3-Bin Composting
How To Compost at Your Community Garden
Maintaining an active compost system allows us to benefit from our plant and food waste while reducing the amount of valuable materials that need to be removed from the site. I’m going to explain how we compost at the Garden City Harvest community gardens, but if you’re a home composter or just interested in how compost works, this is a great place to start!
Community Gardens Coordinator, Rye, found some non-compostable objects while turning this pile!
What is Compost? How does it work?
The various bacteria, fungi, and insects that naturally inhabit the soil break down the material into fine particles that act as an excellent natural fertilizer. I know what you’re thinking - compost sounds smelly! And yes, compost can get stinky if things get out of balance. To avoid smells and keep that compost happily trucking along, you need to:
Add the correct amount of materials containing nitrogen and carbon
Turn the compost to promote oxygen flow
Add enough water to keep the cycle going
Nitrogen and carbon come from “brown” and “green” materials. Brown materials include straw, dry leaves, pine needles, and wood chips. Green materials include kitchen scraps, plants and debris from your garden (excluding most weeds), fresh grass clippings, and fresh leaves. It’s best to maintain a ratio of 2 parts brown materials to 1 part green material. Make sure the pieces you add to your compost are small. Smaller pieces breakdown faster. Typically, compost with too much green material produces the most smell - too many greens can lead to your compost being wet and slimy — the greens are filled with water and need the brown to balance them out!
Benefits of compost
Composting diverts organic waste from landfills. All those food scraps and plant materials, when they go into a landfill, are compressed in an anaerobic environment (lacking oxygen) and actually produce methane gas. By composting instead, you’re reducing greenhouse gases and diverting that material into something beneficial.
Composting also keeps a valuable resource in a closed loop system. Instead of removing all those good nutrients contained in plant and food matter, you’re returning them to the ground where they will enhance the soil structure, improve water retention and nutrition content, and regulate the pH levels in your soil. All of this will reduce dependence on synthetic fertilizers, because you’re helping build a healthy soil community that can adequately sustain your plants without outside inputs.
Now that you know the basics of composting, here’s how we compost at the Garden City Harvest community gardens.
“Maintain a ratio of 2 parts brown materials to 1 part green material”
A four-bin compost system at the Bitterroot Line Community Garden. Fresh material is added to the left-most bin and turned to the right until it’s fully “cooked” in the right-most bin, where a gardener is taking some to add to their plot.
The 3-bin system
At most of our community gardens, there is a three (or four) “bin” system for the compost. Each of these bins represents a different stage of the composting process - look out for green signs on or above the bins labeling these stages. The compost progressively decomposes as you move it from bin to bin, finally resulting in a dark, crumbly soil you can add to your plot!
Start
This bin (usually on the left side) is where food scraps and garden waste should be added. As much as possible, try to chop up your materials, either before you add them, or with a shovel in the bin. The smaller pieces will speed up the composting process! As you add this “green” material, layer in straw to get that 2:1 brown:green ratio. Most gardens have a designated area next to the compost for used straw; this straw is meant for you to add to the compost! Additionally, this bin should be watered at least once a week (or more frequently if it dries out quickly). The moisture will aid the decomposition process.
Once the pile is a few feet high, you can turn it into the next bin - cooking.
Cooking
All of our gardens have a pitchfork in the shed that is perfect for turning the compost. Use the pitchfork to lift the compost in chunks and flip it into the next bin. This will add oxygen into the pile, making decomposition move more quickly. You’ll be able to see how material on the bottom of the pile has already started to break down.
Some of our gardens have one cooking bin, and some have multiple. In these bins, the compost is continuing to break down. Don’t add new material to these bins, but continue to water them, and mix them with a shovel or pitchfork to add oxygen. As the material decomposes more, and when it looks and feels like soil, you can add it to the last bin…
Done (& sift!)
This is finished compost ready to add to your garden! Look for a mesh soil sifter beside the compost or in your shed - you can strain the compost through this to remove any remaining large debris before you add it to your plot. Compost can be mixed in to your soil at the beginning or end of the season, added when planting, or used as a “top dressing” on the soil surface around your plants after planting - as you water, the nutrients will seep down to your plants’ roots. While it’s certainly possible to add too much compost, this amendment is much more balanced nutrient-wise than manure or fertilizer, so you can add multiple 5-gallon buckets to your plot over the course of the season.
Here are the signs you will see at our community gardens designating what should happen in each bin.
What can we compost?
Most of the material that grows in your plots and the majority of your kitchen scraps can be composted or incorporated into our plots. If you are a gardener with us, you’ll see the blue graphic on the left posted at your garden compost.
- Garden waste (leaf material, stems, flowers, etc.) and kitchen scraps are great additions to the compost piles. Make sure that these items all find their way to the correct compost pile; they are a valuable resource!
- Weeds that have not yet flowered or gone to seed. Make sure that you keep up with your weeds and don’t let them flower and go to seed. If you’re confident in your weed ID, most of your weeds can be incorporated into your plot or added to the compost system - with the exception of a few troublesome weeds, like bindweed, quack grass, shaggy soldier. If you’re unsure about which weeds are safe to add to the compost, then do the safe thing and just add them to the weed pile.
What can’t we compost?
Weeds that have gone to seed should be placed into the separate weed pile to be removed from the site. Adding weed seeds to the compost will increase the weeds in your garden and exasperate future maintenance issues. Don’t add quack grass to the compost, as it can re-root and come back to life!
Stalks or woody material (corn stalks, brassica stems, sunflowers, and shrub or bush prunings) should be added to the weed/stalk piles. Large woody material decomposes very slowly and will hamper the composting process.
Meat and dairy products should not be incorporated into our composting systems. These items can lead to a messy and stinky pile, and can also attract pests and critters that may be a nuisance or carry diseases. Additionally, our compost won’t get hot enough to properly break down animal products.
Plant material that is diseased or infested with pests. In order to reduce pest and disease issues at our garden sites, infested and diseased plants should be removed from the garden site (thrown away).
Commercially compostable items like plates, utensils, etc. These items can only be broken down in industrial composting facilities, like Garden City Compost.
Above: beautiful dark finished compost in the middle bin; community gardeners excited about compost care!
Go forth and compost
Now you know the basics of how to compost at your community garden site! If you’re interested in maintaining it (and we hope you are), reach out to your garden’s Leadership Committee. In no time you’ll be able to reap the rewards and see the benefits of this fascinating process.
***To get involved in compost maintenance as a Garden City Harvest community gardener, reach out to your Leadership Committee (contact info in shed) or Garden City Harvest staff. Successful composting is a whole-garden effort, and we want all hands on deck!