Published on December 17th, 2007 | by Stephanie Evans2
A Composting Feast for Your Organic Garden
Start composting to minimize your contribution to the world’s already abundant waste supply.
Compost, that rich and earthy matter, is the end product of a complex dismantling of organic materials by hundreds of organisms, including bacteria, fungi, worms, and insects. When you compost, you participate in a controlled version of what happens naturally in virtually all plant systems. When plants die, they fall to the ground and decay. Microorganisms in the soil below feed on this dead matter until gradually it becomes part of the soil. Nitrogen, potassium, and phosphorus are naturally produced in this process, which keeps the soil in a healthy, balanced condition.
Aside from reducing waste that goes into the landfill, making your own compost provides you with a rich, valuable fertilizer for use on your lawn and garden. Addding compost to your soil improves its structure and fertility and increases its capacity to hold water.
While nature’s course of composting is slow, controlled composting provides an optimal environment for micro-organisms to flourish so the process can be accelerated. To encourage the most active microbes, a compost pile needs the correct mix of the following ingredients: carbon, nitrogen, oxygen, and water. While almost any organic material is suitable for a compost pile, the pile should have a proper ratio of carbon-rich materials, or “browns,” to nitrogen-rich materials, or “greens.” Brown materials include dried leaves, straw, wood chips, and corrugated cardboard. Green, nitrogen-rich materials are fresh or green, such as grass clippings and kitchen scraps. The carbon provides energy for the microbes, and the nitrogen provides protein, though achieving the best mix is recognized as more of an art than a science.
Environmental Hazards of Organic Waste in Landfills
According to the EPA, yard trimmings and kitchen waste together make up 24% of U.S. municipal solid waste. When these otherwise biodegradable materials are disposed of with non-organic materials in landfills, they make up a toxic stew of greenhouse gases and leachates (liquids that accrue in and seep out of waste piles) that contaminate underground water supplies.
Of the approximately 2,000 landfills in the U.S. today, over 75% have no lining to protect the nearby groundwater from being contaminated by the traces of lead, mercury, cadmium, and other toxic contaminants emanating from landfills. The Fresh Kills Landfill in New York is one of the largest U.S. landfills—it leaks an estimated 1 million gallons of leachate into the surrounding water table every year.
Efforts to reduce waste in landfills by converting it into beneficial compost have inspired a new technology known as compost bioremediation. By these new methods, finished compost is used to decontaminate soils, ground and surface water, and air. Here’s how it works:
- Decomposing microorganisms digest and metabolize organic waste into rich and crumbly soil.
- These same microorganisms—when applied as mature compost to contaminated soil or water—efficiently break down, and in some cases eliminate—contaminants such as hydrocarbons, chemicals, solvents, heavy metals, pesticides, and petroleum products.
- The composting process also absorbs odors and degrades semivolatile and volatile organic compounds (VOCs), including heating fuels, polyaromatic hydrocarbons (PAHs), and explosives.
Composting allows for the binding of heavy metals that works to prevent contaminants from reaching water sources or being absorbed by plants. Compost is also being used in a very innovative way to combat the effects of erosion by preventing turf loss on embankments, roadsides, and hillsides.
Personal Benefits of Composting
Aside from reducing waste that goes into the landfill, making your own compost provides you with a rich, valuable fertilizer for use on your lawn and garden. Adding compost to your soil improves its structure and fertility and increases its capacity to hold water. You can successfully compost all forms of kitchen waste into a rich and inexpensive soil amendment for all of your green gardening needs.
