Home Composting
A guide for composting yard and food waste
Link to the official
Massachusetts DEP Composting website
The Commonwealth of Massachusetts
Executive Office of Environmental Affairs
Department of Environmental Protection
Contact: Ann McGovern, 617-292-5834
City of Cambridge
Department of Public Works
Recycling Division
Contact: Randi Mail, 617-349-4866
Cambridge Recycling, Inc.
Contact: Robert Winters, 617-661-9230

What is composting?
Composting is a controlled process of decomposition of organic material. Naturally occurring soil organisms recycle nitrogen, potash, phosphorus, and other plant nutrients as they convert the material into humus.

Actually, the word compost derives from the word composite. It is the deliberate mixture of various materials that distinguishes composting from ordinary decomposition of organic materials. The finished product of composting is humus (the organic part of soil). Any given soil sample consist of many things, including humus, sand, alluvium, clay, stone dust, and much more. In North Cambridge, soils tend to be rich in clay. In other parts of Cambridge, higher than desirable levels of lead can be found in the soil - the remnants of insecticides, leaded paint, and leaded gasoline.

Generally, the humus derived from a well-balanced compost pile is more beneficial than ordinary humus. The leafy materials tend to provide excellent absorbency for water and air, and the food wastes and other high nitrogen materials make for an excellent fertilizer. Humus derived exclusively from leaves tends to provide absorbency and aeration but must be supplemented with additional fertilizers if used in the garden. Humus derived exclusively from food wastes is very rich in nutrients but usually lacks sufficient body.

Benefits of Composting
Composting is a convenient, beneficial, and inexpensive way to handle your organic waste and help the environment. Composting:

What should you compost?
Yard wastes such as leaves, grass clippings, and weeds make excellent compost. Fruit and vegetable scraps, plus food wastes such as coffee grounds, tea bags, and egg shells can be composted. To keep animals and odors out of your pile, do not add meat, bones, fatty food wastes (such as cheese, grease, and oils), dog and cat litter, and diseased plants. Do not add invasive weeds and weeds that have gone to seed to the pile.

Other materials that are OK: Stuff that goes bad in the fridge, paper towels and egg cartons (soak in water and pulp them for best results), and very small amounts of otherwise prohibited food wastes.

A System for Backyard Composting
A good system consists of a kitchen container (for storage of materials bound for the compost pile), an animal-proof and rodent-resistant composter located conveniently outside the house, a pitchfork or other tools for aerating the most active parts of the compost pile and burying in new materials, and a screening device for harvesting the humus from your pile (a milk crate with openings of an inch or less works quite well and even has handles). A leaf shredder is handy in the fall, and is best shared among neighbors. For a list of neighbors who have purchased composters from us, contact Robert Winters at 661-9230. You can split the cost and use the money saved for a block party.

Elements of a Good Compost Pile
With these principals in mind, you can convert your organic wastes into resources by turning your spoils to soil.

The Biodegraders
Nature has provides an army of workers who specialize in decomposing organic material. These "critters" - bacteria, fungi, molds, earthworms, insects, and other soil organisms - eat all types of organic material and in the process convert nutrients into a form plants can utilize. Without those compost critters, we would be surrounded by mountains of leaves and the soil would be barren. The process of composting is simply a matter of providing the soil organisms with food, water, and oxygen. They do the rest.

Organic Material
Organic material contains varying amounts of carbon and nitrogen which nourish the organisms naturally present in your compost pile. (Billions of bacteria inhabit the surface of every leaf and blade of grass in your yard.) The critters need both carbon and nitrogen. An easy way to provide both of these is to remember that brown, woody materials, such as autumn leaves, are high in carbon while green, moist materials, such as grass clippings, are high in nitrogen (refer to the table below).

Alternating layers of brown and green materials will yield finished compost in three to eight months. Leaves alone break down in six to fifteen months. Grass clippings or food scraps composted alone result in unpleasant odors because they contain more nitrogen than the compost organisms can use. Layer leaves or straw with green material, or let it dry until it turns brown before composting it alone.

