Material For Composting

Materials For Composting

            It is possible to make compost with almost any kind of organic material, including straw, hay, wood chips, sawdust, and non-meat food wastes from restaurants.  However, home compost systems usually use the yard waste materials normally produced by caring for of the average home landscape--leaves, grass clippings, weeds, plant trimmings, sod, and non-meat kitchen waste.  No matter what material is used in composting, it will contribute some basic nutrients to the composting equation in the form of nitrogen (N), phosphorous (P), and potassium (K), the three primary plant nutrients.  Much of the nitrogen is going to be consumed by the decomposition process, but much of the phosphorous and potassium will end up in some form in the final product, the finished compost. 


            The NPK ratings of composting materials are useful only to illustrate for you the relative value of each of the materials that you may use in your particular pile.  Home composters do not need to worry about mixing various materials to achieve any kind of NPK balance in the final product. Such fine tuning is not possible in any kind of precise manner. Monitoring nutrient balances in compost is best left to commercial composting systems, and often, even at that level, the compost is usually made of whatever material happens to be available.  As each composting material is discussed below, the approximate NPK value of that material will be noted, just for comparison to other materials.  Remember, materials high in nitrogen will need to mixed with a higher proportion of materials high in carbon and vice versa to maintain an optimum carbon/nitrogen ratio for efficient decomposition in the pile. 


Common Composting Materials

            In this section we'll review the relative merits of those materials most commonly available for composting over most of North America. Then some other materials that may be available in certain parts of the country will be reviewed. 


List of Common Household Materials That Can be Composted

Grass, leaves, weeds, vegetable peelings, fruit rinds, coffee grounds, chunks of turf, vines, grass clippings, tea bags, paper towels, egg shells, corn husks, peanut shells, corn cobs, twigs, shredded branches, bark, pine cones.


Grass clippings

            Grass clippings make up the largest portion of the average volume of yard waste produced by American homes.  As we pointed out in Chapter ###, it is best, in most cases, to leave grass clippings right on the lawn as it is mowed so they can feed and revitalize the grass plants directly.  In those instances when you do feel you must collect your grass clippings, make use of them as a thin mulch around plants in the yard.  In the end, however, there may be situations where it is expedient to put grass clippings into the compost pile.  Grass clippings are good for composting ONLY if they are mixed with leaves or some other carbon or dry material such as straw, hay, sawdust or even Canadian sphagnum peat moss purchased from the local garden center.  If grass clippings alone are piled in a compost bin, the pile will rapidly become anaerobic (without oxygen) and begin to smell terribly. 


[Photo - A line of bags of grass clippings sitting on the curb waiting for municipal trash pickup]


   NPK Percentage Value of Grass Clippings In Compost

                        Nitrogen            Phosphorous            Potassium

Green clippings  0.66                          0.19                          0.71

Dried Clippings  1.20                          0.40                          1.55


            Some home composters take advantage of their neighbors' bad habits and collect bags of grass clippings from around the neighborhood to add valuable nitrogen to the compost pile.  In those cases where large amounts of grass clippings are available for composting, take time to dry them first.  Spread the freshly cut grass over a paved driveway or similar surface to bake in the sun for at least a day.  When it dries and begins to turn pale and strawlike, the grass can be dumped in a compost bin without danger of its putrefying and smelling bad. 


            Another concern with grass clippings is whether there are any residues of herbicides or other pesticides on the clippings when they are introduced into the compost bin.  The best way to be sure the clippings are safe, if they are not from your lawn, is to accept only clippings that are collected after a fairly heavy rain.  A steady rain will wash any dangerous pesticide residues from the blades and down into the soil. 



            For homeowners with deciduous trees, leaves represent a large percentage of the total yard waste produced by that landscape.  As was noted in Chapter ##, chopped leaves make a marvelous mulch and we recommend that you use as many of the leaves accumulated in the fall for that purpose as is practical.  Then, after all the mulching has been done, the remaining chopped leaves will make a excellent carbon rich material for the compost pile or bin. 


