The volume of organic material generated by lawn maintenance presents a significant challenge for waste management nationwide. Homeowners produce millions of tons of yard trimmings annually, which the EPA estimated at 35.4 million tons in 2018. Comprising over 12% of the municipal solid waste stream, grass clippings are a nutrient-rich resource. They can be managed effectively to reduce landfill strain and benefit the home landscape.
Grasscycling: Leaving Clippings on the Lawn
The simplest method for handling grass clippings is grasscycling: leaving them directly on the turf. This technique transforms the clippings into a natural, slow-release fertilizer. Clippings are composed of 80 to 90 percent water, meaning they decompose rapidly, typically vanishing within two weeks.
This decomposition returns nutrients, most notably nitrogen, directly to the soil. Grasscycling can supply 25 to 50 percent of a lawn’s total nitrogen needs, significantly reducing the requirement for supplemental fertilizer. To ensure clippings decompose quickly without smothering the turf, follow the “one-third rule.” This rule states that no more than one-third of the grass blade’s total height should be removed during a single mowing session.
Mowing frequently ensures the clippings are small enough to filter down to the soil surface for microbial breakdown. Utilizing a mulching mower or specialized mulching blade chops the material into fine particles that disappear faster. These small pieces do not contribute to thatch buildup, which is primarily caused by slowly decomposing stems and roots.
Transforming Clippings into Compost
When the volume of clippings is too great for the lawn, they are a valuable component in a home composting system. Grass is a “green” material, high in nitrogen, which is necessary for the microorganisms driving decomposition. Fresh grass clippings have a low carbon-to-nitrogen (C:N) ratio, typically ranging from 12:1 to 25:1.
For optimal composting speed and efficiency, the total mixture must achieve a C:N ratio of approximately 30:1. Nitrogen-rich clippings must be balanced with high-carbon “brown” materials, such as dry leaves, shredded paper, or straw. Piling wet clippings alone creates a dense layer that excludes oxygen, leading to undesirable anaerobic decomposition.
This anaerobic process generates foul odors, particularly ammonia and sulfurous compounds, and significantly slows the composting cycle. To avoid this, clippings should be mixed or layered with brown materials to prevent compaction and maintain airflow. A common guideline is to use roughly two parts of dry, brown material to one part of fresh, green clippings by weight or volume.
Immediate Use as Garden Mulch
Grass clippings can be immediately repurposed as a temporary mulch layer in gardens or flower beds to suppress weeds and conserve soil moisture. Applying this organic cover helps moderate soil temperature, keeping the root zone cooler during summer. As the clippings slowly break down, they provide a gentle, steady source of nitrogen to surrounding plants.
The application technique is crucial to prevent issues similar to those in improperly managed compost. Clippings must be spread in a thin layer, ideally no more than one to two inches deep. A thicker layer will cause the wet material to mat together, forming a barrier that prevents water and air from reaching the soil. This matting promotes mold growth and anaerobic conditions, leading to unpleasant odor.
It is best to allow fresh clippings to dry slightly before application or apply them in multiple thin layers over several days. When mulching, keep the material several inches away from the stems and crowns of garden plants. Direct contact with moist clippings holds too much water against the plant tissue, which encourages rot and harbors pests.
Municipal and Landfill Disposal Options
While reuse is the preferred practice, disposal is sometimes necessary, such as when a lawn is diseased or chemically treated. Homeowners must then rely on municipal collection services or local drop-off centers. Many state and local regulations discourage or ban yard waste from being placed in traditional municipal solid waste landfills.
These regulations exist because highly organic yard trimmings constitute a large portion of landfill waste. In 2018, approximately 10.5 million tons of yard trimmings were still sent to landfills, consuming valuable space. Collected yard waste is typically directed to a separate facility for large-scale composting or mulching operations. Homeowners must adhere to local rules, which often specify the use of compostable paper bags or reusable containers for curbside collection, and may limit the volume collected.