Vermiculture & Greenhouse Gas Emissions

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!



Hi Joshua,

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!
😎

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Comments

    • GA
    • September 10, 2014

    While I’m sure the sources on this have done real research, I think it all sort of ‘misses the point.’

    The benefits of worm (and other types of composting) go well beyond what happens during composting. You already referred to diverting from landfill. The end-use – to use as soil supplement that replaces stuff that would be bought/produced/transported – is another. Healthier soil is also a major benefit – that in various ways likely reduces bad runoffs to waterways. Etc, etc.

    And finally, for the major factor specific to worm composting: it allows/encourages people who might not otherwise compost to get the benefits above. People can (and do!) do it indoors or in apartments, diverting stuff from the waste stream (with associated costs) that would not be possible without it. (Or simply because some people like composting when they do it with worms)

    So studying the exact amount of methane, NO2, is missing the point. It’s like doing a detailed analysis of which kind of bike gear results in the rider putting out less CO2, or energy efficiency of the bike light, when the major advantage is that a biker is not behind the wheel of a car.

    • Mark from Kansas
    • September 10, 2014

    This is an excellent article and brings to light the many benefits of worm composting. There was a time when my family would put kitchen waste down the disposal. I believe this puts a further burden on our waste water treatment plants. I now put our kitchen waste in my Worm Inn that I purchased. In my opinion, the Worm Inn was the best investment I’ve made toward my vermicomposting.
    As GA points out, even a small apartment worm bin can make a huge difference.

    • GA
    • September 10, 2014

    I had a follow-up thought from another angle on the above – what it makes sense to consider and compare with. I’ve composted grass clippings and I’m sure it produces more methane, nitrogen, etc – or at least I smell it, I have no data.

    Figured out a while back that leaving the grass clippings on the yard was better for the yard, better for the compost pile, and better for my back (’cause I no longer have to turn the stinky mess that always seems to result). I’m no grass fanatic (in terms of having a perfect lawn), but the cut/mulched grass disappears quite quickly to the eye – if any clumps bother me, I make an extra pass to mulch some more. The only exception to this is when I pick up leaves to mulch and compost, and grass clippings get in there too.

    So the grass sort of disappears on its own. But you can see and feel the organic matter if you get down and look closely. It becomes a sort of thatch around the grass, but part of the grass. Seems to help keep water levels/moisture about right. The lawn doesn’t seem to ever need fertiliser (well, maybe around some very, very thirsty trees, where I just add soil supplements and vermicompost).

    So to circle back to the original discussion: I think the amount of greenhouse gases, methane and nitrogen etc _would_ be relevant in talking about composting grass clippings. But mostly because it is a silly step that could and should be skipped, and if done, I’d have to do more work, get more fertilisers, etc., and that would be the waste.

    • Joshua
    • September 23, 2014

    My apologies for the seriously delayed response, it’s been a chaotic two weeks. Thank you for the detailed and multi angled response, I truly enjoyed the bike analogy. I agree that focusing on the GHG quantity diverts the conversation away from the vast benefits. My inquiry was simply a light bulb moment while I was working my worm bin, for which I had to find an answer. I strive to make a conscious effort to have as little a negative impact on our environment as I can and had a similar visceral response to the idea that possibly, just possibly vermicomposting was not as effective at addressing our copious amounts of organic waste as I had believed. With this introduction to Dr. Edwards I have begun to nerd out on his research. Thank you again for the insightful and entertaining response!

    • GA
    • September 29, 2014

    Joshua, thank you – I will read that. I definitely meet the lazy criterion, one reason why I do it this way.

    And I think your question about greenhouse gases is totally reasonable. To use another old analogy or saying though, ‘the perfect is the enemy of the good.’ Maybe there is a slightly better way somewhere to compost or use foodstuffs to avoid greenhouse gas emissions – but the ‘good’ way that people actually use and is practical can be a big improvement.

    • GA
    • September 29, 2014

    Darn, I started writing and forgot my point. The exception I make in lawn care is removing leaves. Which I do by just lawnmowing with the bag attachment (the only time I do this). Done right, it mulches the leaves with a bit of grass. Piled up it heats and composts for a bit with really interesting white rot – water may need to be added – and when it cools worms will love it. Creates a great compost.

    A contact suggested sticking toilet paper or paper towel rolls (after the tp is gone of course) vertically in these piles to allow for air flow / keep the pile from going anaerobic (I also turn it once in a while, but not often). I don’t know if it helps, but during the ‘hot’ phase, it almost looks like smoke coming out of the tube (I think it’s just steam).

    • Joshua
    • September 29, 2014

    I could not agree more about perfection. Even if a more efficient way existed, the enjoyment factor with the worms would make leaving vermicomposting rather tough.

    I will have to give the TP roll suggestion a go. Tis the season for leaves to collect on the ground so what better time to play with it. One of my friends that also raises worms use leaf material dogmatically and swears by the difference in the finished castings. I plan to mix some in this season as I didn’t have the foresight to save them last year and will have to try running them over with the lawn mower (was eye-balling a leaf mulcher) and save the $100 or so dollar for another project. How long do allow the leaf mixture to compost before adding it to your system?

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