Ask A Scientist
How long does it take for most garbage to decay and can it be used for fertilizer?
Asked by: Shawneh Swan
School: Chenango Valley High School
Career Interest: N/A
Answer from Juliet Berling
Environmental Resource Manager and Adjunct Profess
Research area: Environmental Policy and Planning, Sustainable Living, Recycling and Solid Waste Management PhD school: Texas A&M University, College of Architecture Interests/hobbies: Reading, gardening, chasing after kids Family: Husband Jeff, sons Ian 11, 5th Grade Thomas Jefferson Odyssey of the Mind World Champion; Jeff Jr. 7, 1st Grade Thomas Jefferson; John David, 4 Pre-kindergarten, St. Thomas Aquinas; and daughter Anne Elizabeth 9, 3rd Grade Thomas Jefferson. Web page
Garbage that is placed in a landfill can take a long time to decompose, if it ever does. A landfill is designed to keep air and water out - two things needed for decomposition. A landfill is built into or on top of the ground. Trash is separated from the environment (groundwater, air, rain) by a liner and daily covering of soil. Under these conditions, trash will not decompose much. A landfill is not like a compost pile, where the purpose is to speed up decomposition.
Trash put in a landfill will stay there for a very long time. In fact, when old landfills have been excavated or sampled, 40-year-old newspapers have been found with easily readable print. Landfills are not designed to break down trash, merely to bury it. When a landfill closes, the site, especially the groundwater, must be monitored and maintained for up to 30 years!
Garbage in a landfill does not make a good fertilizer. Now, garbage that has been composted is another thing entirely! In order for organic material – fruit, vegetables, kitchen scraps, etc. to decompose they need to be in an oxygen rich environment complete with heat and water. Composting is a process by which organic material is broken down by microorganisms in the presence of oxygen. The microorganisms break the material down through aerobic respiration. The microorganisms also require water. Through the respiration process, the microorganisms give off carbon dioxide and heat -- temperatures within compost piles can rise as high as 100 to 150 degrees Fahrenheit (28 to 66 C). If the compost pile or bin is actively managed by turning and watering it regularly, the process of decomposing into finished compost can happen in as little as two to three weeks (otherwise, it may take months). It can be done inexpensively by every household and produces a product -- finished compost or humus -- that can benefit the environment as a natural fertilizer for gardening and farming.