Here is a short list of items commonly used for composting, divided into carbon-rich brown materials and nitrogen-rich green materials:
- Animal manure from herbivores
- Coffee grounds and filters
- Fruit trimmings—rinds, peelings, and cores
- Grass clippings
- Green leaves
- Hair and fur
- Shredded newspaper
- Seaweed (rinsed to remove salt)
- Tea bags
- Vegetable peels and leaves
- Cardboard rolls (shredded)
- Clean paper (shredded)
- Cotton rags
- Dry leaves
- Dryer and vacuum cleaner lint (avoid incorporating lint used with dryer sheets)
- Fireplace ash (NO coal-based ashes—toxic to plants)
- Leaves (dry)
- Newspaper (shredded)
- Nut shells (crushed)
- Pine needles (chopped or shredded)
- Sawdust (from untreated wood)
- Wood chips
- Wool rags
- Yard trimmings (dry)
- Vegetable stalks (seeds for hot piles only)
Eggshells are also a great source of calcium for your compost pile, though you will want to crush them into tiny pieces because they take quite a while to decompose.
Do Not Add
- Anything chemically treated
- Bird droppings
- Cat or dog feces
- Cat litter
- Coal-based ash
- Colored paper
- Dairy products
- Diseased plants
- Greasy materials like oil, salad dressing, and peanut butter
- Human waste
- Treated wood products
Some of these are toxic and hazardous to plants and humans, and, while some others would decompose eventually, they generate odors and attract pests.
Achieving cured, finished compost can take anywhere from a few weeks to a couple of years, depending on the method you use and the upkeep you provide.
- Hot, or active, compost piles are ideal for a quick composting turn-around, because they retain a healthy balance of carbon, nitrogen, oxygen, and water that allows hungry microorganisms to do their job. You can sink your hand down into a hot pile and literally feel heat emanating from the middle (a good range is generally 115-130 F). A well-insulated bin will promote the warm, damp environment needed for maintaining a hot pile. You will need to turn the pile and ensure that it stays a bit moist.
- Cold composting takes much less upkeep and is thus often referred to as passive, or untended. By this method, compost components from kitchen scraps sit in the bin and the pile is simply added to from time to time—generally little to no mixing occurs. These piles are often oxygen-deprived and saturated with moisture, and they become odorous if brown materials are not added to improve drainage and aeration.
Prepping Your Compost Stew. Mixing certain materials or changing their proportions will make a difference in the rate of decomposition, but you’ll find that everything decomposes more quickly if it is chopped up into smaller pieces before being added. Freezing and thawing some compost contents before placing them in your bin is also helpful for accelerating the process.
Moisture. Keeping your compost pile about as damp as a well-wrung sponge provides the ideal moisture for bacteria and other micro-organisms to survive and will help your compost generate the optimum heat. To adequately aerate your pile, layer green and brown materials as you add them and turn the heap with a pitchfork or shovel, bringing the outer layers to the inside. Some compost bins come equipped with handles for turning and some have a round design to facilitate this process. When all the material has turned into dark brown or nearly black crumbly matter and the pile has cooled, your compost is ready to use.
Ratios. The ideal ratio of brown to green material in a compost pile is 25:1, though many people find three parts brown to one part green works quite well. High nitrogen content materials include green plants, animal manure, fruit and vegetable trimmings, coffee grounds, and seaweed rinsed to removed residual salt. High carbon content materials include dry straw-type material, autumn leaves, sawdust, and wood chips. If your compost pile has too much carbon material, it will break down too slowly, but too much nitrogen material can cause odor.
Bins. You can build a simple bin or box to hold your compost or you can choose from the array of commercially available box or barrel-style composting bins and tumblers. If you would like to make your own, the Montana State University Extension Program provides very detailed instructions for building several types of composting bins. When constructing your own model, keep in mind that adding a screen underneath your bin can allow for drainage and aeration, while keeping pests at bay. Many other resources for composting supplies can easily be found online.
Composting is the most simple and satisfying way to reduce garbage because we get to lend Mother Nature a helping hand with the recycling process. Eliminating organic waste from the stream of garbage being poured into our landfills is one of the primary steps toward achieving independence from our reliance on landfills as repositories of everything we discard. Composting is a step away from the estranged relationship we have had with our garbage in the past, and gives us a means toward achieving a zero waste approach for the future.
Article Contributors: Julie Reid