Composting organic material at your home can not only decrease the amount of material that you send to the landfill, it can also help turn your organic waste into healthy garden soil. In this section you will learn how and where to compost, the benefits of composting, and managing your food garden naturally.
What IS compost?
Compost is the end product of composting.
Composting is a degradation process brought about by bacteria and fungus organisms. Large amounts of organic kitchen, garden, lawn, and/or farm refuse can be reduced in a relatively short time to a pile of black, crumbly humus which makes an ideal soil conditioner.
Compost added regularly to soil will certainly benefit the soil. The soil’s structure will improve, since humus contains substances which cause aggregation (sticking together) of soil particles. In a clay soil this means that the microscopic individual particles will be clumped together and more air spaces will be opened up between clumps. Without these air spaces the clay particles stick tightly to each other, forming a nearly impenetrable barrier to water and gases. This is why clay is so sticky when it is wet and hard when dry.
In sandy soils, the large sand particles are clumped with humus too, the humus adding its nutrient- and moisture-holding capacity. Normally, water and nitrogen fertilizers leach quickly from sandy soil, making it necessary to add them frequently.
A less widely recognized benefit from compost is that it contains humic and other organic acids which help to degrade compounds naturally present in the soil into the simpler form that plants use. These elements, or ions, can then be held by the humus particles, which contain many ion exchange sites on their surfaces. The ions are released into soil water, and plant roots are able to take them up.
Because there are so many ion exchange sites on humus particles, humus increases the buffering capacity of the soil. This condition helps to prevent rapid leaching of lime and nutrients as well as reducing the effects of over-liming and over-fertilizing. For example, when a soil’s pH is increased too much by adding too many wood ashes, the most economical way to correct the condition is generally to add compost, which will absorb (take up on the surface) the extra ions that produce the high pH. (compost itself is somewhat acid because of the acidic products made by microorganisms.) In other words, compost buffers the effects of other soil additives.
Compost and other organic matter turns the soil dark brown or blackish and increases heat-absorbing capabilities to a small extent. Compost reduces soil erosion because it allows water to percolate into lower soil layers, rather than puddle on top and then run off. This quality also reduces crusting of soil. Compost provides food for earthworms, soil insects, and microorganisms, many of which will, over the years, help balance the populations of less desirable soil fauna. Mycorrhizal fungi, which have been proven to benefit plants
through their association with plant roots, are also prolific in high humus soil. Finally, the products from the breakdown of plant and animal refuse contain many fertilizing elements in and of themselves, including trace elements not available from commonly used synthetic fertilizers.
Composting is an easy, environmentally beneficial way to turn yard and kitchen wastes into a dark, crumbly, sweet-smelling soil amendment that will build your soil, increase garden production and do wonders for your landscaping.
- Save you money by lowering garbage bills and replacing the need for commercial soil amendments.
- Increase production by improving the fertility and health of your soil.
- Save water by helping the soil hold moisture and reducing water runoff.
- Benefit the environment by recycling valuable organic resources and extending the lives of our landfills.
Composting recycles organic household and yard waste and manures into an extremely useful humus-like,
soil end-product called compost. Ultimately this permits the return of needed organic matter and nutrients
into the foodchain.
Composting is widely believed to speed up the natural process of decomposition appreciably as a result of the raised temperatures that often accompany it. The elevated heat results from exothermic processes, and the heat in turn reduces the generational time of microorganisms and thereby speeds the energy and nutrient exchanges taking place. It is a very popular misnomer that composting is a “controlled” process; if the right environmental circumstances are present the process virtually runs itself. Hence a popular expression, “compost happens”.
Decomposition similar to composting occurs throughout nature in the absence of all the conditions that modern composters talk about; however, the process can be slow. For example, in the forest bark, wood and leaves break down into humus over 3-7 years. In restricted environments, for example, vegetables in a plastic trash container, decomposition with a lack of air encourages growth of anaerobic microbes, which produce disagreeable odors. Another form of degradation practiced deliberately in absence of oxygen is called anaerobic digestion- an increasingly popular companion to composting as it enables capture of residual energy in the form of biogas, whereas composting releases the majority of bound carbon-energy as excess heat (which helps sanitize the material) as well as copious amounts of biogenic CO2 to the atmosphere.