[Photo - Someone raking leaves in the fall]


               NPK Percentage Value of Leaves In Compost

                        Nitrogen             Phosphorous            Potassium            pH

Red Maple            0.52                        0.09                        0.04                        4.7

Sugar Maple            0.67                        0.11                        0.75                        4.3

American Beech 0.67                        0.10                        0.65                        5.1

White Ash            0.63                        0.15                        0.54                        6.8

White Oak            0.65                        0.13                        0.52                        4.4

East. Hemlock 1.05                        0.07                        0.27                        5.5

Balsam Fir            1.25                        0.09                        0.12                        5.5


            We noted earlier that leaves will compost more quickly if they are chopped or shredded before being piled into a bin.  Whole leaves will decompose in time, but they take up more space and almost twice the time chopped leaves do to turn into finished compost.  Any kind of leaves can be composted.  All leaves, no matter whether they are acidic or alkaline when they start out, will decompose into compost that has an almost neutral pH (6.8 to 7.2).  While pine needles, oak leaves and coffee grounds are naturally acidic and make ideal mulch for acid-loving plants such as blueberry, azalea, rhododendron, or for inclusion into soil that tends to be alkaline, composting makes them essentially neutral in pH.


            Pine Needles

            Homeowners who have many pine trees on their property will have a supply of pine needles rather than leaves to deal with.  Pine needles are an excellent material for mulching acid-loving plants such as azalea and rhododendron.  If there are some extra pine needles, they can be composted, however they will take somewhat longer than leaves to fully decompose.  Pine needles have a thick outer coating of a waxy substance called cutin that is slow to break down.  Shredding pine needles will help speed their decomposition.


   NPK Percentage Value of Pine Needles In Compost

Nitrogen             Phosphorous            Potassium            pH

 0.46                          0.12                          0.03                        ?


[Photo - Pine needles accumulating under a pine tree(s)]



            Weeds are all those plants that we, as homeowners with a landscape to maintain, decide are not wanted in our particular ecosystem.  Someone's flower Queen Anne's lace is another person's weed.  With only a few exceptions, most annual and perennial weeds will compost easily, although the same rules apply as with grass clippings.  Large amounts of freshly pulled green weeds represent an overload of nitrogen rich material that can settle into a tight anaerobic mass that smells pretty bad.  Also, the more fibrous weeds such as Canadian thistle will compost more quickly if they are shredded.  Mix fresh weeds with some dry material such as chopped leaves to forestall the possibility of odor.  People living in the south have two excellent candidates for compost.  They are kudzu and the ubiquitous water hyacinth, both rampant throughout the south. 


   NPK Percentage Value of Some Weeds In Compost

                        Nitrogen             Phosphorous            Potassium

Ragweed              0.76                          0.26                          n/a

Crabgrass              0.66                          0.19                          0.71

Pigweed              0.60                          0.16                          n/a


            The concern with some weeds is that they may spread seeds or roots to the rest of the landscape when the finished compost has been spread around.  That happens when the compost is made using the passive technique in which there is not the high temperatures (140 to 160 F) achieved that will kill most weed seeds and roots.  If you compost lots of weeds, then you might want to choose the active composting method to be sure weed seeds are destroyed in the process.  To avoid potential problems discard invasive weeds such as quack grass, morning glory, and buttercup in the trash. 


            Kitchen Garbage

            The average American household produces over 200 pounds of kitchen waste, or garbage, per year.  Most of it can be safely dumped into a compost pile.  However, meat or meat products (juices, grease, gravies, bones) or any dairy products (cheese, whole eggs, sour cream, milk) present some problems if they are included in a passive composting system (no high temperatures).  So do products high in fat such as salad dressings, mayonnaise, and peanut butter.  If you use the passive approach to composting, it may be unwise to include them in the system unless you take certain precautions (see page ###).  While they will decompose eventually, they can smell bad in the process.  Worse, if not properly handled, they attract pest animals such as rats.  If you use the active approach to composting, all forms of kitchen wastes can be successfully composted.


[Photo - Kitchen garbage in pail under the sink in a kitchen]


            Certainly non-meat leftovers or peelings of vegetables and fruit--and even egg shells--can go into any compost pile.  So can common garbage items such as coffee grounds, tea bags, and soggy paper napkins.  Be sure to mix large amounts of kitchen waste, which is mostly green and high in nitrogen, with some kind of dry carbon material such as chopped leaves, brush or wood chips to prevent any odor problems. 


            Raw food scraps are potentially a very good fertilizer from the point of view of their NPK content.  Consequently, food scraps which have been liquefied in a blender can be spread directly on to a garden bed or under a shrub to be absorbed by the soil and processed there by its microlife.  Later in this chapter we will show you several composting systems designed to handle any kind of kitchen garbage with no odors or pest problems. 


