Public Health and Environment
Backyard Composting
What is it?
Composting is a biological process in which organic material such as fruits, vegetables, leaves, and plant trimmings are converted into a soil like material called humus. During this process, thousands of bacteria, insects, and fungi feed on, break down, and digest the organic matter leaving behind rich dark humus, also called finished compost. The speed at which the composting process occurs depends on the amount of air, moisture, and type of materials in the pile or bin.
For more information on getting your own compost bin or pile started, what to add to your compost pile, or how to speed up the process please see the "How To Get Started," "What To Add," and "How Long Does It Take."
Why Do It, What Are the Benefits?
Composting is an easy way for you to help the environment. By composting, you recycle organic materials, save valuable resources, and reduce the burden on our waste disposal system. Composting can also save you money by reducing the weight and volume of your discarded waste possibly reducing garbage bills. Keeping organic materials out of your trash can or cart also helps reduce odors, especially, during warm weather.
Finished compost, or humus, is a great soil conditioner. Adding finished compost to your lawns, gardens, and flower beds can help them retain moisture, while reducing the need and frequency of watering. Working compost into clay type or "tight" soils can improve soil structure and drainage, and permit better and deeper root penetration. The naturally occurring microorganisms of the compost have also been shown to be beneficial to maintaining plant health.
How To Get Started
I want to start composting on my own but how does it work?
Composting takes place around us all the time. As a natural process, composting is happening in every landscape, including your residential yard or garden. In a pile or bin, we are bringing the process into a more controlled environment, supplying it with ample food, moisture, and air to speed it up and capture the finished product, humus.
So do I need a bin to start composting?
A compost bin is not needed to be a successful composter. Composting can be, and often is, done in open heaps or piles, but in an urban setting, bins are often preferred. The use of a bin may be also be required by local ordinances and bins help to keep piles neat and visibly pleasing. Enclosed composting bins also help keep pests away, and aid in moisture and heat retention, thereby, speeding up the process.
Where to Place Bins
The location of a compost bin affects the length of time it takes your pile to decompose. A few suggestions when deciding where to place your bin:
- Easily accessible part of the yard
- Where it is level and the soil is well drained
- Near a wind break to protect from drying winds and intense sunlight
- Away from wood structures that may rot
- In an area that won't offend neighbors
Types of Bins
Bins can be constructed of wood, wire, brick or plastic. See the web sites listed below for more detailed descriptions on bin types and construction.
 Pierce County, Washington
If you choose to build your own bin, this website may help you with the construction. The website provides great instructions for building compost and worm bins.
University of Minnesota Extension Service
This site explains why you need a structure and shows how to build your own bin.
Composters.com
Bins can also be purchased. This site provides a directory of some products and accessories available for purchase.
Composters.net
This website provides a rating chart for build your own bins, stationary units, and tumbling and rolling units.
What To Add
Green Material - Anything that is fresh, wet, or the color green.
The following is a partial list of "Greens." There are thousands of other green materials readily available for composting.
- fruit rinds
- vegetable peels
- egg shells
- coffee grounds and filters
- tea bags
Lawn & Garden Waste
- fresh green grass clippings
- manures
- weeds*
- old plants
- milfoil
- seaweed
- hair
Brown Material - Brown materials can be thought of as things that are dry, old, or the color brown.
In the Fall, some avid composters will stockpile brown materials so that it can be combined with food waste during the Winter and the plentiful greens of Spring and Summer. Compost bins can also be used to destroy confidential paper such as cancelled checks, bills, and credit applications; just be sure the ink is vegetable based or biodegradable. These paper items are a great carbon source and are in the brown-carbon rich material category. Other brown materials include:
- dead dry leaves
- brush
- twigs
- wood chips
- saw dust
- hay
- straw
- newspaper
- paper napkins
- towels
- tubes
Do Not Add
- meats
- fatty foods
- bones
- fish
- dairy products
- human and pet wastes
- diseased weeds
Carbon/Nitrogen Ratios
Carbon and nitrogen are the essential elements of a compost pile. Carbon provides energy. Carbon-rich materials are referred to as "browns." Nitrogen is a source of protein. Nitrogen-rich materials are commonly called "greens." A carbon to nitrogen ratio of 30:1 is ideal for backyard compost bins or piles. The carbon to nitrogen ratio of some common materials are listed below.