Benefits of Using Compost
- Produce your own rich, beneficial soil additive
- Discard less garbage and pay lower garbage bills
- Conserve earth’s resources
- Protect and improve your environment
Use compost on your yard and garden to improve your soil:
- Compost returns nutrients to the soil such as phosphorus, potassium, magnesium, zinc, manganese, iron and boron
- Compost improves the texture or "tilth" of the soil providing:
– Easier cultivation
– Better water retention in loose or sandy soils
– Better drainage in clay or other heavy soils
– Less plant distress from over wet or over dry conditions
– Healthier plants which require far less commercial chemicals
(fertilizers, pesticides etc.)
- Compost reduces soil diseases by feeding the soil a balanced diet
Compost is an attractive and valuable mulch that:
- Promotes weed and erosion control
- Protects plant roots from sun and wind damage
- Conserves water
Make and use compost at home –
SAVE $$ and RESOURCES:
- Lower garbage bills
- Free soil additive, replacing most yard and garden chemicals
- Lower water bills
- Less work weeding
- A feeling of achievement when your yard and garden are more attractive and you are doing your part to save resources – and replenish the earth
Facts About Composting
With these principles in mind, everyone can make excellent use of their organic waste.
The Biology of Compost
The compost pile is really a teeming microbial farm. Bacteria start the process of decaying organic matter. They are the first to break down plant tissue and also the most numerous and effective composters. Fungi and
protozoans soon join the bacteria and, somewhat later in the cycle, centipedes, millipedes, beetles and earthworms do their parts.
Anything growing in your yard is potential food for these tiny decomposers. Carbon and nitrogen, from the cells of dead plants and dead microbes, fuel their activity. The microorganisms use the carbon in leaves or woodier wastes as an energy source. Nitrogen provides the microbes with the raw element of proteins to build their bodies
Everything organic has a ratio of carbon to nitrogen (C:N) in its tissues, ranging from 500:1 for sawdust, to 15:1 for table scraps. A C:N ratio of 30:1 is ideal for the activity of compost microbes. This balance can be achieved by mixing two parts grass clippings (which have a C:N ratio of 20:1) with one part fallen leaves (60:1) in your compost. Layering can be useful in arriving at these proportions, but a complete mixing of ingredients is preferable for the composting process. Other materials can also be used such as weeds and garden wastes. Though the C:N ration of 30:1 is ideal for a fast, hot compost a higher ratio (i.e., 50:1) will be adequate for a slower compost.
The more surface area the microorganisms have to work on, the faster the materials are decomposed. It’s like a block of ice in the sun – slow to melt when it’s large, but melting very fast when broken into smaller pieces. Chopping your garden wastes with a shovel or machete, or running them through a shredding machine or lawnmower will speed their composting.
A large compost pile will insulate itself and hold the heat of microbial activity. Its center will be warmer than its edges. Piles smaller than 3 feet cubed (27 cu.ft) will have trouble holding this heat while piles larger than 5 feet cubed (125 cu.ft) don’t allow enough air to reach the microbes at the center. These proportions are of importance only if your goal is a fast hot compost.
Moisture & Aeration
All life on Earth needs a certain amount of water and air to sustain itself. The microbes in the compost pile are no different. They function best when the compost materials are about as moist as a wrung-out sponge, and
are provided with many air passages. Extremes of sun or rain can adversely affect this moisture balance in your pile.
Time & Temperature
The faster the composting, the hotter the pile. If you use materials with a proper C:N ratio, provide a large amount of surface area and a big enough volume, and see that moisture and aeration are adequate, you will have a hot, fast compost (hot enough to burn your hand!) and will probably want to use the turning unit discussed in the next section. If you just want to deal with your yard wastes in an inexpensive, easy, non-polluting way, the holding unit will serve you well.
To make compost regularly, it is helpful to have compost bins in some form. You can construct two bins out of planks or concrete blocks. Make the bins about 4 feet high, 4 feet wide, and as long as desired, and open at one end for easy access. Leave spaces between blocks or planks for aeration. Accumulate plant refuse in one bin while the composting process is taking place in the other. A third bin may be desirable for near-finished or finished compost storage.
A simple, portable compost bin can be made with three or four used freight pallets, which are simply stood on their ends in a square or open square and lashed or otherwise held together. This type of bin can be disassembled for easy turning and emptying and then reassembled around the new pile. A chicken wire cage supported by three or four wooden stakes will also work satisfactorily, but is less sturdy.
There are also ready-made and kit composters available, including slat-sided cylinders into which refuse is added from above and compost removed at ground level. Rotating barrels for easy turning are also available; gardeners who have limited strength may find either of these types easier to deal with than the standard compost bin.
