Compost Magazine

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Compost Materials That Are Just Not Compostable

Though composting your rubbish is often a good decision, composting certain types of trash can lead to more harm than good for the environment. While some trash will degrade gradually, others will refuse to break down, worsening the litter problem in landfills everywhere.

Compostable materials, or any material that naturally breaks down over a short period without emitting pollution or toxic residue, have played a part in the fight to save the environment from litter and pollution.

Due to their environmentally-friendly disposal methods, materials such as organic cotton have gained favour over non-compostable materials like synthetic fabrics in many industries.

However, not every material can go through every individual composting process. Not only are certain materials resistant or unable to be composted, but different composting systems may also utilise other methods to dispose of the material.

A lack of understanding of these systems can easily confuse the average consumer, leading to faulty waste disposal decisions.

Although it may be puzzling, it is worth examining the composting process and understanding what should or shouldn’t be included in it.

Compostable and non-compostable materials

Compostable waste consists of green and brown materials.

Green compost refers to materials containing high amounts of nitrogen, such as grass clippings, fruits, coffee, or even vegetable scraps. These materials contain moisture that allows them to rot and degrade swiftly.

Brown material, on the other hand, is rich in carbon and can be made out of paper, cardboard, yard scraps, or other dead plant matter. These materials are high in lignin, which makes it harder for microorganisms to break them down. It’s recommended to chop and tear these materials to allow them to degrade more quickly.

While some things are seemingly compostable, it’s not recommended to compost them in smaller compost systems. Meats, bones, and dairy products may degrade over time, but will also invite pathogens and unwanted insects into the compost heap.

Other materials, known as “photodegradable”, may require sunlight to break down. Most composting systems cannot expose materials to the sunlight, and thus cannot degrade these materials.

Consumers should also be mindful never to compost PFAS materials, or per- and poly-fluoroalkyl substances. This substance is often known as a forever chemical, as it seldom breaks down naturally.

As PFAS and other non-compostable materials often go unmentioned in packaging details, it’s safest to avoid composting any packaging that isn’t certified by the Biodegradable Products Institute (BPI).

Knowing your composting system

An essential factor in proper waste management is learning about your composting system. As a whole, the composting process breaks down organic waste into dirt-like material with the help of microbes. There are three systems where this may occur.

Indoor residences often use worms to break down organic waste, otherwise known as vermicomposting. Though vermicomposting can break down most food items, the worms may not process onions, garlic, or citrus peels, depending on the size of the vermicomposting system.

Some areas may provide large-scale composting systems. This system processes green waste by mixing it with carbon-rich material. The size and oxygen provided encourage rapid bacterial reproduction, which causes the material to be broken down at speed. The heat generated kills many pathogens in the process. If the compost is given enough to cure, other microorganisms enter the compost. These further purify the compost and help stop pathogens from recolonising the compost.

These large scale system can break down almost any organic material – including difficult materials such as bones, meat, or dairy products.

A smaller version of the large-scale system is the backyard compost pile. Backyard compost piles do not always have the size and structure to achieve the thermophilic temperatures needed to break down tough materials. Composting materials such as bones, meat, dairy, and faeces may attract insects, illnesses, or animals to the pile. If attempting to compost more difficult materials, it’s worth carefully monitoring the compost, using a good compost thermometer to ensure the pile reaches sufficient heat..

No matter what system is used, consumers should be mindful of the materials they do or do not compost.

Learn more about what you can and can’t compost. 

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