50 split if you can.


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