Most plain, unprinted paper used for cushioning packages is readily compostable. This material, often called kraft paper or void fill, is made primarily from wood pulp and contains the cellulose fibers necessary for microbial breakdown. However, compostability depends entirely on the absence of non-paper contaminants associated with shipping. Before adding packing paper to a compost pile, inspect and prepare it carefully to ensure it decomposes efficiently and safely.
Identifying Compostable and Non-Compostable Paper
The suitability of packing paper for composting is determined by what has been added to the paper fibers. Plain, brown kraft paper and unbleached, uncoated tissue are safe additions because they consist of simple cellulose fibers and natural lignin. These materials break down fully without leaving behind toxic residues or microplastics that compromise the finished compost.
Common elements that render paper uncompostable include plastic coatings, glossy finishes, heavy-duty adhesives, and certain inks. Avoid any paper that feels slick, waxy, or shiny, as this indicates a synthetic polymer coating, such as polyethylene, which does not biodegrade. These coatings separate into microplastic fragments during composting, contaminating the organic matter.
A simple water test can identify coatings: sprinkle a few drops of water onto the paper and observe the absorption rate. If the water beads up or is absorbed very slowly, the paper likely has a water-resistant coating and should be recycled instead of composted. Furthermore, all non-paper elements must be fully removed before composting, including plastic tape remnants, shipping labels, and metallic staples.
Brightly colored inks and dyes can be problematic, as vibrant or fluorescent colors may contain heavy metals or synthetic chemicals unsuitable for an organic compost mixture. While many modern black and brown inks, particularly those on plain cardboard, are soy-based and safe, it is best practice to avoid paper with heavy, colorful printing. When in doubt about a colored or glossy piece of packing paper, dispose of it through the recycling bin to prevent contamination.
Preparing Packing Paper for the Compost Bin
Once the packing paper is confirmed free of contaminants, physical preparation ensures rapid decomposition. Paper in large sheets or crumpled balls resists moisture and creates dense, matted layers, slowing the work of microorganisms. To prevent matting and speed up the process, the paper’s surface area must be significantly increased.
The most effective method is to shred or tear the paper into small pieces, ideally into strips no larger than one or two inches. This reduction in particle size exposes more cellulose to the microbes responsible for breaking down the material. Shredding also helps the paper integrate thoroughly with other materials, avoiding the formation of large, slow-to-decompose clumps.
After shredding or tearing, the paper should be thoroughly wetted before it is added to the compost mixture. Dry paper absorbs moisture from the surrounding compost, which can dehydrate the microbial colonies and stall the decomposition process. The shredded paper should feel like a damp sponge—moist all the way through, but not dripping with excess water—to provide the optimal hydration level for the decomposers. This pre-moistening step ensures the paper immediately becomes an active component of the compost.
The Functional Role of Paper in the Composting Process
Packing paper serves a beneficial function within a compost pile by contributing carbon, which is necessary to fuel the decomposition process. Paper is classified as a “brown” material, distinguishing it from nitrogen-rich “green” materials like food scraps and fresh grass clippings. Microorganisms require a balance of carbon for energy and nitrogen for protein synthesis to thrive and efficiently break down waste.
The ideal Carbon-to-Nitrogen (C:N) ratio for an active compost pile is around 25:1 to 30:1. Since paper is high in carbon, adding it helps balance the high nitrogen content of kitchen waste. Without sufficient carbon, excess nitrogen is released as ammonia gas, leading to unpleasant odors and a less efficient system.
Beyond its chemical contribution, the physical structure of shredded or crumpled paper improves the pile’s overall structure by acting as a bulking agent. This material helps create small air pockets, which promotes aeration and allows oxygen to circulate throughout the compost. Oxygen is essential for the aerobic bacteria that generate the heat needed for rapid composting; insufficient airflow causes the pile to become anaerobic, leading to a slow, smelly process.