Backyard Composting With Practical Tips From The Pros
Compost, a soil additive created by mixing things like plant-based kitchen scraps and yard waste, adding air and water and allowing them to be broken down by bacteria and fungi, is highly valued by knowledgeable gardeners. Composting is gardening alchemy. It turns waste products into gardening gold. Adding organic matter to the soil increases water retention and reduces nutrient leaching in coarse (sandy) soils while improving drainage and balancing air and moisture in fine (clay) soils. Compost reduces the bulk density of soil, making it easier for roots to penetrate. It provides food for micro-organisms that help plants capture nutrients. These same microbes help control diseases and degrade pesticides in the soil. Its humic acid content even helps reduce drought stress in plants. To top it all off, composting uses materials that all households generate and keeps them out of landfills, helping reduce waste disposal costs and extend landfill life.
With all these benefits, it just makes sense for gardeners to compost. The most productive way to compost at home is called “hot”composting. It is a pretty simple process whose dos and don’ts can be summarized in a few points:
- Composting can be done in a pile or simple wire or wooden bin. Recommended size for a hand-managed compost pile is a 3 or 4 foot cube. Site it in an inconspicuous location, a distance from the house in the event it draws critters or emits odors.
- Start with a 3 inch base layer of coarse plant material, twigs etc to enable bottom up aeration
- Build the pile with a 3 to 1 mix by volume of brown to green material. That’s brown for carbon, green for nitrogen.
- Browns can include: leaves, sticks, untreated wood shavings, food soiled paper, hay/straw, dead plant material.
- Greens can include: fresh grass clippings and plant materials, coffee grounds, fruit/vegetable kitchen scraps, manure (not from pets), hair.
- Items not to compost: meat/grease/bones, dairy products, eggs, pet waste, diseased plants or trimmings, pesticide treated materials, weeds with seeds, charcoal or coal ash, black walnut leaves/twigs, pressure treated wood materials.
- Chopping or shredding the materials speeds the composting process. Use your lawn mower, string trimmer etc.
- Layer the browns and greens, then mix them to start the process. Commercial compost starters are available, but are generally not considered necessary for success.
- Mix the materials regularly to aerate them. The composting process requires oxygen. A good mix of materials will heat to 140 degrees or more, then will begin to cool. The pile should be remixed a few days after peak temperature. Continue the regular mixing until the pile is completely cooled.
- Add water to keep everything moist, not wet. About like a wrung out sponge.
- When complete, the compost will be dark and crumbly, smell like good soil and the pile will be cool.
- If the pile gets smelly or slimy, it is too wet or has too much green material. Add brown material and turn the pile to mix it in.
- In dry weather, keep the center of the pile lower than the edges, so it will hold more moisture and reduce the need to moisten it manually.
- Diseased or insect-infested materials can be composted, but the pile must get “hot” to kill insects or pathogens. Probably best to dispose of such materials rather than compost unless you are sure your pile gets up to about 140ºF.
- Some sort of bin to contain the compost materials, although not essential, is a good idea. It controls the materials, makes a neater presentation in the landscape and may help keep animals out of the pile. It can be any kind of structure from wood to wire to purchased composting bins. Make the call based on your specific situation.
Tips from the Pros
As part of the research for this article, we visited two local commercial composters. Rather than seeing home composters as competitors, the commercial folks see us as allies. They are true believers that putting organic material back in the ground is essential to making progress on the world’s food security problems. The gardening public seems to understand this since both companies are more worried about finding the volume of materials they need to make their product, than they are about selling what they make.
Both of these compost operations use leaves and wood chips from yards and municipalities as their carbon sources. One gets his nitrogen from food waste collected from universities and restaurants, the other uses turkey litter (manure and bedding) from a commercial turkey grower. Both mix their materials and build windrows — long narrow piles — that they monitor for temperature. They mix the materials using power equipment to keep the rows aerated during decomposition. Typical cycle for a well-managed hot compost batch is 3 ½ to 4 months. When the row is cool, they screen it to get chunks and non-decomposed material out of it, and offer it for sale. Organic commercial compost is tested for pathogens, but our sources really don’t worry about lingering disease or weed seeds in their material because they monitor temperature closely and are confident that their material is pathogen free. Their biggest concern is receiving material that contains herbicides that could damage crops when applied as compost. So they do their best to publicize the need for herbicide free feeder materials from the municipalities and landscapers who supply them.
When asked for advice for the home composter, their tips were insightful:
- Hoard your carbon materials. In the typical home, you’ll have plenty of nitrogen sources; food materials are available all year around, and grass clippings are available in the spring through fall. But the carbon materials you need are often less plentiful. Leaves, a key carbon source, are available in the late fall into winter. Gathering the right mix of materials to initiate a compost batch takes some planning and the carbon materials are the key.
- Successful composting requires a nitrogen source, a carbon source, air and water. Include chunky materials like wood chips in the mix to reduce bulk density and maintain some air flow in the pile. Turn it regularly for the same reason. Including woody materials requires that the compost be screened prior to use, but the extra effort is worth it to support the decomposition process.
- Water also has to be controlled. Too little starves the process and too much limits air availability. Serious composters cover their piles, preventing over or under moisturizing by adding water manually as needed. Again, the guidance is to keep it about as moist as a wrung out sponge.
If all these rules and procedures are beyond what you are prepared to commit to, don’t despair. There is also room in the world for less-motivated folks to compost. For many of us, the most practical way to go forward is to toss appropriate materials into the bin as they become available. This prevents preparation of the properly proportioned batches needed to achieve hot composting. The materials will take longer to break down into usable form, typically a year, maybe longer. But if you turn it and check moisture periodically, you can create a great product and still put the otherwise disposable materials to good use. If you know you are not going to maintain a hot pile, resist throwing weed seeds and diseased plant materials into the mix because you won’t reach the temps needed to kill them. If you add materials to your compost batch as they become available, you will tend to have usable compost at the bottom of the pile and newer not yet ready material at the top. It is not unreasonable to scrape the newer uncomposted product off the top of the pile and use the fully composted, older product, or screen everything. Use the good stuff now and put what isn’t yet ready back into the bin for further decomposition. In any case, providing both carbon and nitrogen sources and managing aeration and moisture is still essential.
A Final Word
It was eye-opening that both commercial composters worried more about their raw material supply than selling what they produce. In fact, one of them has since closed his operation because he couldn’t acquire enough compostable material to reach a break-even volume level for the business. It is admittedly extra work for restaurants, for example, to sort compostables from other food wastes, and kitchens get busy…
On the other hand, about 20% of material going to Virginia landfills is food and yard waste. Imagine converting that to a sellable product that provides wonderful benefits to soil, enhancing food production and beautifying landscapes. It will likely take legislation to create anything more than creeping change in this situation, and this seems unlikely in the short term. But maybe we small time composters will help to create the cultural shift that will make it possible in the future. At least we hope so.
“Compost: What is it and what’s it to you?” pubs.ext.vt.edu/452-231_pdf
“Using Compost in Your Landscape,” pubs.ext.vt.edu/426-704.pdf
“Making Compost from Yard Waste,” pubs.ext.vt.edu/426-703_pdf.