Environment Recycling & Waste Hot Composting: Step-by-Step Guide By Starre Vartan Writer Columbia University Syracuse University Starre Vartan has been an environmental and science journalist for 15-plus years. She founded an award-winning eco-website and wrote a book on living green. our editorial process Starre Vartan Updated May 31, 2021 Cavan Images / Getty Images Share Twitter Pinterest Email Recycling & Waste Zero Waste Plastics Overview Total Time: 6 - 14 hours Yield: 4-5 gallons of compost Skill Level: Beginner Estimated Cost: $0-200 Hot composting is the process wherein microorganisms and bacteria biodegrade kitchen scraps and yard waste to create a concentrated material that can be used as a soil enricher. Hot composting is a little more complicated than cold composting, as it requires more attention and maintenance, but the upshot is you get compost more quickly— as fast as a month or so. When hot composting, specific temperatures and moisture levels need to be maintained, as does a careful balance between nitrogen, carbon, and oxygen. This is different from cold composting which doesn't need more than very basic monitoring, if any. Using special redworms to break food down into compost is called vermicomposting, and bokashi composting requires special equipment and careful monitoring. While it can take a little time to learn how the process works and tinker with the levels, it's worth remembering that this is a natural process, so you can't really "break" it or do it wrong. If you do mess up levels of moisture or it gets too dry or too hot, your compost will still break down, it will just happen more slowly, more akin to cold compost. You can almost always restart the process as there are always bacteria and microorganisms in the environment to take the place of those that might have gotten accidentally killed. Why Composting Is Good for the Planet It may be surprising, but in most households, 30% of garbage is made up of food scraps and yard waste. Most of this material can be composted—which both saves space in landfills and reduces the greenhouse gas methane, which is produced when food and yard waste break down without oxygen, as in a typical garbage dump. On top of reducing your household waste, you also get a rich material that you can use to fertilize your veggie or flower garden, your potted plants, or even your lawn. Kids and adults alike can learn from composting, too, as it brings attention to food waste in the household and is a practical way to learn about chemistry, microorganisms, and decomposition processes. What Can Be Hot Composted and What Shouldn't Be? Hot composting—like any composting system—needs a combination of materials in order to get enough nitrogen and carbon for the composting process to work. Most compost experts term these two categories as green (nitrogen-rich) and brown (carbon-rich). Green material is the food waste that comes out of your kitchen and includes fruit and veggie peels, eggshells, cooked grains, and coffee or tea grounds, as well as freshly cut grass clippings. Yard waste like dead leaves and shredded newspaper or cardboard is the brown stuff. When you are hot composting, the balance between green and brown materials is very important, and you should be careful to keep the ratio at 2/3 brown material to 1/3 green. For temperatures to get to the level needed in hot composting, the ratio matters. You'll know you are doing it right when your compost gets to the correct temperatures, as detailed below. Except for industrial composting, all other types of compost exclude animal products and fats. This is for two reasons. First, these materials will smell bad, which is not only unpleasant for the person tending the compost pile, it will attract undesirable animals and pests to your compost pile. So skip composting meat, cheese, oils, bones, pet waste, charcoal, ashes, sick or diseased plants, and plants treated with pesticides or herbicides. What to Hot Compost Fruits and veggies, cooked or raw Eggshells Coffee grounds and looseleaf tea Cooked grains without meat, like pasta, rice, quinoa, or oats Beans, lentils, hummus, bean dips Nuts and seeds 100% cotton or 100% wool material (any amount of polyester or nylon won't compost and will be leftover) Hair and fur Fireplace ashes Shredded paper, cardboard, and newspaper Leaf clippings and dead houseplants Yard waste of all kinds including branches, bark, leaves, flowers, grass clippings, and sawdust What You'll Need Equipment 1 Bin or enclosure (optional) 1 Gardening shovel 1 Medium tarp (for a pile if no bin) 1 Compost thermometer 1 Outdoor watering can or hose Ingredients 1/3 part nitrogen-rich (green) material 2/3 parts carbon-rich (brown) material Instructions Hot composting can seem intimidating at first, but remember, this is a natural process. If you mess up, you can try again. Keep in mind that there are four elements you want to keep in balance: nitrogen (green stuff), carbon (brown stuff), oxygen (air), and moisture (water). Choose a Compost Location First, choose a location in your backyard or garden that's convenient to the house, since you will be checking your compost often. Be sure you choose a shady, well-drained area. Locate it away from any structures since insects will be a natural part of the composting process. A hot compost pile needs structure to it. So make or buy a compost bin. To make a quick and easy hot composting container, attach a piece of woven wire fencing or chicken wire to itself at the circumference you'd like for your compost. dimitris_k / Getty Images Whatever you use, it shouldn't be bigger than about 1 cubic yard of volume. That's about 5 feet wide by 5 feet long by about 3 feet tall—it doesn't have to be those exact dimensions but should hold about the same volume. This is to both create a system within which heat can build up and moisture is contained, but that you can also aerate easily. Set Up Your Compost Site So you've found a shady, well-drained site. Now you can put the foundation down for your hot compost. Clear the ground so you have bare earth and place your compost bin or wire containment. Begin at the bottom of the container or enclosure and layer leaves, small branches, dry lawn clippings, newspaper, or torn-up cardboard—to a depth of six inches. This is your brown material and will serve as the bread in the