Pencil shavings are generally compostable, making them a useful addition to a home composting system. The primary components of a standard pencil are derived from natural materials that can break down. Understanding the different parts of the pencil is necessary to ensure you are adding only beneficial materials to your pile. By separating the wood from potentially problematic contaminants, you can successfully divert this common waste product from the landfill.
Analyzing the Materials in Standard Pencils
The bulk of a pencil shaving comes from the wood casing, which is an excellent source of “brown” material for composting. This wood is high in carbon, which is needed by the microorganisms in the pile for energy. The small, thin nature of the shavings is beneficial because the increased surface area allows microbes to break down the cellulose and lignin more rapidly than they would a solid piece of wood. Wood is considered a high-carbon material, often having a carbon-to-nitrogen (C:N) ratio similar to that of sawdust, which can range from 200:1 to 500:1.
The central part of the shaving is the pencil “lead,” which is not the toxic metal lead, but a mixture of powdered graphite and clay. Graphite is a stable, crystalline form of carbon that is largely inert and will not decompose through microbial action in a compost pile. Clay, which is a naturally occurring mineral, is also inert and will not break down. Both of these materials are harmless and will simply integrate into the final compost, becoming part of the mineral structure of the finished soil without causing contamination.
Identifying and Managing Non-Compostable Elements
While the wood and the core are safe, the outer coating of a standard pencil requires some consideration before composting. Many modern pencils are coated with paint or lacquer for color and a glossy finish. These finishes are often non-toxic and water-based, but heavily applied coatings or older lacquers can contain synthetic materials that may not break down or could introduce undesirable chemicals. If you are unsure about the paint’s composition, it is advisable to limit the amount of heavily painted shavings added to the compost.
Colored pencils present a greater concern for composters because their cores contain waxes, binders, and pigments. These additives may not be biodegradable and can introduce persistent synthetic dyes into the final product. Unless a manufacturer specifically confirms that a colored pencil is made with non-toxic, all-natural, and compostable dyes and binders, those shavings should be avoided. Additionally, any metal ferrules (the bands holding the eraser) or plastic caps must be removed entirely before composting any part of the pencil.
Practical Steps for Adding Shavings to Your Pile
The high carbon content of wood shavings classifies them as a “brown” material, which must be balanced with nitrogen-rich “green” materials, such as food scraps or grass clippings. The ideal carbon-to-nitrogen ratio for active composting is between 25:1 and 35:1. Since wood shavings are far higher in carbon, they should only be added in moderation relative to the overall volume of the pile. This prevents the decomposition process from slowing down excessively.
It is helpful to mix the pencil shavings thoroughly with the green materials rather than dumping them in a single clump. This even distribution helps prevent the highly carbonaceous wood from forming dense layers that can inhibit airflow and moisture penetration. The shavings are typically very dry and will absorb moisture from the pile, so they should be added when the compost is slightly wetter than the ideal consistency of a wrung-out sponge. You can also moisten the shavings lightly before adding them to ensure they are not robbing necessary water from the microbial population.