Compost Slow? Science Says It Doesn’t Matter!

If your compost doesn’t get hot, don’t despair! 

A new study suggests that longer, cooler composting periods can create compost as good as compost produced at full heat levels. 

That said, there are several things you need to be aware of to achieve quality. The good thing is none of them require much extra effort. 

Industrial composting relies on short heat cycles to produce compost quickly and at scale. 

In contrast, home composting benefits from a longer, more natural decomposition process.  This can result in better nutrient retention, higher microbial diversity, and improved soil health.

The authors highlighted current concerns over home composting: that the lack of heat doesn’t kill pathogens, weed seeds can survive and that compost could be contaminated. 

However, when they dug into the problem, they found that many of the concerns were unfounded. 

Let’s dig into each point one by one.

Industrial composting uses temperatures of 55-70°C (131-158°F.) to increase the speed of decomposition. 

However, the researchers found that home composters who can’t reach these temperatures can achieve the same results over a longer time period. 

This longer time period has benefits too.

Research demonstrates that compost matured over 6-12 months has a higher microbial diversity leading to better nutrient cycling and soil benefits.

Another concern is over pathogens.

The researchers agreed that these can persist for longer in cooler conditions. However,  they found that over time pathogens decline naturally over time as other microbes compete for resources. 

This isn’t new, by the way – there’s a whole host of ways in which composting kills pathogens over time. See our article and infographic The Pathogen-Destroying Power of Composting for a fascinating insight into this. 

As a home composter, you have complete control over what’s in your compost. 

Perhaps because of this, the researchers found that home made compost had a very low level of unsuitable ingredients (such as plastic or glass) and low levels of heavy metals. 

What’s more, they found that the slower breakdown of compost led to a more complete breakdown of organic matter, leading to a nutrient rich compost. 

The super-hot composting approach used by professional composters can kill many of the beneficial microbes in compost. 

In contrast, a slower, longer composting procedure also supports a wider variety of bacteria, fungi, and beneficial organisms which add more value to the soil. 

What’s more, worms and insects thrive in compost heaps, and in the process add additional nutrients. 

I can attest to the value of worm castings, as I’ve had fantastic results using vermicompost. 

The authors argued that by following basic composting principles such as:

• aerating the compost
• monitoring moisture levels
• allow the compost enough time to mature

you can easily achieve high quality compost that will benefit your garden for years to come. 

So if you’ve worried that your rough compost is not good enough for your garden – don’t.

While you may need a bit of patience, the combination of extra time and the diverse materials mean you can create a compost that is exceptionally rich and beneficial for your soil.

Read more

Why Homemade Compost is (Usually) Better Than Store-Bought Compost

Niekraś, L., Rombel-Bryzek, A., & Moliszewska, E. B. (2024). Home composting – rules, conditions, new solutions. Chem Didact Ecol Metrol, 29(1-2), 95-110. https://doi.org/10.2478/cdem-2024-0007