The compost critters need oxygen, just as we do. Lack of oxygen will slow down the composting process and cause odors. Turn your pile, fluff it with a hoe or compost turning tool, or build air passages into the pile with cornstalks to provide oxygen to the organisms.

Compost organisms need a moist environment. The pile should be as damp as a wrung-out sponge, but not dripping wet. Make sure leaves are damp when you add them to the compost pile because they will not break down if they are dry. Since moisture evaporates as the pile heats up (a sign of active composting), let rain and snow replace it, or add water during dry spells. A cover helps retain moisture in hot weather.

The short rap:
Composition - Too much brown will slow it down, too much green will cause a scene.
Balance leaves and other carbon-rich materials with food waste, grass clippings, and other nitrogen-rich materials. A pile with too much nitrogen-rich materials can become anaerobic and smell like ammonia or worse. Pile temperatures can rise so high that beneficial microbes are killed. Ideal composting temperatures range from about 95 to 130 degrees Fahrenheit.

Moisture - Too dry and the microbes die, too wet and they suffocate.
Air can't penetrate a soggy pile and stinky sludge may result - a sewer-like odor.

Air - Let your nose be your guide.
A warm or hot pile is ideal, but it will consume oxygen faster. Aeration will assist the microbes, but don't overdo it or you'll reduce the temperature too much. Ammonia-like odors (too much nitrogen) or sewer-like odors (too much moisture) mean that it's time to aerate. A good compost pile will have a sweet smell reminiscent of alfalfa or rich, musty soil. Bad odors mean something is not right.

How to Use Compost
When the composted materials look like rich, brown soil, it is ready to use. Apply one-half to three inches of finished compost and mix it in with the top four inches of soil about one month before planting. Compost can be applied as a top dressing in the garden throughout the summer. Compost is excellent for reseeding lawns, and it can be spread one-quarter inch deep over the entire lawn to rejuvenate the turf. To make potting soil, mix equal parts compost, sand, and loam. You may put the compost through a sieve to remove large particles - these can go back in the pile.

Milk crates are handy for harvesting compost, if you can find one with a grid between one-half and one inch on a side. A screening device with too small a grid requires much more effort and provides little additional benefit. Consider spreading your unscreened compost out in the sun to dry a bit and allow any worms to retreat into the ground.

If you would like additional leaf compost, it is available free at the Recycling Center in the DPW Yard during the warm weather months. The quality varies depending on its source, but it's all pretty good. Additional screening is sometimes necessary to remove rocks, large pieces of wood, and debris.

Grass clippings, leaves, and woody yard wastes can be used as mulch in gardens and around shrubs to keep the soil moist, control weed growth, and add nutrients. Woody materials should be chipped or shredded. Use a mulch of pine needles around acid-loving plants. Leaves will work first as mulch, then as a soil enricher as they decompose. Grass clippings should be dried before using as a mulch. Do not mulch with grass clippings which have been treated with herbicides; composting them first, however, will break down the herbicides.

Wood chip also makes for excellent weed-free, all-natural garden paths. Replenish as needed. Wood chip from the pruning of Cambridge street trees is available for free during the warm weather months in the DPW Yard during the hours that the Recycling Center is open.

Mulching with almost finished compost can help to prevent disease in plants.

Composting Without a Yard
Composting can be done indoors using an earthworm farm. Not only can you recycle your food scraps, you can also have a steady supply of fishing bait! (Actually, composting worms are not the best choice for bait.) For more information, call DEP's Solid Waste Management Program.