   NPK Percentage Value of Kitchen Garbage In Compost

            Nitrogen                         Phosphorous                        Potassium

            2.0-2.9                                    1.13-1.30                        0.08-2.2


            Woody materials

            Woody materials such as wood chips, pine cones, and cleared brush, even when shredded, take a long time to decompose.  If you have large volumes of this kind of material, consider using them as a mulch or composting them separately so that they can rot completely without tying up the regular compost pile.  Heavy duty shredders will shred sticks and limbs finely enough so that they, in reasonable amounts, can be routinely incorporated into a regular compost pile.  The compost may have a slightly coarser texture, but it will be fine for use in all situations. 


[Photo - Someone chipping a 2 inch branch in a big shredder, producing wood chips]


   NPK Percentage Value of Wood Materials In Compost

Nitrogen                         Phosphorous                        Potassium


            Some composting references suggest interspersing sticks and brush among the other materials in a compost pile to facilitate the access of oxygen to the center of the pile.  While the sticks  will definitely perform that function, they also clutter up the compost as it gets close to final maturation.  Those sticks have to be sorted out of the final product and as far as we are concerned they are more nuisance than help.  There are other ways to get oxygen into the pile.  We recommend you keep sticks and limbs that are not shredded out of the compost pile.


            Several trees produce chemicals in their wood that makes it unsuitable for a compost pile.  Woodchips or sawdust from black walnut, red cedar and eucalyptus have a negative chemical effect on certain landscape plants and even after composting can inhibit plant growth. So use wood chips from these trees only in permanent pathways or driveways. 


[Photo - Truck of tree company filled with woodchips from big shredder attached to the back]


Other Household Organic Wastes



            Occasionally, a landscaping project or lawn renovation  requires the removal of sod from lawn areas. Sod makes perfectly good compost, but does require a year or two to become fully decomposed.  There are two alternatives for composting sod. Dampen the pieces and stack them, grass side facing down, into a pile.  Throw a tarp or other cover over them to keep out light and after about two years the pile will be mostly compost.  The faster method is to run the sod through a heavy-duty shredder and incorporate the results in a regular compost pile, with lots of carbon material. 


[Photo - Sod piled upside down to compost]


            Paper From The Home

            A large portion of the waste generated by American households today is paper in one form or another.  Many communities are developing recycling programs to collect paper separately so it does not enter the regular waste stream.  However, much of the paper coming from homes can be composted.   Newspapers are now universally printed with water-based inks so they are perfectly safe to compost and use around the landscape, even in the vegetable garden.  Magazines that are printed in color on a glossy paper stock are more problematical.  Those materials may still have inks that are unsafe for plants, so do not reuse them as a mulch or include them in a compost pile.  The kind of paper a home office generates from the computer or copy machine is suitable for composting.


[Photo - Someone with paper shredder shredding paper]


            The secret to composting paper is to shred it first.  The ideal tool for this job is an electric paper shredder used in many offices today.  There are also hand operated paper shredders that work fairly well, but they require a bit of manual energy to function.  A large general purpose landscape shredder will handle newsprint and other paper.  Do the job when there is no wind at all.  Otherwise, you will have bits of paper all over the neighborhood.  We feel that best use of shredded paper is not in the compost pile, but rather as bedding in a worm farm, which is just another form of composting system.  See details in chapter ##.


            Wood Ashes

            If you have a wood stove or use a fireplace frequently, you have wood ashes to dispose of from time to time.  You can use these wood ashes from the fireplace or wood stove in the compost pile, but use them sparingly.  They are most useful when you are trying to compost acidic materials such as pine needles or oak leaves, then wood ashes in the pile will help bring the compost to a more neutral pH level, while adding some mineral value to it in the form of potassium and some phosphorous.  At the same time, the ashes, as with limestone, will cause some loss of nitrogen in the final compost product.  Do not add much more than a gallon pail or two to any normal-sized compost pile to avoid producing very alkaline compost. 


[Photo - Person cleaning out a woodstove]


   NPK Percentage Value of Grass Clippings In Compost

Nitrogen                         Phosphorous                        Potassium

                                    1.0                                    6.0


            Human Waste

            In many parts of the world, human waste is recycled back on to agricultural fields as a major source of nitrogen and other nutrients.  This practice provides fertilizer for the farmer, but risks introducing certain human diseases into the food chain in those countries.  That said, it is possible for people living in North America to compost their own wastes without risk of infecting anyone else or themselves with disease pathogens at a later date.


