By Allison Edwards MS, RDN
What is composting?
Composting turns organic matter, such as leaves and food scraps, into fertilizer for the soil. Everything that grows will break down in time, and composting just speeds up the process by making ideal conditions for bacteria, fungi, and other decomposing organisms. The finished matter looks like fertile garden soil and is called compost. Gardeners and farmers often call this “black gold,” because it is rich in nutrients & can be used for agriculture.
Benefits of Composting
Reduce waste: Composting is a great way to recycle organic waste at home. Food scraps and garden waste make up about 28% of what we throw away. 267 million tons of public waste was made in 2017 in the U.S. ⅔ of that was sent to landfills and incinerators. Not only is this bad for the environment, we also spend billions of dollars on waste management.
Cut methane emissions: Normally, organic matter goes through aerobic decomposition when it is breaking down. When compostable waste goes to a landfill, it gets buried under trash and goes through anaerobic decomposition instead. During anaerobic decomposition, bio-gas is created as a by-product and is about 50% methane and 50% carbon dioxide- both of which are greenhouse gases.
Conserve water: The water-retaining capacity of soil grows when compost is added. Each 1% increase in compost helps the soil hold 20,000 gallons more water per acre than soil without any compost. Compost makes the soil healthier, which allows farmers to reduce the amount of water they must use on crops. It also creates higher yields than farming on degraded soil.
Uses for compost
Use as mulch, place on lawns, and add to potted plants, crops, garden beds, or around fruit trees. Compost does not go bad but can become too dry or too wet. The older it is, the more nutrients may be lost!
Types of composting
Trench- organic waste is buried in the soil about 12-24” deep and is then left to compost. It is invisible and has no odor because it is buried. This is best for a single use of organic matter and would not be useful if you want to compost daily.
Bin
Closed bin- an enclosed structure is used to hold compost and retains heat and moisture. It often has an open bottom. Organic materials can be added to it daily. The pile needs to be turned about once per week.
Open bin- can be simple as a loop of chicken wire that you dump into, or just pile on the ground without an enclosure. Organic materials can be added to it daily. The pile needs to be turned about once per week.
Tumber- sealed container (with ventilation) that is fixed on an axle or base and can be turned with a handle. Organic materials can be added to it daily. It should be turned about twice per week.
Vermicomposting- this is also known as “worm composting,” because organic matter is added to bins with live worms that produce natural and odorless castings (fertilizer) in 3-6 months. Essentially, the worms live in the compost bin, eat, and digest the compostable material. This can be done indoors or outdoors, year-round and requires very little upkeep other than harvesting the compost every few months.
What to compost and what not to compost
Compostable materials can be divided into two categories: nitrogen-rich (“green”) and carbon-rich (“brown”). Green materials include vegetables, fruits, table scraps (no meat/dairy), fresh grass, coffee grounds and filters, flowers, tea leaves, seaweed, and fresh leaves. Brown materials include dry leaves, shredded paper, shredded cardboard, wood chips or mulch, sticks, straw, hay, newspaper, eggshells, and shredded paper bags. There needs to be a equal balance between green and brown sources.
Some items are not compostable or should not be composted for a variety of reasons. Items that should not be composted include meat or fish, dairy products, bones, animal feces or litter, shiny/coated paper or cardboard, plastic, stickers on fruit peels, coal, ash, fat/grease/oils, plants treated with pesticides, weeds that have gone to seed, diseased or insect infested plants, and black walnut tree leaves.
How to know your compost is ready
Most compost takes ~2 months to finish. You can tell that it is ready to use when it has an earthy smell, consistent texture and is dark brown. It will look like dark soil. Be sure to save a small amount of finished compost to start new compost with to speed up the process!
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