What Not to Put in Compost: A Comprehensive Guide

Imagine a heap teeming with life, breaking down food scraps and yard waste into nutrient-rich compost – the black gold of any gardener. But what happens when that carefully constructed ecosystem goes awry? Quite often, the culprit isn’t what is there, but what shouldn’t be. Knowing what not to put in compost is just as crucial as knowing what to include, ensuring a healthy, productive compost pile that will enrich your garden for years to come.

The Foundations of Composting: The Good, the Bad, and the Ugly

Composting is, at its heart, a natural decomposition process driven by microorganisms. These tiny workers need the right balance of ingredients to thrive and efficiently break down organic matter. Think of it like baking a cake: too much of one ingredient can throw off the whole recipe. In the composting world, we’re aiming for a harmonious blend of greens (nitrogen-rich materials) and browns (carbon-rich materials), along with adequate moisture and air. But even with the perfect balance, certain items can sabotage the entire operation.

Meat, Poultry, and Fish: A Recipe for Disaster

One of the most common mistakes is adding meat, poultry, or fish scraps to the compost pile. While technically organic, these materials present several problems:

• Odor: Decomposing meat emits a foul odor that can attract unwanted visitors like rodents, flies, and even larger animals.
• Disease: Meat scraps can harbor harmful pathogens that may not be fully eliminated during the composting process, potentially contaminating your garden.
• Slow Decomposition: These materials break down much slower than plant-based scraps, disrupting the balance of your compost pile.

The same goes for bones and fatty food waste. Bones take an incredibly long time to decompose, and fats can create an anaerobic environment, hindering the composting process and producing unpleasant smells. Keep these out of your compost at all costs!

Dairy Products: Another No-Go

Similar to meat, dairy products like milk, cheese, yogurt, and butter should be avoided. They also attract pests and can create unpleasant odors . Dairy products are high in fat, which can slow down decomposition and lead to anaerobic conditions.

Oils and Greases: A Slippery Slope

While small amounts of vegetable oil might seem harmless, larger quantities of oils and greases can be detrimental to your compost. They coat organic matter, preventing air and water from penetrating, which suffocates the beneficial microbes. Like fats, oils can also turn your compost pile anaerobic and attract pests. Save your waste oil for recycling programs instead.

Pet Waste: A Health Hazard

Dog and cat feces, as well as kitty litter, are definite no-nos for composting. These materials contain harmful bacteria, parasites, and pathogens that can survive the composting process and pose a serious health risk if the compost is used on edible plants. While specialized hot composting systems can potentially eliminate these pathogens, it’s best to err on the side of caution and dispose of pet waste properly.

Diseased Plants: Spreading the Problem

Avoid adding diseased plants or plant parts infested with pests to your compost pile. The composting process may not always kill off all the pathogens or pests, and you could end up spreading them throughout your garden when you use the compost. Instead, dispose of diseased plants in the trash or burn them (where permitted).

Chemically Treated Materials: Contamination Concerns

Be wary of adding materials treated with pesticides, herbicides, or other chemicals to your compost. These chemicals can persist in the compost and potentially harm your plants or contaminate the soil. This includes:

• Treated wood: Avoid adding pressure-treated lumber scraps, as they contain chemicals that can leach into your compost.
• Weeds treated with herbicides: These can contaminate your compost and prevent seeds from germinating.
• Coal ash: May contain heavy metals that can be harmful to plants and humans.

Persistent Weeds and Invasive Species: A Spreading Nightmare

Certain weeds, particularly those with persistent root systems or prolific seed production, should be kept out of your compost pile. Their seeds or root fragments can survive the composting process and sprout in your garden, turning your compost into a weed farm. Examples include bindweed, Bermuda grass, and quackgrass. Similarly, avoid composting invasive species, as you risk spreading them further.

Black Walnut: A Toxic Threat

Black walnut trees produce a substance called juglone, which is toxic to many plants, particularly tomatoes, peppers, and eggplants. Avoid composting black walnut leaves, twigs, or hulls, as the juglone can persist in the compost and inhibit the growth of susceptible plants.

What About… Questionable Items and Considerations

Some items fall into a gray area when it comes to composting. Whether or not to include them depends on your composting system, your level of experience, and your comfort level.

Citrus Peels

Citrus peels can be added to compost in moderation. They are highly acidic, and very large quantities can disrupt the pH balance of your compost. Chop them into small pieces to speed up decomposition.

Onions and Garlic

Similar to citrus, onions and garlic can be added in small amounts. They contain allium compounds that can be antimicrobial, potentially affecting the beneficial microbes in your compost if used in excess.

Bread and Grains

Bread and grains can attract pests, especially rodents. If you choose to compost them, bury them deep in the pile to minimize odors and deter animals [externalLink insert].

Glossy Paper and Cardboard

Avoid glossy or coated paper, as it may contain inks or coatings that are harmful. Plain paper and uncoated cardboard can be composted, but tear them into small pieces to speed up decomposition.

Best Practices for Successful Composting

Knowing what not to put in your compost is only half the battle. Here are some best practices to ensure a successful and productive compost pile:

• Maintain a Proper Green-to-Brown Ratio: Aim for a ratio of approximately 1 part green materials to 2-3 parts brown materials.
• Chop Materials into Small Pieces: Smaller pieces decompose faster.
• Aerate Regularly: Turn your compost pile every few days to provide oxygen for the microbes.
• Maintain Adequate Moisture: The compost should be moist like a wrung-out sponge.
• Monitor Temperature: A hot compost pile (130-160°F) will kill off most pathogens and weed seeds.

Conclusion: Composting with Confidence

Composting is a rewarding way to reduce waste, enrich your garden, and connect with nature. By understanding what not to put in your compost, you can avoid common pitfalls and create a thriving ecosystem that transforms waste into valuable fertilizer. So, compost with confidence, knowing you’re creating black gold while protecting your garden and the environment!