Gibby's Garden: List of Good and Bad Compost Ingredients

What can and cannot go into a compost pile? This question is probably more common than you think and it’s one that I’ve thought about myself. Many gardeners stress about whether or not what they are adding to their compost piles is good, organic and or even safe.

To make things a little easier and less stressful, I consulted Rodale’s “Make Compost in 14 Days” guide and put together a list of compost ingredients that are good, bad and okay in moderation. I wanted to consult the pros and provide you with an excellent and trustworthy reference to ease any composting fears you may have.

Why do Compost Ingredients Matter?

A healthy compost pile has lots of scraps that contain nitrogen and/or carbon. Both of these compounds help the pile breakdown creating nutrient rich compost.

Examples of Carbon Rich Ingredients

Microbes, those tiny guys that breakdown compost ingredients, feed on carbon. Carbon provides them with energy to do their work.Carbon rich ingredients are “brown” ingredients. This includes organic matter that is dry and brown or yellow in color.

Dead Leaves
Straw
Dead Flowers
Corn Stalks
Brown Garden Debris
Hedge Prunings
Twigs
Pine Needles
Straw

Examples of Nitrogen Rich Ingredients

Nitrogen rich ingredients are important because they provide microbes with protein. Protein helps them to bulk up and get the job done. Nitrogen rich ingredients are “green” ingredients. These include organic matter that is moist.

Green Leaves
Fresh Grass Clippings
Plant-Based Kitchen Scraps
Chicken/Horse Manure
Aquarium Water/Algae/Plants (fresh water only)
Dead House Plants
Green Garden Debris

Good Compost Ingredients

Anything that goes into your compost pile should be biodegradable, meaning it needs to be able to breakdown naturally. This includes most plant materials and lots of kitchen and yard scraps. Before tossing ingredients into your compost pile make sure they are free of chemicals, diseases and toxins.

Plant Materials (disease, toxin & chemical free) *
Kitchen Scraps (no meat or dairy products - this includes bones)
Leaves
Twigs
Grass Clippings
Pine Needles
Straw
Garden Debris
Fresh Water Aquarium Water/Algae/Plants

* Any diseased materials or those containing toxins and chemicals must be kept out of the compost. Disease and other toxins can leach into your compost making for an unhealthy garden and inedible fruits and vegetables.

FYI - Did you know that rhubarb leaves are poisonous? Keep these out of the compost but go ahead and add the stalks and peelings.

Bad Compost Ingredients

If you don’t know whether something is biodegradable or chemical and toxin free, don’t add it to your compost. Why take the chance? Also, if any of your yard scraps, i.e. weeds have gone to seed, meaning their seeds have developed, keep those out of your compost as well. Most weed seeds will have no problem establishing themselves in the garden once the compost has been applied.

Diseased Plants/Garden Debris
Domestic Animal/Reptile Manure (this includes pig manure) *
Paper (anything glossy or printed with color)
Meat
Bones
Dairy Products
Black Walnut Leaves/Bark/Chips (naturally contains a chemical called juglone which slows or stops plant growth)
Gypsum Board Scraps (may contain toxins or paints)
Plant Materials not from Your Yard (only put materials from your yard into your compost to ensure they don’t contain any chemicals or toxins)

* Horse and chicken manure are safe to add to your compost. These are great organic ways to add nitrogen. Other types of manure can contain parasites or harmful pathogens that can make you sick. STAY AWAY from these.

Okay Compost Ingredients

The list of “okay” compost ingredients should only be added to the compost pile in moderation or in certain ways. Most of these ingredients breakdown very slowly and some may even contain elements that aren’t biodegradable. Though these items can be added infrequently in small amounts, you can forgo them all together if it makes you more comfortable.

Cardboard: Shred or chop it up first to help it breakdown faster.
Black & White Newspaper: Shred it first.
Dryer Lint: Can contain non-biodegradable fibers.
Human/Pet Hair: Takes a long time to decompose, doesn’t hold water and mats.
Sawdust: Must be untreated. Can hog nitrogen.
Vacuum Bags: Can contain non-biodegradable fibers and other items.
Wood Ash: High in alkalinity. Remember, not all plants grow well in alkaline soil.

For the best results, your compost pile should have a 30:1 carbon to nitrogen ratio. This helps the pile breakdown at a steady pace without emitting a funky odor. Compost piles with too much nitrogen start to stink and piles with too little carbon take longer to decompose.

The folks at Organic Gardening suggest adding 1 part nitrogen rich ingredients such as grass clippings to 2 parts carbon rich ingredients such as dead leaves to keep your compost pile decomposing at the right pace.