Interesting question from Joshua:
My name is Joshua and I have been playing with worm composting now for a year, have build a flow through system and am very much in love with what these little guys can do. Your site has been pivotal in my success thus far, so I turn to you with a perplexing question. While the belief that traditional composting is considered a “green” practice, and is without a doubt far superior to sending organic matter to the landfill, it does create a surprising amount of methane and GHG. It made me wonder if processing that same organic material with worms instead would retain the currently trapped carbon in the same way micro and macro nutrients pass through the worms undigested. Have you encountered any research or discussion of this being tested that you could share? Thank you for sharing your passion and have a wonderful night!
You are right about traditional composting being known to release potent greenhouse gases, such as methane (CH3) and nitrous oxide (N2O). What’s interesting, though, is that vermicomposting actually came under scrutiny a number of years ago for having the potential to release a fair amount of N2O as well! Unfortunately the media kind of ran with it, publishing articles with headlines like “Worms are Killing the Planet” in various prominent newspapers, journals etc – and not too surprisingly, things got a bit out of hand.
Thankfully, Dr Clive Edwards (prominent vermicomposting researcher for many years) stepped in and shared his thoughts on the situation, writing an article for BioCycle: “Can Earthworms Harm the Planet?“. I did my own write-up here on the blog as well: “Do Earthworms Contribute to Global Warming?“.
All the fuss basically stemmed from some research conducted by Dr. Jim Frederickson at The Open University in the United Kingdom (and some subsequent interviews he did with the media). Having reviewed Dr. Fredrickson’s research papers, Dr. Edwards felt there were definitely some flaws in the methodology. Here is a blurb from my blog post:
Apart from the sloppy science involved, Edwards also points out that (according to ‘Trends in Greenhouse Gaseous Emissions’, 2006), ALL forms of composting only contribute 0.5% to the total global greenhouse gas emissions!
One of the major issues with the research, as claimed by Edwards, was the lack consideration given to moisture content, which can be a very important factor affecting N20 emissions.
Another serious flaw came in the form of a claim by Fredrickson (to support his own assertions) that German scientists had discovered that worms were responsible for 1/3 of the N20 released when present in a composting system. As Edwards points out, the studies being referred to were actually examining worms in garden soil systems (small laboratory ones at that) NOT vermicomposting beds!
Edwards finishes the article beautifully by referring to multiple studies that have suggested that worms either do not affect N20 emissions at all, or in fact seem to bring about a decrease in emissions of this greenhouse gas!
As touched on, this all happened a number of years ago. Revisiting the topic now (thanks to your email), I was curious to see if there has been any additional research findings in recent years. The only thing I could find (keep in mind, I didn’t do any sort of in-depth literature review) was an article published by Australian researchers, referring to an examination of GHG emissions from 3 common household waste processing systems: 1) backyard composting bins, 2) anaerobic “composting bins”, and 3) vermicomposting systems. What’s interesting (and a bit funny) is that the vermicomposting systems had the LOWEST N2O emissions of the 3! They did, however, have higher methane emissions than the regular backyard composters (but about half that of the anaerobic bin) – but my hunch is that this related more to how the systems were maintained, than anything relating to the worms themselves.
Here is a blurb from the article’s conclusion:
The GHG emissions generally increased with increasing temperature and/or moisture content. This indicates the importance of proper maintenance of the bins to minimise GHG emissions. Overall, vermicomposting provides more stable and favourable composting conditions than the other two systems
Here is a link to the full research paper if you want to check it out for yourself: Emission of greenhouse gases from home aerobic composting, anaerobic digestion and vermicomposting of household wastes in Brisbane (Australia)
Just the abstract (summary) can be found >>HERE<<
I’m a wee bit biased (who ME?! lol), but I’m tending to side with Dr. Edwards and the authors of the other research paper I just mentioned. It’s safe to say that properly maintained vermicomposting systems offer FAR more benefits than hazards for the environment!