Composting is an ecologically beneficial practice that transforms organic waste into nutrient-rich soil amendment. Shredded paper, a readily available material from most homes and offices, serves as an excellent source of carbon, making it a valuable “brown” component for a healthy compost pile. Successfully integrating this material requires a clear understanding of which paper types are safe to use and how to properly balance and incorporate it into the composting environment. This ensures the material breaks down efficiently, contributing to a robust and productive compost.
Identifying Safe and Unsafe Paper Types
Determining the suitability of paper before shredding prevents contamination of the final compost product. Acceptable materials include standard white or pastel office paper, envelopes without plastic windows, and plain, corrugated cardboard. Non-glossy newsprint is also safe, as modern inks are typically soy- or vegetable-based and decompose without issue.
Conversely, certain types of paper must be avoided due to harmful chemical additives or non-biodegradable components. Thermal receipt paper, which has a smooth feel, should be excluded because it often contains Bisphenol A (BPA) or Bisphenol S (BPS) as color developers. These endocrine disruptors can transfer to the compost, potentially contaminating the soil. Glossy magazines, heavily dyed colored papers, and any paper treated with a plastic coating or adhesive backing must also be avoided.
Paper materials that have been laminated or include sticky labels are not suitable because the synthetic components will not fully break down. It is also important to remove any incidental contaminants, such as metal staples, plastic tape, or rubber bands, before the paper is added to the compost pile. While small pieces of metal will not harm the composting process, they will remain in the finished product and must be sifted out later.
Shredded Paper’s Role in Carbon-to-Nitrogen Balance
Shredded paper is categorized as a high-carbon material, often referred to as a “brown” in composting terminology. Carbon serves as the primary energy source for the microbial organisms—the bacteria and fungi—that perform the decomposition work within the pile. Without adequate carbon, these decomposers cannot sustain their populations or generate the heat necessary for rapid composting.
Nitrogen, the “green” material, provides the microbes with the proteins necessary for growth and reproduction. The efficiency of the composting process is governed by the Carbon-to-Nitrogen (C:N) ratio. The ideal starting ratio for rapid decomposition is approximately 25 parts carbon to 1 part nitrogen (25:1), with a successful range extending up to 30:1.
Since shredded paper has an extremely high C:N ratio on its own, it must be balanced with high-nitrogen materials to meet the microbes’ nutritional needs. Sources of nitrogen include fresh grass clippings, fruit and vegetable scraps, or coffee grounds. If the pile contains too much carbon from materials like paper, the decomposition rate slows significantly.
Techniques for Successful Incorporation
Successful incorporation of shredded paper begins with pre-treatment to initiate the breakdown process and mitigate potential problems. Paper is naturally dry and dense, making it resistant to microbial action when added directly to a dry pile. Shredded paper should be thoroughly wetted before it is mixed into the compost to speed up saturation and soften the cellulose fibers.
Wetting the paper also addresses the problem of “matting,” which occurs when dry, tightly packed paper clumps together. These dense layers create anaerobic pockets by excluding oxygen, which slows decomposition and can lead to foul odors from putrefying material. Pre-wetting the paper helps prevent it from forming these impenetrable layers, ensuring air and moisture can permeate the entire mass.
Once wetted, the paper should be added using a layering strategy, alternating thin layers of the carbon material with the nitrogen-rich “green” materials. A layer of shredded paper should be no more than two to three inches thick before a layer of food scraps or grass clippings is added on top. This technique ensures that the carbon and nitrogen sources are evenly distributed throughout the pile.
Shredded paper is also highly effective at managing excess moisture, especially when composting very wet green materials, such as many kitchen scraps. The paper acts like a sponge, absorbing free water that might otherwise lead to a slimy, anaerobic mess. Consistent turning of the pile is necessary, however, to mix the saturated paper with the other ingredients, introduce fresh oxygen, and prevent the layers from settling into a dense, matted block.