Compost heaps are a great way to recycle kitchen scraps and garden waste. But they need air to work properly. Without air, the heap can turn smelly and slimy. This happens because the wrong types of microorganisms take over. Microorganisms are tiny living things that break down organic matter. They are the main workers in a compost heap. When you add air to a compost heap, you help the good microorganisms grow. These microorganisms need oxygen to survive. They break down the waste quickly and produce heat. The heat helps to kill weed seeds and plant diseases. A well-aerated compost heap also produces rich, dark humus. Humus is the final product of composting. It is full of nutrients that plants love. To keep your compost heap healthy, you should turn it regularly. Turning mixes the materials and adds air. You can also add bulky items like twigs or straw to create air pockets. If your compost heap smells like rotten eggs, it probably needs more air. The smell comes from bacteria that work without oxygen. These bacteria are not as good at breaking down waste. In summary, air is essential for good composting. It helps the right microorganisms decompose the waste efficiently. The result is nutrient-rich compost that improves your garden soil.

Key vocabulary for this lesson: microorganism.