Cold Composting (Everything You Need to Know )

cold composting

Cold composting’s claim to fame is that it’s the most straightforward method for transforming organic waste into compost. 

This method doesn’t need much prep work, a watchful eye, or regular turning, making it a top pick for beginners. 

Its perks are clear, but are there downsides to cold composting? 

I’ll answer all your questions about this carefree composting method. 

What Is Cold Composting?

Cold composting is an anaerobic process where microorganisms that don’t need oxygen break down organic wastes via fermentation. This is the easiest composting method, requiring low to no maintenance. However, it’s a slow process that takes a year or two to produce finished compost. 

Cold composting doesn’t ask for much from you. The composting microorganisms will keep going even if all you do is give them your garden and food wastes now and then. 

Although you should expect to get out what you put in!

There’s a trade-off for leaving the decomposition process to these microorganisms to tackle on their own.

You have to wait months and months for your compost.

If you want to take it easy while nature does the composting and you’re happy to give your soil supplement time to develop, cold composting might be right for you. 

Here’s a deeper look at cold composting and what you need to know to get started. 

what is cold composting

Cold Composting Temperatures 

Since you don’t manage the cold composting process, you’re not in control of the temperatures the compost reaches. The air temperature and composting microorganisms influence how hot the compost becomes. 

Compost’s temperatures are higher in warmer regions and seasons. This is because composting microorganisms are pretty fussy about temperatures. They’re like Goldilocks, wanting it to be not too hot, not too cold, but just right. 

Different types of microorganisms grow and work best at different temperatures. As they work, the organisms release heat, slightly raising the compost’s temperature. 

Cold composting microorganisms tend to go all out at two temperature ranges: 50 to 70°F (10 – 21°C) and 70 to 90°F (21-32°C). These aren’t exactly cold temperatures, but they’re cooler than those of the other primary composting method, “hot composting.” Hot composting temperatures can soar to 160°F! 

There are four stages of cold composting, each with a different team of composting microorganisms. The stages are hydrolysis, acidogenesis, acetogenesis, and methanogenesis.

stages of cold composting

Stage 1: Hydrolysis

During this first stage, hydrolytic bacteria get the decomposition going. They release enzymes to break down carbs, proteins, and fats in organic wastes into the simpler molecules of sugars, amino acids, and fatty acids. 

Stage 2: Acidogenesis

In the next stage, fermentative bacteria take over. They continue where the hydrolytic bacteria left off by breaking down the sugars, amino acids, and fatty acids into even simpler molecules. 

Stage 3: Acetogenesis

Acetogenic bacteria do the work during the third stage. They further break down the molecules in organic wastes, producing gasses like hydrogen and carbon dioxide. 

Stage 4: Methanogenesis

During this final stage, methanogenic bacteria finish breaking down the organic wastes, releasing methane gas, carbon dioxide, and traces of hydrogen sulfide. 

I know what you’re thinking: all those gasses must create a stink! Yep, a rotten egg smell is another downside of cold composting. 

What Is The Difference Between Hot And Cold Composting? 

The most significant differences between hot and cold composting are that hot composting is a fast, high-maintenance method, whereas cold composting is an easy, slow method. 

During hot composting, oxygen-needing microorganisms use heat to break down organic wastes. Therefore, you need to diligently monitor and manage this process to keep things fired up. 

On the flip side, during cold composting, microorganisms that don’t need oxygen to survive slowly ferment organic wastes. So you don’t have to stress about monitoring or managing this process. 

See a complete comparison between these popular composting methods.

Does Cold Composting Work?

Cold composting does what you want it to do: break down organic wastes into a rich soil supplement for nourishing your garden. However, it works slowly. 

Is Cold Compost Safe?

Certain organic wastes can make cold compost a safety hazard for you and your plants. These cold composting no-nos include diseased plants, plants treated with pesticides, meat and dairy scraps, pet poop, and weeds and their seeds. 

Cold compost doesn’t get hot enough to kill harmful organisms in sick plants, poop, and animal-based food scraps. Temperatures also aren’t high enough to kill weeds and their seeds. So, keep these wastes out of your cold compost pile.

Another potential difficulty is that cold compost’s odors can attract disease-spreading critters like rats and flies to your garden. Read my rat-proof compost guide!

How Long Does Cold Composting Take? 

Cold composting takes about a year to create finished compost you can use in your garden. Although, you might need to wait double this time for your soil supplement, depending on several factors.

The causes that can make cold composting slower include:

  • Cold weather
  • Large chunks of organic waste
  • Too many browns (carbon-rich organic wastes like fall leaves) in the compost 

How To Speed Up Cold Composting 

You can speed up the process if you’re up for taking on some composting work. 

Here are ways you can make cold composting faster:

  • Keep water levels healthy. Grab a few (gloved!) handfuls of compost and squeeze. Ideal water levels are similar to those of a wrung-out sponge. Sprinkle water on the compost if it’s too dry. 
  • Raise the temperature. Cover your compost with a tarp to warm it up. (Amazon)
  • Go for greens. If your compost is pretty much only browns, add some greens (nitrogen-rich wastes like fruit and veg scraps) or a dose of nitrogen-containing fertilizer. 
  • Get shredding. Chop, break or shred large organic wastes before adding them to the compost. 
  • Mix things up. Turn the compost every month or so. 

How To Cold Compost 

Cold composting doesn’t have strict rules you must follow to get it right. 

There are many different ways to cold compost, but all methods let nature lead. With little to no help from you, organic wastes are free to decompose in their own time, like they would if you weren’t around. 

Cold Composting Methods

Cold composting methods include burying your organic wastes underground and trapping fall leaves in black plastic bags to building a compost heap on the ground or in a bin.

Cold composting on the ground or in a bin are good places to start. Take note of these cold composting basics: 

  • Start your compost with a layer of browns like corn cobs, dry leaves and grass, and twigs. 
  • Throw in your organic wastes as you make them. You don’t have to balance your greens and browns in cold composting, but it’ll help if you have more browns than greens. 
  • Aim to always have a layer of browns at the top. 
  • You might eventually want to stop adding new organic wastes to the compost to let the partly decomposed wastes thoroughly break down and become garden-ready. 

Here are more tips for cold composting in a bin or pile on the ground. 

Cold Composting Bin

There are advantages to cold composting in a bin. Bins keep compost tidy, they’re a good option if space is limited, and lidded containers keep smells in and troublesome critters and insects out. 

Bigger bins tend to be more efficient. So go for something like this large capacity 80-gallon model (Amazon).

Cold Compost Pile Method

If space isn’t an issue and you like the idea of a free method you can start right away, you could try cold composting on the ground. 

Beware: Open piles are more likely to get pests’ attention. To stop your compost pile from becoming a buffet for rats and raccoons, consider composting only garden waste in an open pile or hiding fruit and veggie scraps deep inside. 

How To Maintain A Cold Compost Pile

What makes cold composting shine is that it needs little to zero maintenance. 

Check your compost’s moisture levels every so often. Then, turn it over if you want to show it some love. The decomposition should continue slowly but steadily!

Happy composting 🙂

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