The Heat is On: Hot Composting Makes Fertilizer Faster

For most people, gardening is a leisurely pursuit, a respite from today’s mile-a-minute world.

But even the most patient gardener has probably looked longingly at those carefully sown rows of seeds or those newly budding plants and thought, what is taking you so long?!

While there’s generally no rushing Mother Nature, we can speed up the production of at least one thing, and that’s the nutrient-rich fertilizer coming out of our compost bins.   

The secret is to turn up the heat on the microorganisms responsible for decomposing yard waste and kitchen scraps. This is accomplished through a method aptly called hot composting.

Hot composting aims to create an environment where temperatures reach between 130° and 140° Fahrenheit. Under those conditions, hot composting can produce finished compost in about three to four weeks, a fraction of the time it takes traditional composting to do its thing. 

That means you’ll more quickly enjoy all the soil-improving and plant-growth-boosting benefits that compost brings to your garden — and you won’t break a sweat doing it.  

Some like it hot 

Despite its presto-change-o results, there’s no real magic to hot composting. Instead, it comes down to basic science and creating the kind of environment hardworking microorganisms like best. 

The fact is, bacteria, fungi, and actinomycetes (microbial fungi-lookalikes) all thrive under hot temperatures. Fostering the right ecosystem for them in your compost bin amps up their activity levels. And the more the decomposers do, the more energy they release as heat, leading to a cycle of increased productivity and more rapid breakdown of organic materials. 

Faster compost production may be the key reason to try hot composting, but it’s not the only one.

High temperatures also eliminate the weed seeds that enter the compost bin in yard waste. And while most of the bacteria in your compost bin are helpful, some aren’t. Heat kills off the harmful kind, banishing bad odors in the process. 

The right stuff 

Like many things in nature, hot composting is all about balance. In this case, it’s finding the right proportion of “brown” and “green” materials for your compost bin or pile.

• Brown materials are carbon-rich, providing structure and aeration for your bin. They include dry leaves, straw, and shredded cardboard. 
• Green materials are things like coffee grounds, food scraps, and fresh grass clippings, which feed the microorganisms. By food scraps, though, we don’t mean emptying what’s left on your dinner plate into your compost pile.  You never want to include meat, dairy products, or oily food waste, which can attract pests and create odors.

Moisture is also a factor in hot composting. Your compost bin should be moist but not soggy. Some gardeners say the right level of moisture feels like a wrung-out sponge. 

Finally, you need to turn the pile every other day or so (ok, that might require a little sweat on your part) to aerate it. Most microorganisms in a compost pile are aerobic, meaning they require oxygen to function.

When there’s not enough oxygen, the pile becomes anaerobic. Anaerobic microorganisms will still produce compost, but it will take longer. And because this kind of decomposer produces byproducts such as methane, your bin or pile will smell bad.

Hot composting 101

Ready to give hot composting a try?

Here’s how to get started:

• Choose a premade plastic or wood hot composter or build your own. If you live in a colder climate, your composter must be insulated to maintain heat. Wherever you are, make sure your hot composter is well-ventilated.
• Find the right location. To maintain the heat, hot composting requires more space than traditional composting. Choose a level, well-drained area in your yard that gets indirect sun most of the day. Avoid locations where the bin will be exposed to harsh afternoon sun; excessive temperatures can harm the beneficial organisms. 
• Start with a base layer of brown materials, about 4 to 6 inches deep.
• Add a layer of green materials, about 2 to 3 inches thick.
• Alternate brown and green materials, two parts brown to one part green.
• Add enough water to achieve that wrung-out sponge moisture level.  

To maintain your hot composter:

• Use a compost thermometer to take your hot composter’s internal temperature every couple of days. Remember, 130° to 140° degrees is ideal.
• Turn the pile every other day or so.
• Add water if the pile feels dry. Overdone it? Add more brown material to absorb the excess.
• Add new green and brown materials as the pile shrinks.

In a month or so, your compost will be dark and crumbly with a nice, earthy smell. It’s ready to go in your flower and vegetable beds, your plant pots, and even on your lawn — maybe even heating up a little friendly competition with your neighbors who is the best gardener on the block.