- 10:1 humus
- 15:1 vegetable wastes
- 19:1 grass clippings
- 20:1 weeds, coffee grounds, rotted manure
- 40:1 fruit wastes
Browns
- 60:1 dry brown leaves, corn stalks
- 90:1 straw
- 170:1 newspaper
- 500:1 sawdust
- 700:1 wood chips/twigs
The Question of Lime
Unless your pile contains large amounts of acidic material such as pine needles or citrus fruit wastes, it is unnecessary to add lime. Finished compost is slightly alkaline and adding lime will only increase the alkalinity. If excessive amounts of lime are added to compost, the pile may loose valuable amounts of nitrogen. A very light application of lime to your pile can temporarily solve odor problems.
How To Build A Pile
Compost piles can be built two different ways. The first is the build-as-you-go method. To do this, simply add to the pile as waste is available. Be sure to maintain a moisture level equal of that of a wrung out sponge. This method will take longer to yield finished compost, about 6 to 12 months, but the more attention you give to your composting operation, the quicker the process will be.
A faster method of pile construction is layering or building a pile by layers one on top of another. In a layered pile, the bottom layer should consist of coarser materials such as twigs, wood chips or corn stalks; this will help aid in aeration of the pile. The next layer should consist of green material, and then simply continue alternating brown and greens until the bin is full. Be sure to moisten each layer as it is added and build layers 3 to 6 inches high. Layering should yield finished compost within 1 to 3 months. Adding a nitrogen rich "activator" may speed up the process, turning the pile every week will aerate it, allowing the decomposing microbes to work faster.
How Long Does It Take?
The length of time that it takes your pile to decompose, and for it to be ready to use, depends on the following five factors:
1. Aeration
It is necessary to turn the pile every couple of weeks to circulate oxygen so that aerobic microbes can continue to break down the organic material.
2. Moisture Level
An adequate moisture level (as wet as a wrung out sponge) is necessary to provide optimum conditions for composting.
3. Carbon/Nitrogen Ratio
An ideal ratio of 30:1 will aid in faster breakdown and compost will be available sooner. This carbon and nitrogen balance generates high temperatures that slowly cool, speeding up decomposition.
4. Size of Ingredients
Large materials should be shredded, and all twigs and branches should be chipped. This provides a greater surface area so more microbes can work on it at the same time.
5. Temperature of Heap
Compost piles can reach temperatures of 160 degrees F. High temperatures are needed to destroy disease, germs and seeds from weeds. High temperatures produce humic acid, which permits plants to absorb the nutrients in the compost.
Uses of Finished Compost
Compost is ready to be used when the heap has decomposed to nearly half its starting size and there are few identifiable particles. Finished compost should be dark brown and crumbly with a pleasant earthy smell. You may also use partially decomposed material for mulch. Mulch has similar uses as compost, but is heavier and less flaky. The main purpose of compost is to improve soil and plant health, whereas mulch retains moisture and maintains soil temperature.
Uses for your finished compost or mulch:
- Dig about three inches into soil before planting.
- Apply about two inches to lawns, spread and rake in.
- Dig it in around plants and shrubs.
- Mix it into potting soil for house plants.
- Use as a top dressing around trees, flowers, and shrubs.
- Till into gardens when planting vegetables, flowers...
Compost Tea
The making, use, and benefits of compost tea is a new area that has experienced considerable growth and research in the few years. In general, compost tea is made by steeping finished compost in water which is then applied on plants and is believed to enhance their growth. One theory on this process is that the microorganisms living in the compost are dispersed in the liquid solution and then spread onto the receiving plants and soil where they act as a natural booster assisting the plants in combating pathogens.
Problems & Solutions
| Problem |
Cause |
Solution |
|
Ammonia
Odor |
Too much green material. |
Turn pile and add browns, carbons. |
|
Rotten
Odor |
Too wet, creating anaerobic conditions. |
Turn pile, add dry carbon material. |
| Flies |
Attracted to food waste. |
Bury food in center of pile and cover with
brown materials. |
| Rodents |
Attracted to meats and fatty foods. |
Do not add meats, fats, or dairy, turn pile,
and put a lid on bin. |
| Pile
isn't hot enough (<90o F) |
Pile too small, not enough oxygen, too many
browns or cold weather. |
Make pile larger, turn pile, add green
material, add extra layers to insulate. |
| Pile
is too hot (>150o F) |
Pile is too large, insufficient aeration, too
much nitrogen. |
Turn pile, make a smaller pile or add brown
material. |
| Pile
is too wet |
Too much green, not enough air. |
Add carbon material and turn pile. |
| Pile
is too dry |
Not enough moisture. |
Add green nitrogen materials, or add water
but don't saturate the pile. |
|
