Composting is a natural process where microorganisms break down organic materials into a nutrient-rich soil amendment called humus. This decomposition requires a balanced mix of carbon, nitrogen, water, and oxygen. A plastic bin can absolutely be used for composting, provided it undergoes specific modifications to create a functional aerobic environment. These simple, inexpensive containers offer a practical starting point for recycling kitchen and yard waste into valuable compost.
Why Plastic Bins Work for Composting
The popularity of plastic bins for composting stems primarily from their affordability and easy availability. Many containers, such as repurposed storage totes, are inexpensive or already on hand, making them a budget-friendly option. Plastic bins are also lightweight and portable, allowing gardeners to easily move the system as needed.
Plastic is durable and weather-resistant, protecting the compost pile from elements that can wash out nutrients or over-saturate it. The material’s non-porous nature retains heat, which accelerates the microbial activity necessary for decomposition. When selecting a container, choose plastics made from High-Density Polyethylene (HDPE, #2 symbol) or Polypropylene (PP, #5 symbol). These types are commonly used for food storage and resist chemical leaching, even when exposed to the higher temperatures that occur during composting.
Essential Modifications for Airflow and Drainage
A sealed plastic bin without modifications will quickly become an anaerobic environment, leading to foul odors and slow decomposition. The most important step for converting a storage container is drilling holes for both aeration and drainage. Oxygen is necessary for the aerobic bacteria that efficiently break down organic material. Holes should be drilled across the lid and all sides of the bin, spaced approximately every four to six inches.
The ideal hole size is small enough to contain the material but large enough to permit air exchange; a half-inch drill bit is sufficient. Drainage holes are mandatory and should be concentrated on the bottom of the bin to allow excess moisture to escape. Placing a layer of coarse, bulky material like small branches or wood chips at the bottom creates an airspace for drainage and initial air circulation. The bin must then be elevated slightly off the ground, ensuring the drainage holes remain clear and functional.
Maintaining the Composting Environment
Once the bin is physically prepared, successful composting depends on careful management of the internal environment. The microbial activity relies on a proper balance of carbon-rich “browns” and nitrogen-rich “greens.” Browns include dried leaves, shredded paper, and straw; greens include fruit/vegetable scraps and grass clippings. A ratio of two to three parts browns for every one part greens is recommended to fuel the breakdown process and prevent the pile from becoming slimy or smelly.
In a closed plastic system, the compost needs to be turned or aerated more frequently than in an open pile to replenish oxygen supplies. Turning the material every few days is beneficial, but a minimum of once a month is necessary for a functional passive system. Because the bin’s size may restrict the use of a pitchfork, a specialized winged compost aerator or a simple stick can be used to poke deep vertical holes into the material to introduce air.
Moisture levels are regulated by the enclosed container, which can trap condensation. The mixture should feel like a wrung-out sponge—damp but not dripping—which is the optimal state for microbial life. If the material is too dry, decomposition will stall, requiring the addition of water. If it is too wet, adding extra dry browns will help absorb the excess liquid and restore air pockets.
When to Avoid Using Plastic Bins
Not all organic waste is suitable for a small, passive plastic bin. Meat, fish, bones, and dairy products should be strictly avoided because their decomposition produces strong odors that draw in rodents and other unwelcome visitors. Fats and oils are also problematic as they can coat the organic material and slow the decomposition process.
Materials like pet waste, diseased plants, and weeds that have gone to seed should not be added to these home-scale systems. Small plastic composters typically cannot generate the consistently high temperatures (150°F to 160°F) needed to sterilize the compost and kill harmful pathogens or weed seeds. Finally, plastic bins that previously held harsh chemicals, solvents, or non-food-grade substances should not be repurposed for composting, as there is a risk of chemical residue leaching into the finished product.