‘Green’ materials are those with high nitrogen content that are quick to rot down and add moisture to the mix. These are things like vegetable peelings, tea bags and grass cuttings.
On the other hand, ‘brown’ materials are those with high carbon content which include eggshells, cardboard and straw. Having the right balance of these is needed to maximise the quality of your compost.
The general ratio advised is three or four parts browns to one-part green, but this may need to be adjusted as some green materials are higher in nitrogen than others and some brown materials are higher in carbon than others. It doesn’t have to be exact, but having too much green material may result in a wet and smelly mixture.
You will know when your compost is ready, it’ll be a crumbly and dark material that smells earthy and fresh.