Composting Bins
Animal-Proof, Rodent-Resistant Compost bins

Several models are were available through the City of Cambridge. They are were:

Composter Dimensions Volume Features Price
Earth Machine(EM) 30 inch diameter at base, 24 inch diameter at top, 32 inch height. 11 cubic feet (approx.) Circular design (tapered). Door at base for removing finished compost. 18 inch opening at top. Comes with bottom screen. $16.00
no longer available
28 inch by 28 inch square base, 24 inch by 24 inch square top, 32 inch height 12 cubic feet (approx.) Square design. Two doors at base. Top opening is very wide for manipulating the pile. Bottom screen available by special order. may be purchased at Pemberton Farms ($60?)
Brave New Composter
Variable diameter up to 43 inches. 30 inch height. Up to 24 cubic feet, adjustable. Circular design with inverted cones for top and bottom, rope handle. Large volume is ideal for large leaf piles and community gardens. No doors.
[This model is available only on request.]
No longer available
Aeration tool (T) Arrowhead shaped tool to be attached to any light-duty wooden mop handle. Used for mixing materials in the compost pile, distributing moisture, and aeration. Tool is especially useful for composters with a narrow opening on top. $1.00
no longer available, but we could try to locate some if there's demand

Other composters and composting equipment may become available. We will try to supply other equipment on request, if costs can be contained and if there is sufficient demand. Call Robert Winters of Cambridge Recycling at (617)-661-9230 or send e-mail to Robert@rwinters.com.

Holding Bins
These portable containers are the simplest way to compost. Turning is optional.

Turning bins
A series of three or more bins allows you to make compost in a short time by turning the materials on a regular schedule.

This is an excellent option for large community gardens. The Broadway and Boardman Garden provides an excellent example of this system. The Sacramento St. Garden also utilizes this system. You can also marvel at Compost King of Avon Hill John Matthews' five-bin system at 63 Avon Hill St.

Earthworm Bin
This is an excellent alternative for apartment-dwellers and office buildings. It is also a good idea for the cold winter months. For more information or to purchase redworms (red wigglers), contact David Lovler at (413)-549-4456.

How To Make a Compost Pile
There are as many different ways to make compost as there are people who do it. The following guidelines will get you started, but soon your own experience will help you tailor a method that best fits your needs.

Build or purchase a compost bin. Check to see if your community has a composting bin distribution program, or order from a garden catalogue, nursery, or hardware store. Enclosed compost piles keep out pests, hold heat and moisture in, and have a neat appearance. Or, bins can be made of wire, wood, pallets, concrete blocks, even garbage cans with drainage holes drilled in them. In urban areas, rodent-resistant compost bins - having a secure cover and floor and openings no wider than one-half inch - must be used.

Set up the bin in a convenient, shady area with good drainage. A pile that is about three feet square and three feet high will help maintain the heat generated by the composting organisms throughout the winter. Although a smaller pile may not retain heat, it will compost.

Start the pile with a layer of course material such as corn stalks to build in air passages. Add alternating layers of "brown" and "green" materials with a shovelful of soil on top of each layer. Then mix the layers. Shredding leaves or running over them with a lawn mower will shorten the composting time. Be sure to bury food scraps in the center of the pile.

Add water as you build the pile if the materials are dry.

As time goes on, keep oxygen available to the compost critters by fluffing the pile with a pitchfork or compost turning tool each time you add material. A complete turning of the pile - so the top becomes the bottom - in spring and fall should result in finished compost within a year. More frequent turning will shorten the composting time.

High Nitrogen "Green" Ingredients High Carbon "Brown" Ingredients
alfalfa hay/meal autumn leaves
grass clippings cornstalks
blood meal straw
manure (cow, horse, chicken, rabbit) pine needles
food wastes (fruit and vegetables,
   coffee grounds, tea bags, egg shells)
wood chips
Seaweed sawdust

Where to get more information
In cooperation with the Massachusetts DEP, the State of Connecticut has produced a video entitled Turning Your Spoils to Soils, which is available in most local libraries in Massachusetts. DEPís Solid Waste Management Program also provides technical assistance and reference materials on composting, and can be reached at 617-292-5834.

Locally in Cambridge, call:
Recycling Division of the Cambridge Department of Public Works (617-349-4866); or 
Robert Winters of Cambridge Recycling, Inc. (617-661-9230).

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