Compost: Turn food waste into soil nutrients!
Compost is an important soil amendment made of decomposed plant matter including food scraps. You can make right it in your backyard!
With the right recipe, your compost heap will not omit bad odors, will lighten the load (and cost) of your trash, and will greatly reduce greenhouse gas emissions from landfills.
Adding compost to soil helps to restore the organic matter content allowing for greater moisture and nutrient retention and providing necessary food for essential microorganisms that live in healthy soil. Read The Living Soil - Microorganisms to learn more about soil microbes.
Develop your recipe
A compost pile built with the right recipe of ingredients is like an open invitation to all of the critters and microorganism to join your compost party. If your recipe is right, they’ll come and do the work for you, and rather quickly at that! A pile built with the wrong ingredients will result in no one coming to your compost party, or worse, will result in only stinky anaerobes or large mammals following the smell!
There are two categories of materials that make up the ingredient list: Carbon materials and nitrogen materials. All matter contains carbon and nitrogen but for simplicity think of it this way: green materials (mostly nitrogen) and brown materials (mostly carbon). A 3:1 ratio of carbon to nitrogen is ideal.
- Green materials are those that are still living or wet. These are your nitrogen materials. This includes all kitchen scraps, vegetative garden debris, grey water, apples from the field, anything rotting (anything at all), raw manure, weeds, and more. (I prefer to only add young weeds, or those that have not gone to seed. I never add any invasive or aggressive weeds to the compost, especially not those which spread by root).
- Brown materials are those that are dead or quite dry. These are your carbon materials. This includes, dried and crushed leaves, sawdust, hay, straw, cardboard, paper, stalks or thick stems (broccoli, corn, flower stalks that have dried…), and more.
Have ingredients on hand. Always keep a supply of dry carbon materials nearby to the compost, in a separate bin or in a lidded trash barrel.
Shape the pile
If your compost pile is not covered, shaping the pile can help to manage the moisture content. During dry times try for a flat or slightly concave shaped pile. This will collect the water needed to aid in decomposition. During wet times go for a hill-shape to allow excess water to run off.
You do not need to turn your compost until you turn it out of the bin to use in the garden. If the pile is built using the right recipe, all of the critters and worms will do it for you during the decomposition process. One exception is when the pile becomes to wet or anaerobic. Then, a good turn and maybe even a re-stack of the pile may be in order to give it some air. See the troubleshooting section below for more tips.
If you are composting primarily kitchen scraps (and you eat veggies regularly) it should take about a year to fill a bin. Its okay to add to a bin for many years but if you’d like to harvest from your compost you should plan to cap it at some point and start a new one. A capped pile means you stop adding to it in order to allow the compost to ‘finish’.
How do I know when my compost is ready? You will see the contents shrink to 1/3 to 1/2 it’s size as the microorganisms do their work decomposing. When the pile is finished it will stop shrinking. At that point you can turn the pile out of the bin and find finished compost therein. Any remaining brown matter that has not decomposed can be added in to the new pile as brown matter, or use it as mulch on your garden.
Usually, a capped pile can sit undisturbed for 2-3 months during the warm season before turning the entire pile out of the bin.
Sifting compost If there are still remains of carbon material like hay or straw in your otherwise finished compost, sift out the carbon matter that has not yet decomposed. Use it again in the next pile, or use it as mulch in the garden.
Basic Steps for Composting
The recommended steps for building a healthy and active backyard compost pile below are intended for a 4’x 4’x 4’ bin (approximately). There are many easy-to-build design plans available online with a quick search for ‘compost bins’. You don’t need a bin but it will certainly help to contain the pile, to control moisture, and to keep critters out.
1) Start your pile from the bottom up. Start a pile by layering about 12 inches of brown, dry, carbon material spread evenly across the bottom of the pile, edge to edge in a criss-crossed pattern. Hollow stems such as those from cornstalks, garlic stalks, or from perennials such as phlox, sylphium, or jerusalem artichoke work very well. This bottom layer is providing a well-aerated structure for a year’s worth of compost to sit on top of.
2) Create a bio-filter to keep down smells. Layer several inches of hay, or any carbon material, around the perimeter of the pile (like a doughnut), leaving the center bare for your compost deposit (like a doughnut hole). This perimeter hay will act as an insulator and a bio-filter around the edges of the pile aiding to keep the smell down making it less attractive to rodents and other mammals, and more attractive to people! The center of the pile, the ‘doughnut hole’, is the high-activity spot in a compost heap.
3) Make a deposit. Add 6-12 inches of mixed food scraps (nitrogen materials) inside the ‘doughnut hole’ to be level with the perimeter of carbon materials. If the deposit you are adding is very wet, layer in a bit of carbon material to add air space.
4) Cover the pile. Build a top bio-filter by layering 4-6 inches of loose carbon material on top of the deposit, and edge to edge in the bin.
Repeat steps 1-4 until the bin is full. It’s that easy!
Managing the compost heap
A pile may not become very active until it has enough mass. You’ll know when that is by the heat being created in the center of the pile, usually after a few deposits or when the pile is about 2 feet high. At that point you should have an idea of the volume of food scraps produced each week and of how much time you can afford to manage your pile. Having a regular system in place will afford the best results. Here are two systems that work for most people.
Pay as you go composting: This style is for those who make small daily or weekly deposits. Dig into the center of the pile to create a new center hole with each deposit. Using a spade fork, pull the top layer of carbon materials to the sides of the bin revealing a partially decomposed center. Mix those contents in with the carbon matter around the perimeter. Make your deposit. Repeat steps 3-5 in this fashion.
Batch composting: This style is for those who produce a lot of veggie scraps and like to save em’ up for a monthly deposit. Follow the same instructions for ‘pay as you go’ but create a larger center hole for your deposit and have extra carbon materials at the ready to layer in, and to build up the bio-filter around the outer perimeter.
Capping the pile
When the bin is full, cap it with a final 4-6” layer of carbon materials. Leave this finished pile to cure for about 3 months or until it has stopped shrinking. Then, dig in and harvest! The best compost will be at the bottom. If anything is not decomposed, add it to your active pile. Start a new active pile in another bin.
Troubleshooting the Compost Pile
- If your pile is too wet it will stink. Add brown material (carbon) to fix it. Dig into the center of the pile and assess the heat, and moisture content. If the entire pile is cold and very wet you may need to rebuild the pile from scratch to give it proper air circulation. Consider adding a cover to your bin to keep future rain out. Water is necessary for compost but too much will cool it and make it uninhabitable for microorganisms.
- If your pile is too dry it will not be active. Add green materials (nitrogen) to fix it. Dig into the center of the pile and add your nitrogen materials, then cover with some of the carbon materials you just pulled to the side. You may need to water the pile if it has been a very dry period.
- If the activity in your pile seems too slow, sprinkle a very thin layer of soil, or slightly more compost or manure edge to edge before you make a deposit. Healthy soil, compost, and manure are compost activators, containing potentially billions of microorganisms.
- To jump start activity in an old pile, dig in to the center of the pile and add some raw manure and green matter. Cover it back up with carbon materials. You may need to rebuild the pile from scratch to give it proper air circulation.