Improper disposal of old or unwanted fertilizer introduces high concentrations of nutrients, particularly nitrogen and phosphorus, into the wastewater system or local waterways. This nutrient overload can cause excessive algae growth, known as algae blooms, in rivers and lakes, depleting the dissolved oxygen that aquatic life needs to survive. Furthermore, chemical components in fertilizers can contaminate groundwater, a source of drinking water, with excess nitrates that are harmful to infants.
Identifying the Type of Fertilizer You Have
The proper method for disposal depends entirely on the fertilizer’s chemical composition and physical form, making identification the necessary first step. Fertilizers are broadly categorized into organic and synthetic (inorganic) types, with synthetic versions typically composed of nitrogen, phosphorus, and potassium compounds. Organic fertilizers, derived from natural sources like manure or plant matter, generally pose a lower environmental risk.
A more critical distinction is whether the product contains additional pest-control chemicals, such as herbicides or insecticides. Products often labeled as “weed and feed” or “plus 2” are considered composite chemicals because they combine nutrients with pesticides. these combination products must be treated as hazardous waste due to the toxicity of the added chemicals.
Always check the product label for active ingredients and any warning symbols like “Poison,” “Caution,” or “Warning”. If the fertilizer is a liquid or a powder mixed with a pesticide, it is automatically elevated to a higher-risk category for disposal. The percentage of nutrients, indicated by the N-P-K numbers on the packaging (e.g., 10-8-6), helps classify the product but does not determine its hazardous status.
Safe Methods for Reducing and Reusing Product
Before resorting to formal disposal, it is always preferable to use up or re-home any viable fertilizer to keep it out of the waste stream. Most fertilizers, when stored correctly in a cool, dry place, can remain effective for a very long time, even if they have slightly solidified. If a granular product has clumped, it can often be broken up or dissolved in water for a thin, even application across a lawn or garden area at the recommended rate.
Liquid fertilizers that have separated or become old can still be used if carefully diluted with water and applied to plants. Applying the product sparingly, rather than doubling the rate to use it up quickly, prevents nutrient burn and excessive chemical runoff. An alternative is to offer the product to neighbors, local community gardens, or non-profit organizations that may have a use for it.
If you must store the product until it can be used or disposed of, keep it in its original, sealed container to maintain the integrity of the label and prevent accidental spills. Never mix different types of fertilizers together, as this can lead to unpredictable and potentially dangerous chemical reactions. For liquid products, placing the container inside a plastic bag can provide an extra layer of protection against leaks during temporary storage.
Formal Disposal Through Collection Programs
When fertilizer cannot be safely reused, it must be discarded through formal collection programs. Most synthetic fertilizers, especially liquids and any product containing herbicides or pesticides, are designated as Household Hazardous Waste (HHW). This classification means they cannot be placed in regular trash or recycling bins, as they pose a risk to sanitation workers and landfill environments.
The responsibility for collecting HHW rests with local municipalities or county waste management authorities. Contact your local government’s waste department or check their website for information on permanent HHW drop-off facilities. Many communities also host periodic collection events where residents can bring hazardous materials for disposal. These programs ensure that the materials are handled by professionals and sent to specialized facilities for treatment or incineration.
Preparation for drop-off requires keeping the fertilizer in its original container so facility staff can identify the contents. If the original container is damaged, transfer the contents to a clearly labeled, sealed, non-leaking container. Transport the items securely, such as by placing them in the trunk of a vehicle, to prevent spills during the drive. Because regulations and accepted materials vary widely by location, confirming the details with the local HHW program before traveling ensures proper, compliant disposal.