            Do not attempt to compost human waste in a compost pile, however. If it is important to you to recycle this organic material as well, then purchase a "waterless toilet".  Sometimes called a composting toilet, these devices are designed to compost  human feces. Several types of composting toilet are on the market.  Models range from large units that rely solely on the natural processes of decomposition to smaller ones that are aided by electricity.  A composting toilet collects human waste, and even kitchen wastes too, and composts it inside the device.  The final product is a rich compost that is appropriate for use anywhere in the landscape.  We recommend that such compost not be used on food crops, not because there is any obvious hazard, but because we probably don't yet know enough about homemade compost to be absolutely sure there is zero danger in using it for that purpose. 


   NPK Percentage Value of Human Waste In Compost

                        Nitrogen            Phosphorous            Potassium

Urine                          15-19%              2.5-5%              3.0-4.5%

Feces                          5-7%                          3-5.4%              1-2.5%


            Human urine is a potential candidate for use directly in the home compost pile.  Urine from a healthy person is sterile and contains no pathogens that can be transmitted to others.  Urine contains a great deal of nitrogen so can be used to accelerate the decomposition in a compost pile made up mostly of carbon rich materials such as chopped leaves.  Sprinkle it on the pile in its normal strength or dilute it up to 5 to 1 with water.  Sprinkled on a pile as it is built or turned, it will not cause any odor.  Undiluted human urine simply poured on top of the pile may have some residual odor for a day or two, but otherwise it causes no problems. 


[Photo - Little kid sitting on a pottie (grin) ]


            Miscellaneous Items

            In sum, almost anything that is organic can be composted.  That means there will always be some miscellaneous items around the house that the avid composter can safely add to the compost pile to help reduce the volume of waste materials going into the municipal waste stream.  For example, the contents of the vacuum cleaner bag is perfectly good material for composting.  Cloth products such as worn out sheets, towels, diapers (clean) and clothing items can be composted, though it is best to cut them into very small pieces before introducing them into the pile.    Avoid fabrics that may have chemicals in their finish.  Basic cotton material is the safest bet.


Composting Materials to Forage Away From The Home


            If you have a need to get into composting in a big way, and are looking for much more material than your own home can supply, there are many other sources of composting materials in the community, whether you live in the city, suburbs, exurbs, or country.  Farms and stables are a source of spoiled hay or straw and of various kinds of manure.  Other materials can be found at grocery stores, factories, mills, restaurants, and many retail operations.  Only your imagination, dedication, and the size of your truck will limit your access to organic materials that can be composted. 



            Early books and articles about making compost all praise the value of manure, any kind of manure, in the compost pile.  What is unfortunate of course is that most of us have absolutely no access to manure for any purpose.  Animal manures are all very high in nitrogen, so when mixed with a high carbon material such as chopped leaves or hay, they produce wonderful compost which also has some important fertilizing value.  Notice in the table that dried manures tend to be richer in most major nutrients than fresh manures.  Manure in the form of bedding material that has both excrement and urine is better than just the excrement alone.  The urine offers a high nitrogen value and the bedding material usually contains high carbon values so the C/N ratio is already moving towards balance. 


[Photo - Cows or horses standing around a manure pile]


   NPK Percentage Value of Manure In Compost

                                    Nitrogen            Phosphorous            Potassium

Poultry, fresh            1.63                        1.0-1.5                        0.60-1.0

Poultry, dried                                    1.5-2.0                        1.2

Hog, fresh                        0.60                        0.45                        0.5

Horse, fresh                        0.44                        0.35                        0.3

Horse, dried                                                1.0                        1.6

Cow, fresh                        0.29                        0.25                        0.1

Cow, dried                                                1.0                        1.5


            Manures, especially bedding manures, are likely to have a high number of weed seeds from the material eaten by the animal and from the bedding material.  Therefore, it is probably wise to use manures only in active composting systems in which the temperatures will reach in excess of 140 F, required to kill most weed seeds. 