compost sandwich. Make sure to vary the types of material, especially at the bottom of your pile—you don't want anything that mats together, like grass clippings, as your only base material. Lightly water the base. Add Your Green Material For hot compost, you're better off adding larger amounts of green material all at once than smaller amounts more frequently. The ratio is two parts carbon (brown material) to one part nitrogen (green stuff), so you'll want to keep track of how much material you are adding. Add your compost, starting with a thicker layer in the middle and less on the sides, with a maximum of about 5-6 inches. That will be on top of the 6 inches of brown material you have already put down. Layer and Measure Keep going with the layering—if you have saved up enough material, you can do two layers of green material to start, just remember to always end with the brown material on top and keep to the 2/3-to-1/3 ratio. As long as you stick to the types of scraps that can be composted when it comes to your green materials, don't compost things that shouldn't be (see list above), and keep your air and moisture conditions right, your compost won't smell and you won't have to worry about pests or rodents. Maintain Your Compost In order to get your compost to the hot stage, which will lead to a faster and more efficient breakdown of materials, you need to keep it both aerated and moist. After you add your green material and layer the brown on top, lightly water your pile—distribute it evenly, and only to the level that it feels like a well-wrung sponge—it shouldn't be soaking wet or dripping. As you are saving up your kitchen scraps for the next compost layer, which should take a week or so, let the compost sit untouched; it will be naturally accumulating bacteria and microorganisms. Take Your Compost's Temperature After two or three days of starting your hot compost, check its temperature using a compost thermometer. You are aiming for temperatures of between 141 F to 155 F. This is the temperature at which the seeds of weeds and disease pathogens are killed. You don't want it to go too much higher though—160 F and above will kill the bacteria and microorganisms you want to break down the materials in your compost. (If it starts to get too hot, just introduce some air by turning the layers over and aerating it.) Check your compost daily—it should maintain this temperature for a few days to a week. If the pile isn't hot enough, you need to add more nitrogen (that's the green stuff). If the pile smells, add more carbon (brown stuff). Aerate Your Compost When you have enough kitchen scraps saved up, or in about a week, take them out to your compost bin—before you add them, aerate what's been "cooking" thus far. This means turning over those layers you created when you set it up. Then add your scraps, and add another layer of brown stuff on top at the 2/3 to 1/3 ratio. Finish by watering the whole pile—if the lower layers you have just aerated are pretty damp, then just add water enough to dampen the new layers of compost you have added. If you notice that the layers you have turned over are a bit dry, add enough water to ensure the whole pile is moist—remember those microorganisms work best and fastest when they are warm and damp. Harvest Your Compost After 1-3 months (how long depends on how well you've maintained constant conditions in your compost as well as your local weather conditions) you should be ready to harvest your first round of compost. The pile should have noticeably decreased in size even though you were adding layers to it. Overall you will lose a lot of volume—as the materials turn into compost, they will get 70-80% smaller. If you added a gallon of green material each week (so 3-4 gallons of brown), after a month you'll just have a gallon or so of compost. So you may want to wait until month two when you'd have twice that much to harvest it, but that depends on what you're using the compost for. Use Your Compost Christopher Hopefitch / Getty Images Your compost will be at the bottom of your pile—it will be a dark brown, crumbly material that smells pleasant and damp. There shouldn't be any recognizable pieces of what you composted left behind. You can add a couple of cups of compost for repotting houseplants (about 1/8-1/4 of the volume can be compost mixed with soil), or mix it 50/50 with potting soil when starting seeds. Add compost directly to the soil of a garden bed or container (for veggies of flowers) in the spring or after harvest in the fall. You can add it to the soil when planting trees and shrubs You can even use compost on your lawn in the spring or fall. You can simply sprinkle it over your lawn; aim for an amount between 1/8 and 1/4 of an inch thick. Frequently Asked Questions If I make my compost hotter, will it degrade material faster? No, if your compost gets too hot (above 160 degrees Fahrenheit) it will kill the bacteria and microorganisms that do the important work of breaking down your compost. A too-hot compost will actually take longer to degrade. How can I make my hot compost degrade material faster? Three things can help accelerate your compost. The first is chopping your compost (both brown and green stuff) up into smaller pieces—with your kitchen scraps you can do this with a knife, and with the brown stuff you could run a lawnmower over leaves or small branches to chop them up. The second accelerator is adding animal manure to your compost. You only want to do this once you get the hang of composting, because it's important that your compost get hot enough to kill pathogens. But if you are at this stage, you can add fresh chicken, cow, horse or goat manure as a layer in addition to your browns and greens. You can also add a compost booster to your pile. Add 1/4 cup molasses and a packet of yeast to a 5-gallon bucket along with a couple of shovel-fulls of soil. Add warm water to within a few inches of the top of the bucket, stir, and leave in the sunshine for a day or two. Then, pour this mixture into your compost pile. Do I need to cover my hot compost pile? If it's very rainy where you live, or you have a rainy season, you should cover your compost during that time period with a tarp or a cover if your bin came with one. If your compost gets too saturated with rain, it will become too soggy to degrade efficiently.