Understanding what can you put into compost is the foundational step toward creating nutrient-rich soil amendment rather than a smelly, pest-attracting mess. The core principle hinges on balancing carbon-rich "browns" with nitrogen-rich "greens" to feed the microorganisms that break down the organic matter. This balance ensures efficient decomposition, minimizes odors, and transforms kitchen scraps and yard waste into a dark, crumbly earth that gardens thrive on, turning waste into a valuable resource.
The Green Materials: Nitrogen Powerhouses
The "greens" in your compost pile provide the protein necessary for microbial growth, heating the pile to the temperatures required for fast breakdown. These materials are typically moist and soft. Common examples include vegetable and fruit scraps from your kitchen, such as peels, cores, and spoiled produce. Coffee grounds and filters contribute nitrogen without adding acidity once decomposed, while tea bags (ensure they are staple-free and made of unbleached paper) are another excellent source. Fresh grass clippings and young garden weeds, before they set seed, are potent green materials that kickstart the decomposition process.
Animal Byproducts and Kitchen Scraps
While meat, bones, and dairy products are generally avoided due to odor and pest concerns, other animal byproducts are compost gold. Eggshells, despite being hard, are an excellent source of calcium and help balance pH levels in the pile. Shells should be crushed to increase surface area for faster decomposition. Additionally, coffee filters and paper napkins soiled with food can be composted, provided they haven't been contaminated with oils or chemicals, bridging the gap between green and brown categories.
The Brown Materials: Carbon Structure
"Browns" are the backbone of your compost, providing carbon, energy, and essential structure. They are typically dry and dead plant material, allowing air to flow through the pile, which is critical for aerobic decomposition. Shredded newspaper, office paper, and cardboard (free of tape and plastic labels) are ideal carbon sources that prevent the pile from becoming a dense, anaerobic mess. Dry leaves collected in the fall are another free and abundant brown material that mimics the natural forest floor.
Wood and Natural Fibers
Wood-based materials add bulk and carbon, but they break down slowly. Small wood chips and sawdust from untreated wood are acceptable, though they should be used in moderation as they can tie up nitrogen as they decompose. Straw and hay introduce airy structure, excellent for creating air pockets, but often contain seeds that can sprout in the finished compost. Pine needles and shredded bark are acidic and suitable for acid-loving plants like blueberries, but should be used selectively to avoid altering the pH of your entire pile.
Materials to Absolutely Avoid
Knowing what to exclude is just as important as knowing what to include. These items do not break down reliably, attract vermin, or introduce toxins into your soil. Diseased plants and weeds that have gone to seed should never be composted, as the heat generated in a typical backyard pile is often insufficient to kill them. Pet waste and used cat litter carry pathogens and parasites, while glossy magazines and coated papers contain heavy metals and plastics that contaminate the final product.
The Balance: Getting the Ratios Right
Successful composting is less about precise measurements and more about maintaining a visual and tactile balance. Aim for a ratio of roughly 2 to 3 parts brown to 1 part green by volume. If your pile smells sour or becomes slimy, it is too wet and green; remedy this by adding more browns like dry leaves or shredded paper. Conversely, if the pile is not heating up and is overly dry, incorporate more greens such as fresh grass clippings or kitchen scraps. The pile should feel as moist as a wrung-out sponge to function optimally.
