What To Use
What can go into your compost? What can’t? Choose the right ingredients for your bin or pile.
The raw materials that go into compost come from organic waste. These green, organic disposables can come from your garden, your kitchen, and even your home at large (see Coffee Grounds and Compost). The more of it you keep from the trash, the more you keep from landfills. According to the United States EPA, yard trimmings and food residuals together constitute 20-30 percent of the U.S. municipal solid waste stream. That’s a lot of waste to send to landfills when it could become beneficial, environmentally sound compost instead!
Efficient and easy to use! The composting bins and supplies available at Planet Natural will reward you with piles of rich organic matter to use in your yard, garden, or houseplants.
The best thing about making your own compost is that you can control what goes in it and keep the harmful stuff out (see Can you Compost Tomatoes?). You control the balance of ingredients and don’t rely on any one component, say the ubiquitous “forest products” that make up so many commercial grades of compost.
A variety of ingredients — brown and green — are needed in the pile. The more varied the materials in your compost, the richer the finished product, filled with micro-nutrients and diverse, beneficial microbial life, will be. Here’s our list with special considerations and no-nos:
Need Prep or Special Time
All of these items can be added to compost, but if you just toss them into a normal heap, they may still be there, virtually unchanged, a season or two later. Be prepared.
Composting Grass Clippings
Grass trimmings are the quintessential compost ingredient. But more than one composter has discovered, to his distress, that the grass he dumped into his compost pile, instead of decaying into a nice, dark, crumbly, humus-rich compost, has instead putrefied into a slimy, stinky mess.
Grass does indeed make a fine feed-stock for compost, but it easily compacts into an oxygen-free mat. Since it contains a high percentage of water (over 50%), it swiftly goes anaerobic in the absence of oxygen. To prevent this, it should be mixed with other ingredients in the bin or with soil or even sawdust before it’s added to the pile. At the very least, spread the grass out over the top of the pile.
Sawdust, wood chips, sticks and twigs (best shredded or chopped), and pine needles can be added to compost, but be aware that their carbon content is very high. They will require a long time and/or a lot of nitrogen to break down. Use them in only moderate amounts, and add them in thin layers or mix them in with other ingredients, so the maximum surface area will be exposed to air and to microbes. Sawdust, like grass clippings, tends to form dense, anaerobic clumps that resist composting, so this material, in particular, should only be sprinkled into a compost heap in thin layers.
From the Kitchen
Your kitchen can make a significant contribution. Fruit or vegetable trimmings, rather than going down garbage disposals and into the sewer system or septic tank, make excellent compost additions. Breads, cereals, hamburger buns, old oats whether quick or slow, rolled or cracked — in fact, grains of any kind or condition are fine. Coffee grounds add nitrogen, and tea is fine; toss them in with their bags or filters (unbleached coffee filters are preferable and the staples in tea bags can be troublesome). Prepared foods, excluding meats (unless you’re using an aerobic digester), can be composted but can make your heap harder to manage for odor and moisture content. Their presence in outdoor piles can attract pests. If you maintain a hot pile or bin, items including old ketchup, relish, soy sauce, and such are acceptable but only in moderation. They’re quite acidic and could play havoc with the pH balance in the bin if added in excess. A long list of other things — nut shells, egg shells, corn cobs and so on — can also be composted; they’ll just take a while to break down.
Materials to Avoid
Coal Ash – Most ashes are safe to mix into your compost pile, but coal ashes are not. They contain sulfur and iron in amounts high enough to damage plants.
Colored Paper – Some paper with colored inks (including newsprint) contain heavy metals or other toxic materials and should not be added to the compost pile.
Diseased Plants – It takes an efficient composting system and ideal conditions (extreme heat) to destroy many plant diseases. If the disease organisms are not destroyed they can be spread later when the compost is applied. Avoid questionable plant materials.
Inorganic Materials – This stuff won’t break down and includes aluminum foil, glass, plastics and metals. Pressure-treated lumber should also be avoided because it’s been processed with chemicals that could prove toxic in compost.
Meat, Bones, Fish, Fats, Dairy – These products can “overheat” your compost pile (not to mention make it stinky and attract animals). They are best left to large-scale anaerobic digesters and avoided entirely (with certain exceptions) at home.
Pet Droppings – Dog or cat droppings contain several disease organisms and can make compost toxic to handle. (Can you believe the state of Alaska actually spent $25,000 on a study to determine the effects of composting dog poop? – PDF)
Synthetic Chemicals – Certain lawn and garden chemicals (herbicides – pesticides) can withstand the composting process and will remain in the finished compost. Don’t put anything recently sprayed in your compost heap.
