This question was asked by Jake from Lancashire, UK.
A landfill site is a place where rubbish is buried in the ground. It’s a very old way of disposing of waste; archaeologists often dig up ancient landfills that they call ‘middens’. In old times a hole would have been dug specially for putting the rubbish in, but these days rubbish is usually buried in a hole that already exists, like an old quarry. This means that instead of having to remove tonnes of soil and put it elsewhere, the rubbish just fills the hole that’s already there.
So no, burying rubbish in landfill isn’t making the Earth fatter. But rubbish that ends up in landfill instead of being recycled can take an extremely long time to break down (this is also called decomposing). A milk carton may take up to 5 years; an aluminium can can take up to 200 years to break down. Plastic will take hundreds of years and glass won’t break down for tens of thousands of years! If we keep putting rubbish into landfill sites instead of recycling or using eco-friendly alternatives then eventually we’re likely to run out of places to put it. If you’ve seen the Disney film Wall-E then you know what that might look like.