In Harrow, you cannot compost items that aren't permitted in the food waste caddy. The caddy is specifically for food waste like raw and cooked food, fruit and vegetable peelings, dairy, eggshells, bread, pastries, meat, fish, bones, tea bags, coffee grounds, rice, and pasta. However, you should not include any packaging, garden waste, or liquids.
If you're interested in understanding more about waste management, check out the details on Harrow's waste and recycling information.