13 Common Composting Myths

Before stating your own pile, it is important to get the facts straight on what a compost pile is, how it works and all the dos and don’ts. This task can be overwhelming, so we’ve gathered our top 13 tips to help you get the compost started.

Myth #1: Bagging and composting grass is your only option.

Try “Grasscycling” or the “Don’t Bag It” system instead of using mulching mowers or bagging. There’s no reason to bag grass if you cut it more often, use less fertilizer and leave the grass higher. Composting is a last resort in terms of managing grass clippings and should be practiced only when mulching is not practical, unless you want to make compost.

Myth #2: A compost bin is a compost bin.

Not all compost bins are the same. You might regret purchasing or building a compost bin that is not suited for your composting needs. For example, consider a worm box instead of a compost bin for table scraps. A pile serves to create heat and moisture.

If your goal is to “hold” materials such as leaves for a year or so, a large open-air bin is most practical. For active, hot composting, smaller enclosed plastic bins are preferred. Bins with sidewalls may make turning more difficult. Wire bins may rust and decompose quickly.

Myth #3: You can only form layers inside the bin.

Even if you are using a passive composting system, it is better to mix ingredients together outside the bin first. The act of forking everything over into the bin, mixing it all together as it goes, is the key step. Layers of organic material will not cook or heat properly until they are mixed. While it may seem that mixing materials together is extra work, this initial mixing stage can eliminate the bothersome job of turning a ripe pile in order to mix it later, and mixing in the beginning prevents foul order.

Myth #4: Topsoil inoculates the compost pile.

Old compost is a better inoculator than topsoil. Adding soil to a compost pile is like adding soil to a campfire – it puts the fire out! Topsoil adds no “fuel” to help the composting “fire.” The idea behind adding soil is to inoculate the pile with a healthy culture of soil organisms that colonize the pile and “jump start” the active, hot composting process. The best source of this inoculator, however, is older compost. The trick is to always save some old compost from previous batches to mix in with the fresh material.

If this is your first pile, try old leaf mold from under trees or purchase a few bags of composted manure from the garden center. Adding a little packaged inoculator may help if it contains an active biological culture. A rich, loamy garden soil should be used only as a last resort for the very first pile, never as a standard ingredient.

Myth #5: Adding lime can benefit your compost.

There is never a need to add lime to a compost pile. It can actually make things worse. Compost goes through natural pH changes, including an acidic stage while the pile is active. A sudden rise in pH from adding lime can actually kill a whole generation of beneficial organisms. Lime also has the disadvantage of releasing and losing valuable nitrogen, which can actually create a foul ammonia smell. Lime may be added to acidic soils, but it serves no beneficial purpose in the compost pile.

Myth #6: Don’t add items that contain toxins.

Everything that was once alive will eventually decompose back into humus. It is impossible to determine what plant or animal products comprise the humus by analysis. Natural chemicals found in plant matter (walnut leaves, eucalyptus, oleander) that are toxic to plants or animals eventually degrade, and composting accelerates this decomposition process.

Myth #7: Build your bin on soil so microbes can enter the pile.

Most commercial compost operations work just fine on top of concrete and asphalt. The number of microbes that will enter the pile from beneath it is insignificant. Add microbes in the form of old compost as an inoculator when the compost ingredients are mixed instead.

Myth #8: Any type of worm is suitable for your compost.

If your pile is still young, the heat may kill the earthworms. Garden earthworms do little to assist the composting process compared to their cousins, the redworms. Not all worm species are identical, and in fact, of the 1,800 species of earthworms found around the world, only two species of redworms are used regularly to assist the composting process. These beneficial redworms must be acquired from a worm grower and added after the pile has cooled, and then the pile has to be kept moist.

Myth #9: Composting is what nature does with organics.

Nature does not build piles. Nature mulches in layers. Composting is a “pile making” behavior characteristic of humans that converts organic materials into a dark, crumbly resource that can be converted back into a layer as nature intended. Composting is perfectly “natural,” but piles are not nature’s way of degrading organic materials into humus.

Myth #10: Adding “such and such” accelerates composting.

Composting can never be accelerated – it can only be delayed. There is an optimum rate of decomposition that occurs when moisture, air, temperature and nutrients are properly balanced and blended. If any of the essential components to decomposition are out of balance, the decomposition rate can be slowed.

Those that practice passive composting (in which organic materials simply sit) think that the process takes longer than it really should. When adding moisture, mixing ingredients, inoculating, retaining heat or doing other activities that optimize the decomposition process, some think that they have “sped up” the composting process. But the fact is that they have merely eliminated some of the delays. Composting rates may be relative from batch to batch, and some materials decompose more quickly than others.

Keep in mind, however, that humus produced from slow decomposition is just as beneficial for the soil as organic matter produced from the best of the hot composting piles. Fast is not necessarily better.

Myth #11: Don’t add grass clippings that contain herbicides.

Grass clippings, even those treated with over-the-counter herbicides, are safe to use for composting. Even without composting, the common household herbicide 2, 4-D is not significantly toxic to established plants after a week or so. Fresh clippings may retain some high levels of herbicide if they are used as a mulch. Compost, however, is rarely used until six months or a year after it is made. Studies have shown that 2,4-D degrades by 87 percent within 10 weeks in the compost pile. Other studies show them to be non-detectable after six months.

Myth #12: Don’t add paper because it contains toxic metals and inks.

Paper products are safe to use in the compost pile. Numerous tests show that various grades of mixed paper and the heavy metal levels are virtually the same as a variety of other ingredients. The U.S. EPA has set limits regarding the concentrations of a variety of metals that can be safely used in the soil. Paper products are well below these levels.

Regarding the inks themselves, the amount of hydrocarbons in the ink is insignificant, and the composting process is widely used as a technique by bioremediation specialists for degrading a variety of hydrocarbons. The tiny amount of hydrocarbon solvents in paper will quickly degrade in the compost pile.

Myth #13: Black dirt or topsoil is better than compost.

Organic, fertile soils are living ecosystems that took thousands of years to become fertile by nature’s process of annual mulching. At first, the soils are rich in organic matter and are highly fertile. However, after depletion, a process that can occur within a few years or generations, it will take thousands of years to enrich the topsoil with organic matter again. We can accelerate this process of building up soil fertility by tilling in compost, creating living soils in a fraction of the time. Enrich the soil you already have with compost or remove the old soil and replace it with soil mixed with compost.