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How to Compost: Hot and Cold Methods

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Did you know that there are "hot" and "cold" methods of composting? Read on to learn more.

Composting is a method of recycling naturally decomposing matter. Ingredients, size of the pile, local weather conditions, and your maintenance habits will affect the outcome. Note that shredded leaves, chipped wood, and chopped food scraps generally decompose more quickly than whole or large pieces.

Hot, or Active Composting

The quickest way to produce rich garden humus is to create a hot, or active, compost pile. It is called “hot” because it can reach an internal temperature of 160°F (140°F is best) and “active” because it destroys, essentially by cooking, weed seeds and disease-causing organisms. The size of the pile, the ingredients, and their arrangements in layers are key to reaching that desired outcome.

Size: A hot compost pile should be a 3-foot cube, at minimum; a 4-foot cube is preferred. The pile will shrink as the ingredients decompose.

Ingredients:

  • One part high-carbon materials (shredded, dry plant matter such as leaves, twigs, woody stems, corn cobs)
  • One part high-nitrogen green plant matter (green plant and vegetable refuse, grass clippings, weeds, trimmings, kitchen scraps—but avoid meat, dairy, and fat) and good-quality soil

Pile the ingredients like a layer cake, with 2 to 4 carbon materials on the bottom (twigs and woody stems here will help air to circulate into the pile). Next, add a layer of soil. Add 2 to 4 inches of nitrogen-based materials, followed by soil. Repeat until the pile reaches 2 to 3 feet high.

Soak the pile at its start and water periodically; its consistency should be that of a damp sponge.

Add air to the interior of the pile by punching holes in its sides or by pushing 1- to 2-foot lengths of pipe into it.

Check the temperature of the pile with a compost thermometer or an old kitchen thermometer. A temperature of 110°F to 140°F is desirable. If you have no heat or insufficient heat, add nitrogen in the form of soft green ingredients or organic fertilizer.

If a foul odor emanates from the pile, flip the compost to introduce more air. And consider: Did you add meat or dairy products? Remove and discard them, if possible.

Once a week, or as soon as the center starts to cool down, turn the pile. Move materials from the center of the pile to the outside. (For usable compost in 1 to 3 months, turn it every other week; for finished compost within a month, turn it every couple of days.)

Cold, or Passive Composting

Cold, or passive, composting uses many of the same type of ingredients as hot composting and requires less effort from the gardener, yet the decomposition takes substantially longer—a year or more.

To cold compost, pile organic materials (leaves, grass clippings, soil, manures—but avoid dog, cat, and human waste) as you find or accumulate them. Bury kitchen scraps in the center of the pile to deter insects and animals. Avoid adding meat, dairy, and fat. Also avoid weeds; cold compost piles do not reach high temperatures and do not kill weed seeds. (In fact, weeds may germinate in a cold pile.)

Compostable Goods

In addition to the ingredients mentioned above, any of these items may be added to a compost pile:

  • Coffee grounds and tea bags
  • Dry goods (crackers, flour, spices)
  • Eggshells
  • Hair
  • Nutshells
  • Pasta (cooked or uncooked)
  • Seaweed
  • Shredded paper/newspaper

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Comments

I am new to this as well, so

By Pvonwist

I am new to this as well, so a few questions about hot composting?

Once I have built up my 3 foot compost lasagna can I keep adding to it or other than turning it, do I just leave it alone?

Just wondering how to hot compost during the winter. Can I build my 3 foot compost lasagna and just continually add to it over the winter and keep turning it?

I am assuming a couple 4x4x4 boxes are necessary and rotated through over the growing season?

Lastly, would it be advisable to have a plexiglass/glass/plastic lid over top of the compost bin to help cook the compost over the winter?

Hi there -- Here are some

By Almanac Staff

Hi there -- Here are some answers to your questions. Starting with the last question:
A cover will certainly help keep the soil slightly warmer, which is beneficial when you come to plant into it in spring, and will stop it from getting too wet, but you may need to check it occasionally and water it if it’s very dry.

Boxes aren’t essential for

By Almanac Staff

Boxes aren’t essential for lasagna gardening or for composting; it depends on how tidy you want your garden to look! Bins for composting (the larger, the better) can help the compost to heat up better than an open pile, and are less of a draw for rodents. If creating a lasagne bed inside a raised bed, plant into it just as you would into the open ground -- you will probably need to add some finished compost or good soil for plants to get started though.

During the winter composting

By Almanac Staff

During the winter composting slows down dramatically -- depending on your climate there may be no noticeable changes in your compost over the winter. Turning it will introduce air into it and cool it further. 

Lasagna beds are designed not

By Almanac Staff

Lasagna beds are designed not to be turned -- they’re a form of no-dig gardening. Composting materials are added in layers -- like in a lasagna -- and not mixed together.  They rot naturally and worms and other soil micro-organisms do the mixing. Add as much as you need to create the bed but remember it will sink as the materials rot.

When composting in a bin (rather than piling composting ingredients where you will be planting) you can keep adding material until the bin is full and then leave it to rot - it’s a good idea to have an extra bin or two that you can turn to when the first is full. Composting is a slow process and may take anything from six months to two years depending on many variables such as your climate, the weather, and the materials you’re adding to the bin. In my experience it usually takes around a year. Mixing in grass clippings (not too much though, and not in thick layers) does speed things up a little.

Thank you! I am new at this

By Jackie S Colicci

Thank you! I am new at this and was wondering if there are any suggestions on containers or building materails used for hot composting.

You do not need a bin or

By Almanac Staff

You do not need a bin or container to make compost. Piles work well. However, if you'd like a bin, to keep it tidy, it needs to be big enough to hold heat. A pile that begins with about one cubic yard of material is big enough for year-round composting, even where winters are cold. That means a bin about three feet wide, three feet high and three feet deep will be big enough to retain heat. If you Google, "Hot Compost Bin," you'll see some options.

You can get compost and

By nature farmer

You can get compost and animal feed at the same time using bsfl (black soldier fly larva). They turn your compost for you, devour all types of organic material including meats and dairy, and are used for feed(chickens go nuts for them). Quickest time I've clocked is table scraps to complete compost in 5 days

Do you use them in the "hot

By NewSarah

Do you use them in the "hot compost"? I'm a newby to all compost/gardening & want to be efficient :)

Thanks for the interesting

By Regina Dabbs

Thanks for the interesting article! I started 'growing my own dirt' last year, and love this earth friendly activity. Good hints here!

I nurture my compost bins

By Jane Umstead.

I nurture my compost bins year 'round. (Amherst, VA) Yesterday, I tilled in some beautiful new soil as I put my veggie garden to bed for the winter. Not only does it help my soil, I also get some interesting volunteers in my garden!

Thank you for teaching me a

By Pleasantstorm

Thank you for teaching me a little bit more about my own compost pile!
Your Friend,
Stormy

thank you for the good

By patsween

thank you for the good article on composting,I have always wanted to do this and now I know how.

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