Hot Composting vs. Cold Composting: 2 Easy Compost Methods

Hot composting vs. cold composting… what’s the difference? When most gardeners think of composting, they think of hot composting: that pile of organic matter in your yard that is turned and maintained regularly. And it’s no wonder that hot composting has earned the reputation of being the method of choice for many. It is the quickest way to produce a large volume of compost.

How to Hot Compost

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Hot compost relies on moisture, aeration and a specific ratio of nitrogen-rich to carbon-rich organic matter. Hot compost piles are ideally 4’ square. They are formed by layering three parts carbon-rich material (dried leaves, sawdust, shredded paper and straw) to one part nitrogen-rich material (fresh weeds and grass clippings, kitchen scraps, eggshells and coffee grounds).

For quicker results, items should all be added at once and the pile should be regularly watered to maintain the moisture level of a wrung sponge. Many gardeners opt to build hot compost heaps in sunny areas of their gardens and within easy reach of a watering source to maintain proper temperature and moisture levels. Hot compost piles can be mounded together naturally or contained within homemade bins made of upcycled pallets or chicken wire.

The real work with the hot compost method begins with aeration. Hot compost needs to be turned regularly to maintain optimal conditions for the microbes, fungi and bacteria that decompose food scraps and yard waste. With the help of a compost thermometer, temperature should be monitored every day or two to determine when your pile should be turned. An optimal temperature for hot composting is between 141 and 155°F. Temperatures below or above this range signify that a pile should be turned so microbes remain active and are not killed by overheating.

Premade compost tumblers can be purchased to make turning your pile easier; however, these only work with smaller volumes.

Though hot composting may take a bit more work, it makes up for it by producing a finished product in as little as four weeks.

How Do You Know When Your Hot Compost is Done?

When your hot compost is finished processing, the core temperature of the pile will drop, and you’ll be left with a rich, earthy-smelling compost ready for garden use. Even better, due to the heat produced by this method, most weed seeds and plant pathogens will be killed resulting in a pest-free final product.

Hot Composting vs. Cold Composting

While hot composting takes an active approach, cold composting, a closely related method, is more passive.

Like hot compost, cold compost piles are kept moist and are formed by a ratio of three parts carbon-rich materials to one part nitrogen-rich material. The similarities, however, end there. Cold composting does not need to be turned, although doing so will produce results faster. Additionally, waste matter does not need to be added all at once but can be incorporated slowly, as it becomes available.

A drawback of this method is that, because no heat is generated, compost can take over a year to finish. It may still have weed seeds and plant pathogens present.

How to Cold Compost

Cold composting can be as simple or complex as you would like it to be. Cold compost bins can be homemade or bought online to deter pests. Conversely, organic matter can simply be heaped in a pile and left to process on its own. You can opt to turn your pile or not. Either way, you’ll eventually end up with a quality compost.

Some gardeners choose to use a specific type of cold composting, known as “trench composting.” With trench composting, food and yard scraps are dug directly into your garden or near the roots of established plants. The plants are slowly fed as the scraps decompose. This is particularly useful as waste scraps only need to be handled once and can be added directly to specific plants as needed. If you opt to try this technique, be sure to bury food waste at least 10-12” deep to discourage scavengers.

Both hot and cold composting are ideal for processing vegetable and plant matter. Meat, dairy and pet waste (excepting chicken or rabbit manure), however, should not be composted. Additionally, if you live in a cooler climate, both methods will stop working when temperatures drop below freezing. For these reasons, both hot and cold composting work best when combined with a secondary method, such as bokashi or vermicomposting.

Composting is an amazing way to reduce waste, improve your soil and grow the most beautiful garden around!