Tony O’Neill, gardener and author of the popular “Composting Masterclass” and “Your First Vegetable Garden,” combines lifelong passion and expert knowledge to simplify the art of gardening. His mission? Helping you cultivate a thriving garden.
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Traditional composting is the managed decomposition of organic matter that mainly consists of food waste, brown plant material, and fresher green plant material.
While all organic matter will eventually decompose, we must carefully consider what we add to our compost pile. Organic materials that will attract rodents and pests should be avoided, as well as infected materials and those that contain weed seeds that need higher temperatures.
Table of Contents
What Not to Put in Compost and Why
Inert Materials
These materials are not biodegradable and will merely pass through the process unchanged, eventually polluting the soil to which the compost is added.
- Chemical-synthetic residues, adhesives, solvents, petrol, lubricants, paint
- Non-degradable materials (glass, metals, plastics).
- Foil wrappers Styrofoam (plates, cups, etc.)
- Plastic utensils (forks, spoons, knives, plates, cups, stir sticks, lids, etc.)
- Single-serve containers (ketchup, butter, jelly, jam, cream, etc.)
Contaminated Organic Materials
Wood is commonly chemically treated to extend its durability, mainly the onslaught of organisms that will cause its decay.
When added to compost, these same preservation materials scupper the growth and development of essential composting microorganisms.
- Agglomerate or plywood
- Painted wood
- Sawdust from treated wood
- Transport pallet wood
- The timber used in mining operations
Materials That Contain Biocides
Some organic materials have biocidal properties to defend them against natural microorganic threats.
Then there are also the chemicals we’ve developed to fight bacteria (sometimes nothing more than a perceived risk).
- Tobacco since it contains a potent biocide such as nicotine and various toxic substances.
- Cedarwood
- Detergents, chlorinated products, antibiotics, and drug residues.
- Flowers sold commercially – treated with antibacterial preservatives
- Walnut shells and Black Walnut leaves
- Equine or bovine manure from farms that treat their feed crops with Aminopyralid
- Lawn clippings if you use a broadleaf herbicide that contains Clopyralid
- Herbicides from the Bipyridyliums family also have low microbial decomposition rates. Gramaxone and Diquat are examples.
- Persistent Herbicides
Animal Products
Animals should be incinerated or sent to special facilities for decomposing animal carcasses.
- Any animal carcasses
- Cooked leftovers, specifical meat
- Feces of carnivores
My Book Composting Masterclass Is Available Now!
So many people struggle to make compost. It either takes an eternity to break down or becomes a smelly mess. I wrote this book so that you can learn what happens in your compost pile at the microscopic level and the fundamentals. Knowing this will allow you to understand at what stage your compost is, solve problems, and find solutions when making compost. Check out what others say about the book!
The most comprehensive book on composting I have ever read!
I thought I knew something about composting organic materials to use back in my garden as “black gold.” Still, Tony’s breaking down (pun intended) composting principles and methods has given me a better understanding of the whole process.
If you want to know everything about composting and becoming a Compost Master – read this book!
Mark Valencia (Self-Sufficient Me)
How to Deal with Pathogens and Weed Seeds
Human, canine, and feline waste should not be added to the compost pile as it may allow disease transmission.
The compost pile should not contain sick plant matter or weeds that have gone to seed.
We can achieve temperatures as high as 170 degrees Fahrenheit if water, air, insulation, pH, carbon, and nitrogen elements are closely managed.
Most disease pathogens and weed seeds are destroyed at temperatures above 150⁰F (65⁰C).
Sadly, most residential compost piles seldom reach temperatures where pathogens and weed seeds are destroyed.
These temperatures will be achieved only in insulated compost bins where batches are close to a 30:1 ratio of carbon to nitrogen, kept moist, and turned regularly.
As a result, the composting process does not eliminate disease germs and weed seeds.
If unhealthy plant components are composted, the finished product should not be used in the same spot in the yard as it was created.
Since animal fats and bones are difficult to compost and can attract dogs, rodents, and other animals, they shouldn’t be included in the compost pile.
What Can be Composted
The vast majority of organic materials are compostable. Below there is a list of materials that can be composted:
Gardening Waste
| Grass clippings | Shrub Trimmings |
| Leaves (shredded) | Tree Trimmings (Mill thicker branches) |
| Weeds | Potted plants |
| Flowers | Yard Debris |
Kitchen Scraps
| Vegetable scrap | Freezer-burned vegetables and fruits |
| Expired fruit | Dregs from juice, beer, wine |
| Eggshells | Nutshells (excluding Walnut) |
| Coffee grounds | Bread, tortillas, pitas |
| Tea leaves (not the teabag) | Cereal and crackers |
| Peels (Including Citrus) | Chips (tortilla, potato, etc.) |
| Spoiled food | Cooked pasta, rice, and other grains |
| Wine corks | Almond, Soy, Rice, and Coconut milk |
| Toothpicks |
Household Waste
| Hair and fur | Dead blossoms |
| Dryer lint | Bamboo skewers |
| Vacuum contents & floor sweepings | Potpourri |
| Pencil shavings | Beer and wine-making leftovers |
| Loofahs (the organic type) | Evergreen garlands and wreaths |
| Cotton, wool, linen, silk, hemp, burlap, felt | Jack-o-lanterns |
| Used matches | Dry dog, cat, and fish food |
| Indoor plant trimmings | Crepe paper streamers |
| Nail clippings | Yarn, thread, string, rope, twine |
| Aquarium water, algae, plants | Cork Board |
| Spent potting soil |
Paper Products
| Shredded paper | Uncoated paper cups & plates |
| Food-soiled paper or cardboard | Compostable bags made from plant starches |
| Cardboard | Paper baking cups |
| Plant starch compostable containers, dishware & utensils | Paper table cloths |
| Paper bags | Cereal boxes |
| Paper towels and toilet paper cores | Paper egg cartons |
| Tissues, paper napkins, and paper towels | Pizza boxes |
| Wrapping and tissue paper (no ribbons, foil, or tape) |
Wood Product (from untreated wood)
| Wood shavings | Shredded wood |
| Sawdust | Bark |
Manures (Herbivores)
| Bovine (Cattle) – see exclusion list above | Sheep |
| Equine (Horse) – see exclusion list above | Alpaca |
| Rabbits | All herbivores |
| Chicken | Turkey Litter |
| Goat | Swine Manure |
Acquired Farm Products
| Hay | Lucerne |
| Teff | Corn Silage |
| Straw |
In Conclusion
Many more materials are permitted in a compost pile than those not. Some of these are inert and unable to affect the outcome, and others will ruin the batch and should be avoided at all costs.
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