What You Can and Can't Compost

All appropriate compost ingredients are organic.  Organic refers to matter that is a part of, or comes from, something that is (or was) alive.  In other words, organic refers to plants, animals and their naturally-occurring by-products.

Compost Only Organic Materials

Nature has a cycle for animals and plants.  When they die, they decay.  Their decaying forms provide food for fungi and bacteria, which provide food for other microorganisms, which provide food for bugs, which provide food for frogs, which provide food for larger and larger creatures throughout the food chain.

Decomposing remains also provide nutrients and structure-building materials to the soil so that plants have a healthy, nutrient-rich environment in which to grow.  Composting encourages this transformation from decay of dead forms into food for soil creatures and plants.

Inorganic materials do not decompose in this way and should be kept out of the compost bin.

Do NOT compost inorganic materials such as:

  • Plastic
  • Styrofoam
  • Aluminum or other metals
  • Glass
  • Rocks

DO compost appropriate organic waste:

  • Shredded paper
  • Grass clippings
  • Leaves
  • Horse or cow manure
  • Coffee grounds and filters
  • Newspaper
  • Tea leaves and bags
  • Eggshells, crushed
  • Hay or straw
  • Garden wastes, flowers, yard trimmings
  • Pine needles and cones
  • Shredded cardboard
  • Sawdust
  • Nut shells, acorns
  • Seaweed
  • Peanut hulls
  • Spent beer or wine
  • Flat soda or sports drinks

There are organic materials that should not be composted at home for various reasons, including health, odour, and safety.  These materials will decompose, but a home composting system is too small to address problems created as they decay.  Effective composting of these materials generally requires the higher temperatures, professional monitoring, and odour control techniques of large-scale composting.

Do NOT compost inappropriate organic materials:

  • Oil
  • Grease
  • Dairy
  • Meat
  • Cat or dog faeces
  • Diseased plants
  • Weeds that have gone to seed (actually, it’s the weed seeds you should avoid, the rest of the plant is OK)
  • Road kill or other dead animal
  • Organic poisons like boric acid
  • Rubber
  • Coal, charcoal
  • Human feces (except in composting toilet systems specifically designed to handle this waste safely)

Take Your Unique Needs Into Account

You should always take your household needs and safety into account.  Pine needles and cones were listed as an acceptable material for home composting earlier in this article.  However, you should not use a load of needles and cones if you are allergic to pine, or children who will be playing on a lawn fertilized with the finished compost are allergic to pine, or if someone has sprayed the pine tree with pesticides.