Most contemporary pesticides break down quickly enough so that if they were used even six months earlier, foliage or grass from affected areas can be included in compost heaps. One important exception is Clopyralid, a pesticide which in 2003 was discovered to persist in soil far longer than had previously been realized. Fortunately, it is not harmful to humans or animals, but it can be quite toxic to a number of different vegetables. Since it passes unchanged through the composting process, composting foliage contaminated with it ensures that when the compost is spread, so will the Clopyralid be spread.
Note: Though compost has an extraordinary ability to break down pollutants and pesticides, it cannot handle the quantities sprayed on recently treated grass. Acre for acre, ten times as many pounds of pesticides are used on American lawns as are used on farmland. In other words, when pesticides are applied on turf grass — including homeowner’s lawns — they are generally applied at very high rates. This is good reason to encourage your community to reduce lawn and park spray programs . It’s also why grass clippings should not be composted if they have come from a lawn where pesticides were used recently.
Weed Seed, Diseased Plants and Other Contaminants
Whether it is safe to include weeds that have gone to seed, or tomato plants that have been infected by disease or nematodes, depends entirely on how hot your composting system is and how long you keep it hot.
Many experts advise not to put diseased plants or weeds that have gone to seed in compost piles. That’s the conservative fail-safe position. If you want to be absolutely sure that you won’t spread weeds when you spread compost, don’t put weed seeds in the pile (not always an easy task). The same goes for diseases.
However, a good, hot pile will kill just about every seed and every disease pathogen you can throw at it. Indeed, one major study (PDF) concluded that “For all of the bacterial plant pathogens and nematodes, the majority of fungal plant pathogens, and a number of plant viruses, a compost temperature of 131°F (55°C) for 21 days was sufficient for ensuring eradication.”
here are several exceptions. Two common tomato diseases, tomato wilt (caused by the fungus Fusarium oxysporum f. sp. lycopersici) and Tobacco Mosaic Virus (TMV), as well as clubroot of Brassicas (caused by the fungal pathogen Plasmodiophora brassicae), all required 21 days at 149°F (65°C) to degrade. Even this news is not quite as bad as it seems; TMV appears to degrade at lower temperatures if it is given sufficient time.
A Word About Activators
Compost activators add nitrogen, microorganisms, or both to your pile. They provide a quick boost to the decomposition process. Nitrogen sources include alfalfa meal, cottonseed meal, blood meal, or finished manure. Naturally occurring microorganisms get a boost from a reputable compost starter. They’re a probiotic for your pile.
Also, you may want to add ashes from a wood-burning stove if you’ve added a lot of acidic materials such as pine needles and oak leaves. Wood ashes are alkaline and can help adjust the pH of your compost pile if it gets too acidic.
Speeding Up the Compost Process
Compost decomposes fastest between 120 and 160˚F, so anything that will increase the heat will “cook” your compost faster. Here are four tips for fast composting:
- Chop and shred larger items, which makes it easier for the bacteria to break them down. For example, one easy way is to slice and dice garden waste is to run your lawn mower over leaves and other garden waste. Take scissors to newsprint or cardboard.
- Turn, turn, turn.
- Give your compost heap a “big meal” versus small snacks. Collect all your organic waste over a couple of days and then add it in one big bunch. The more you add at one time, the more your compost will heat up.
- Keep your compost pile in the sun. The heat will speed up the process
What products to compost
You will be able to source all of the essential elements in order to build a great compost pile without having to look too far! As long as your carbon to nitrogen ratio is optimal (25-30:1) your compost pile will be breaking down properly. Here are some lists of acceptable additions:
Carbon Rich Material "Browns"
Cardboard (free of dyes)
Stems & twigs
Nitrogen Rich Material "Greens"
Kitchen food waste
Weeds (that have NOT gone to seed)
Things to Avoid
Diseased plant material
Manures from carnivorous animals
As for the rhododendron and holly leaves, you can definitely put them in your compost pile. However, it is a good idea to really chop or shred them up, as they take much longer to break down due to their fibrous and waxy make up. It really depends on how quickly you are trying to create usable compost. It might be a good idea to have a separate pile going that you incorporate those leaves into and another pile that you do not. That way you can have a pile you know will rapidly break down into garden goodness and have yet another ready to use later on. Good luck!
Alfalfa Meal (Organic)
Derived from sun-cured, non-genetically modified alfalfa that is freshly milled.
An easy and effective way to mix and add oxygen to the pile without heavy lifting.
Includes the microbes needed to speed up the decomposition of raw organic materials.