Why is my compost bin smelly or not breaking down?

In New Zealand, a smelly or underperforming compost bin usually points to a few predictable issues — and all are fixable by balancing moisture, air, and the right types of material. First, make sure you're layering the right mix: about 30% “greens” (food scraps, grass clippings) and 70% “browns” (dry leaves, shredded cardboard). 

If your compost bin is too wet and stinky, it may lack enough brown material or air. Try turning the top layers, adding more dry material, and improving airflow. For slimy or slow‑decomposing compost, it could be that there’s not enough nitrogen (greens), or that the pile needs more turning. 

Pests like rats often come when cooked foods, meat, or oily scraps are added — avoid these. Also, to reduce odours, place your bin in a sunny spot to help dry it out and encourage decomposition. 

Finally, patience is key. In NZ gardens, compost can take 6‑9 months to fully mature, depending on temperature, moisture, and how well you maintain the pile.