            Animal manures will vary considerably in their nutritive value from animal to animal.  Chicken manure is the richest animal manure in terms of NPK.  Chickens do not excrete urine separately, as mammals do.  Consequently, the very rich chicken manure must always be composted before being spread on to the garden.  Fresh chicken manure will burn any plants coming in contact with the stuff.  Horse manure is also quite rich in nitrogen and should not be used directly on the soil in fresh form.   Cow and pig manure is not considered so "hot" and if spread immediately around the garden, it is not likely to cause any harm.  In most cases however, just to avoid the odor if for no other reason, it is best to process manure first through a compost pile before being used in the yard and garden. 


            Ruined Hay or Straw

            Either straw or hay makes a terrific carbon base for a  compost pile, especially in areas where there are few chopped leaves to be had.  Hay is grown by the farmer to be harvested as food for livestock.  It is usually processed into bales for easy handling, transportation, and storage.  Straw is the residual stalks from oats, wheat, and other grains that have been harvested and processed.  The dried stalks of the plant are often baled and used as bedding material for livestock.  In both cases, if the hay or straw gets wet it loses its value to the farmer.  His loss is a composter's gain.  This spoiled material is perfect material for composting. 


[Photo - Farmer's field with some hay bales just sitting there]


            Hay has more nitrogen value than does straw, but they both are valuable additions to the compost pile.  Their only drawback is that they may bring in some weed seeds that were gathered up in the baling process.  If you have an active composting system, that is no concern.  If you use the passive composting method, you may want to give your straw or hay-based pile one turn during the composting period to try to reduce the weed seed problem.  We have found that while you can use the straw or hay as is in the compost bin, it works much better if it has been shredded first.  Use any kind of a shredder or even lay it out on the ground and run the lawn mower over it. 


   NPK Percentage Value of Hay or Straw In Compost

                        Nitrogen            Phosphorous            Potassium

Timothy hay              1.25                          0.55                          1.00

Wheat, straw              0.50                          0.15                          0.60


            If you have a vehicle that can carry a bale or two of spoiled hay or straw, a drive out into farm country can almost always turn up a few bales that will cost no more than a dollar or two and may be free.  Watch for fields that have been harvested but have one or two or more lonely bales still sitting out there.  They are probably spoiled and the farmer is happy to get rid of them.  Another good source of straw is construction sites where contractors have used many bales of straw to control erosion during the earth moving phase.  That straw is of no value to the contractor after the job is finished and he will usually be happy to let you take it away. 


            Seaweed and Kelp

            People who live near the seashore have an excellent mulching or composting material in the form of seaweed that can be harvested along beaches and inlets.  This material is not terribly rich in phosphorus, but it has a relatively high level of nitrogen and lots of potassium.  Seaweed is amazingly rich in what are called the micro-nutrients; minerals such as zinc, iron, manganese, and many others essential to healthy plant growth.  Seaweed has about the same level of organic matter found in animal manures. 


[Photo - Collecting seaweed on the seashore]


   NPK Percentage Value of Seaweed In Compost

Nitrogen                         Phosphorous                        Potassium

1.68                                    0.75                                    4.93


            The only concern with seaweed is the salt content coming out of the ocean.  Either wash the seaweed off with a garden hose or let it sit out in a steady rain to solve the salt problem.  The more you wash it off however, the more you lose some of the micronutrients found on the surface area of the plant.  So rinse it, don't soak it.  Seaweed can be composted immediately in its green state or it can be dried (preferably under a roof of some sort) and then composted.  The dried material has a bit higher level of some of the nutrients. 


Industrial or Commercial Wastes


            The following composting materials are offered to give the reader an idea of the variety of sources of material that exist throughout the country.  These sources are for people who want to have large volumes of compost.  Some of these materials are available for free while others may cost a nominal amount.


            Beet Wastes - Wastes from sugar beet processing companies make good compost. 


   NPK Percentage Value of Beet Wastes In Compost

Nitrogen                         Phosphorous                        Potassium

0.40                                    0.40                                    3.00


            Corncobs -- Corncobs make excellent compost however they it is important to shred them before adding them to the pile.  Fresh corncobs are harder to shred than cobs that have left out in the weather for a few months. 


   NPK Percentage Value of Corncobs In Compost

Nitrogen                         Phosphorous                        Potassium

0.0                                    0.0                                    2.01


            Felt wastes -- Companies that make hats generate a certain amount waste hair, felt, and wool.  They may have as much as 14% nitrogen and make good composting ingredients. 


   NPK Percentage Value of Felt Wastes In Compost

Nitrogen                         Phosphorous                        Potassium

3.80                            &nbs

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