Whichever type of compost maker you use, it’s a good idea to make use of the nutrients which leach out from under the pile. This is easily done by locating the composter in the garden (which also reduces hauling time) or under a large fruit tree. Or, if the compost pile is on a slope, trenching can direct the run-off.
Many different materials are suitable for composting organisms. Composters often refer to “C:N” requirements; some materials contain high amounts of carbon in the form of cellulose which the bacteria need for their energy. Other materials contain nitrogen in the form of protein, which provide nutrients for the energy exchanges. It would however be an over-simplification to describe composting as about carbon and nitrogen, as is often portrayed in popular literature. Elemental carbon – such as charcoal – is not compostable nor is a pure form of nitrogen, even in combination with carbon. Not only this, but a great variety of man-made, carbon-containing products, including many textiles and polyethylene, are not compostable – hence the push for biodegradable plastics.
Suitable ingredients with relatively high carbon content include:
- Dry, straw-type material, such as cereal straws
- Autumn leaves
- Sawdust and wood chips
- paper and acardboard (such as corrugated cardboard or newsprint withsoy-based inks)
Ingredients with relatively high nitrogen content include:
- Green plant material (fresh or wilted) such as crop residues, hay, grass clippings, weeds
- Poultry manure and herbivorous animals such as horses, cows and llamas
- Fruit and vegetable trimmings
The most efficient composting occurs by seeking to obtain an initial C:N mix of 25/30 by dry chemical weight.
Grass clippings have an average ratio of 10-19 to 1 and dry autumn leaves from 55-100 to 1. Mixing equal parts by volume approximates the ideal range.
Poultry manure provides much nitrogen but with a ratio to carbon that is imbalanced. If composted alone, this results in excessive N-loss in the form of ammonia – and some odor. Horse manure provides a good mix of both, although in modern stables, so much bedding may be used as to make the mix too carbonaceous.
For home-scale composting, mixing the materials as they are added increases the rate of decomposition, but it can be easier to place the materials in alternating layers, approximately 15 cm(6 in) thick, to help estimate the quantities. Keeping carbon and nitrogen sources separated in the pile can slow down the process, but decomposition will still occur.
Some people put special materials and activators into their compost. A light dusting of agricultural lime (not on animal manure layers) can curb excessive acidity, especially with food waste. Seaweed meal provides a ready source of trace elements. Finely pulverized rock (rock flour or rock dust) can also provide minerals, while clay and leached rock dust are poor in trace minerals.
Composting in the form of bioremediation can break down petroleum hydrocarbons, TNT and a variety of toxic compounds. This is the bacterial and in some cases fungal content of the compost, that possess the enzymatic properties to de-polymerize the complex man-made molecules. In other words, there is nothing about the composting process per se that adds or detracts from this, unless as noted above, by warming, to increase the metabolic rate of the constituent organisms.
Some materials are best left to high-rate, a thermophilic composting system, as they decompose slower, attract vermin and require higher temperatures to kill pathogens than backyard composting provides. These materials include meat, dairy products, eggs, restaurant grease, cooking oil, manure and bedding of non-herbivores, and residuals from the treatment of wastewater and drinking water. Meat and dairy products can be recycled using bokashi, a fermentation method.
Human waste can be composted by industrial, high-heat methods and also composting toilets, even though most composting toilets do not allow for the thermophilic decomposition believed to be necessary rapid kill of pathogens, such as Salmonella. This is not a problem, however, since composting toilets also incorporate the essential element of time required to reduce available substrate on which pathogens can feed, while increasing the growth of competing microbes. If these high temperatures are reached, the resulting compost can be safely used as a fertilizer for food crops and even directly edible crops provided it is not illegal in the regions where the sludge is applied. Careful filtration of the compost also prevents contamination.
Sheet composting is another method of making compost. A layer of organic materials of about 3-4 inches is spread over the soil, then covered with a 2-inch layer of soil. The organic material is allowed to decay at least three months prior to cultivating. Sheet composting on an unused portion of your garden in the fall can provide an enriched area for spring planting.
