By Jennifer Copley (Last Updated 8 March 2011)
There are two types of compost material: green and brown. Green items are nitrogen-rich materials such as kitchen scraps, fresh-cut grass, feathers, hair, and manure, whereas brown materials are dry, carbon-rich items such as shredded paper and cardboard, dried leaves and grass, peat moss, sawdust, cornstalks and cobs, and straw. Alternating layers of greens and browns will increase the likelihood of developing successful compost in a relatively short time.
Ideally, you should start with a base layer (6-10 cm) of brown materials to facilitate air circulation. Collecting and storing fall leaves is a good way to ensure a year-round supply of carbon-rich material that can be layered into the compost as needed.
The following household and garden materials are compostable:
- Coffee grounds and filters
- Dryer link (if your clothes are made from natural fibers)
- Egg shells (rinsed and crushed)
- Feathers and hair (don’t add any that have been coloured using chemicals)
- Fireplace ashes (don’t use ashes from chemically treated wood)
- Old potting soil
- Plants (don’t use weeds that have gone to seed, as you may end up adding viable weed seeds to your garden with the finished compost)
- Sawdust (don’t use sawdust from chemically treated wood)
- Shredded paper and cardboard (use only uncoated paper that is free of toxic inks and grease)
- Tea bags
- Vegetable and fruit trimmings (and rotten produce)
Chop or shred compostable materials to small pieces and layer wet and dry items. Keep the layers varied rather than adding thick layers of any one ingredient.
The microorganisms that will convert your garbage into compost require oxygen. This is why compacted materials in landfills take ages to decompose, and why they produce methane (a greenhouse gas) in the process. To avoid these problems, leave a little space for air in the compost bin and turn the materials over once a week (or at least every 2 weeks) to mix and aerate them.
Items That Should Not Go Into the Compost Bin or Pile
There are a number of kitchen items that will cause the compost to smell foul and attract rodents and other pests. Such materials, which are also very slow to break down in the composter, include:
- Baked goods (breads, cakes, muffins, etc.)
- Dairy products
- Grease/oil/fat (and paper towels contaminated with oily substances)
- Sauces and salad dressings that contain fats, oils, dairy, or meat
Items that shouldn’t be composted due to their toxic content include:
- Ash from coal or barbecues
- Chemically treated wood products
- Glossy coated paper
- Most types of kitty litter
- Metallic wrapping paper
Other items that can be harmful if composted include seeds of aggressive weeds, which will later grow in the garden after the compost is used, and diseased plants, as there is a risk of spreading disease back to new plants when the compost is used.
As for composting pet waste, there are safety issues and experts are divided as to whether or not this is a safe practice. For more on this, see Is It Safe to Compost Pet Waste?