About Compost’s Carbon:Nitrogen Ratios
Everything organic has a ratio of carbon to nitrogen (C:N) in its tissues. See below for a list of C:N ratios of common organic wastes. It is the combination of materials that creates the ideal climate for compost microbes-a C:N ratio of 30:1. This combination, along with moisture, volume and surface area, is what makes a fast, hot pile. Some composters like to keep things simple and use the terms brown (carbon) and green (nitrogen), and follow the general rule of 1 part brown for every 2 parts green.
|Legumes (peas etc.)||15:1|
Other composters like to build their piles using a variety of materials and using the following formula to determine the C:N ratio of their compost pile. This balance is difficult to achieve exactly, but if you are interested, you can come close by combining materials and calculating the resulting (C:N) ratio. For example, mixing two parts green grass clippings (which have a C:N ratio of 20:1) with one part dry leaves will give you a C:N ratio of 33:1, very close to the ideal. The process is this: add 20/1 + 20/1 (the 2 parts green) with 60/1 (the leaves). The total is 100/3 or 33/1.
Let’s look at this another way:
60/1 + 20/1 + 20/1 = (100/3)/3 = 33/1
Using the C:N (C/N is another way to write it) ratios on this worksheet, see if you can work out the following problems. We’ll do another one for you. Keep in mind that all volumes are equal – each pile of material in the following problems is approximately the same size.
- Making a pile of 2 parts green grass, 1 part pine needles and 1 part fresh manure yeilds a C:N ratio of _____?
- 20/1 + 20/1 + 110/1 + 15/1 = 4 165/4 = 41/1
- Your pile is a mixture of 1 part straw, 1 part dry leaves, and 3 parts green grass. What is the C:N ratio? _____.
- You have all the waste from your yard and garden and you have some sawdust to add to the pile. The ingredients are: 1 part sawdust, 2 parts green grass and 1 part fresh weeds. The C:N ratio of this pile is _____.
- If you make your pile with 1 part manure, 1 part straw and 2 parts green grass. what is the C:N ratio? _____.
Troubleshooting Compost Problems
Problems can occur if conditions are unfavorable.
Some of the most common composting problems:
- Bad odors indicate that there is not enough air in your pile make more air holes in your pile, or turn the pile, or start a new one.
- Center of the pile is dry means there is not enough water in your pile. Make more air holes, and fill them with water, and the water will disperse throughout the pile. You can also water the pile as you turn it.
- Pile is damp, but only warm in the middle indicates that your pile is too small. Increase the size of your pile to at least four feet high and four feet wide.
- Pile is damp and sweet smelling, but remains cool indicates a lack of nitrogen, not enough green matter (like grass clippings) or manure. Cover the pile with black plastic for a few days, but be careful not to cook all your microbes. The pile also may need more water.
Why are you still bagging your grass?
After all, lawn maintenance is work… And bagging your lawn clippings is probably the most time-consuming part of the job.
Now, consider not bagging your grass… Gone is the hassle of stopping every 10 minutes to empty the mower bag, raking and wrestling with expensive trash bags. Instead of causing trouble, your clippings can remain on your lawn, working their way back into the lawn to enrich the soil, keep the temperature cooler, and save on watering.
According to Turf Experts, … Grass Clippings:
- reduce water evaporation from the lawn
- reduce lawn wear by creating a cushioning layer
- facilitate better growth by keeping the soil temperature cooler
There is one other important reason for leaving your clippings on the lawn. During the summer months, grass clippings can account for a whopping 16 percent of residential solid waste. With waste management costs rising and an environment to protect, it just makes good organic sense.
You may choose to collect your clippings every third time you mow, or every other time. Your compost pile will need grass too. Regardless, you are creating a savings for you and the environment.
Lawn Maintenance Tips:
- Don’t let your grass grow too long before mowing. The clippings should be no more than an inch long in order to fall onto the soil.
- Use a sharp mower blade (a mulching mower if you have one). The sharper the blade, the finer the clippings, the faster they decompose.
- Avoid over fertilizing your lawn. Too dense a growth will not allow your clippings to reach the soil to decompose.
- Remove excessive thatch before leaving your clippings on the lawn. Although one-half inch of thatch
is ideal, a thick layer will keep clippings from reaching the soil.
- Always mow your lawn when it is dry so clippings will be able to filter down to the soil without clumping.
I find that a real gardener is not a man who cultivates flowers; he is a
man who cultivates the soil. He is a creature who digs himself into
the earth and leaves the sight of what is on it to us gaping good-for-nothings.
He lives buried in the ground. He builds his monument in a heap of compost.
If he came into the Garden of Eden, he would sniff excitedly and say:
“Good Lord, what humus!”
~ Karel Capek, The Gardener’s Year, 1931