Does Particle Size Make a Difference?

It’s official – 9 out of 10 Babies Prefer Smaller Particle Size!


Something I’ve been meaning to test out for quite some time is whether or not food particle size has a major impact on the growth/reproduction of Red Worms, and just generally on the overall effectiveness of a vermicomposting system. I think it’s fairly safe to assume that foods that are chopped up finely will become “worm-friendly” (much?) more quickly than those that aren’t. After all, there is greatly increased surface area for microbial invasion, so these materials will tend to break down more quickly. But will this translate into much faster growth?

I need to dig up the source, but I recall coming across some research findings that seemed to suggest that smaller food particle size can have a dramatic impact on worm growth rates. I’ve certainly seen a big difference in the overall efficiency of systems receiving waste materials that have been chopped up etc – but I’ve never really done an actual comparison.

This is going to be a pretty simple experiment, but I’m hopeful it will end up being really interesting! As you can see, I am using carrots as the “food” material. I need consistency here, and don’t want to spend all my time trying to create equal mixes of different foods. Carrots are fairly inexpensive (and readily available), and I think they should provide the worms with enough nutrition when mixed with shredded cardboard bedding.

Yesterday I processed a 3 lb bag of carrots for my initial set-up. My “coarse” grade treatment will receive carrots that have simply been chopped into small disks (middle one in above photo) – this will certainly be a vast improvement over tossing a whole carrot in the bin, but should still be quite a bit more resistant than the other two. My middle treatment bin will receive carrots that have been cut up with a peeler – so basically carrot ribbons. My “fine” grade treatment will receive carrots that have been finely chopped and then further pulverized. It’s important to mention that all of these chopped up carrots (for all treatments) will be frozen prior to use. This will further aid the breakdown process – and will make it easier for me to pulverize the fine-particulate carrots prior to adding them to the bin.

As you might imagine, I will be adding equal weights of carrots to each treatment when I set up the bins and each time I feed. Not 100% sure how many worms I’ll be adding to each, but my plan is to use immature worms that are similar in size (and of course, will add the same number to each bin). This way I know the worms weren’t already fertilized (carrying sperm) when added.

The carrots are in the freezer now. Will likely take them out today and aim to get the bins set up tomorrow. Next week I will add the worms!

Stay tuned!

Afterthought – I guess technically my “ribbon” treatment won’t be receiving smaller particles than the coarse grade treatment. Perhaps “surface area” (degradability? lol) would be a more relevant parameter here.

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    • Terri
    • September 1, 2011

    This will be good info for those who are interested in raising worms for commercial purposes.
    As for me, a home composter with time at a premium, I’m perfectly OK with things going a bit slower in the worm bin. I don’t have time to chop everything up. It’ll get there eventually. 🙂

    • Bentley
    • September 1, 2011

    Hi Terri,
    I think it will be interesting even for those not involved in commercial vermicomposting enterprises (I hope – haha!). I definitely understand the “time” issue myself – and like you don’t worry too much about the speed of the process in most of my systems – but I know there are plenty of hobbyists out there who are keen to optimize as much as possible.
    Anyway – should be fun to see what happens!

    • Joanne
    • September 1, 2011

    Time saver: food processors. I throw scraps in a covered bowl in the fridge until I get a “serving size,” then chop them up in the food processor & mix with newspaper I put through my office shredder. Toss into top of bin & done.

    • yoder
    • September 1, 2011

    i think those strips will have a lot more SA than the big chunks.
    take one or two of the chunks, and the equivalent weight in strips, and do the math as to the total exposed area… i tell you, there’s a lot of UNexposed stuff in those chunks!

    • Bentley
    • September 1, 2011

    Joanne – yep, that’s a great idea! I used to juice quite a bit, and that leftover material was excellent worm bin fodder.
    Yoder – I agree 100% – I simply meant (in my afterthought) that the actual “particle size” is bigger with the ribbons. In terms of available surface area, I’m sure the chunks would offer far less

  1. I’m a firm believer of chopping as fine as possible. I have a Blentec blender that we use to make our own green smoothies and I often use it to make smoothies for the worms as well with our leftover scraps. I freeze the smoothies in ice cube trays and just feed a few cubes every day or so. These will come in very handy once the garden season is over and food scraps aren’t as readily available. The worms go nuts for this stuff. I occasionally add coffee grounds to the mix. And yes, I do put the cubes in frozen. I figure they move away from them when they’re too cold and then feast on them when they’re thawed.

    Question for you: We avoid onions and citrus by-products and my husband doesn’t think we should feed bell pepper, but I think peppers should be ok. What do you think?

    • Brian
    • September 1, 2011

    I have a Worm Inn and I find that bigger chunks work better for me. If I use material that is too blended up I tend to have problems with my bin hot composting. I think this is partly due to the great aeration properties of the Worm Inn. I’m curious how you were able avoid hot composting problems during your Worm Inn over-feeding challenge. I look forward to reading about your results!

    • Christy
    • September 2, 2011

    Particle size definitely makes a difference since the smaller the size the more surface area for the bacteria to feed on. The bacteria break down the food and the worms actually eat the bacteria.

    • Vitalie Ciubotaru
    • September 2, 2011

    A couple of thoughts.
    Well, in theory, smaller particles have greater surface-to-weight ratio, so 1lb of finely chopped carrots would have a much larger total surface than 1lb of uncut carrots. For this theory to be true, the pieces should not touch each other. In reality, 1lb of finely chopped (and frozen, and pulverized!) carrots might prove to be more bulky and sticky than a pound of uncut (or barely chopped) pieces. A pound is not that much, but if we were talking about LOTS of carrots, I could bet that the pulverized pulp is much more likely to stay anaerobic than un-frozen un-cut carrots.
    If you are really into testing the impact of particle size on worm population growth, it would make sense to have frozen, but otherwise untouched, carrots on one end and finely chopped (or smashed, or pulverized) frozen carrots mixed well with the bedding material to ensure that much of the surface stays exposed, on the other end.

    Anyway, it would be interesting to see how it goes.

    • Bentley
    • September 2, 2011

    LoL – starting to think that “How Much of a Difference Does Particle Size Make?” would have been a much better title! hehe
    My main aim is to see how much of a difference there will be between the treatments (specifically the worms in each treatment). Will the worms be bigger in the smaller particle treatment? Will they grow faster? Will the population grow faster? etc
    Colleen – absolutely NO issues with bell peppers. Hot peppers could be problematic. Cooked onions – zero issues. Raw onions – in moderation. Citrus in moderation
    Brian – thanks for sharing – that is really interesting! Definitely some situations where bigger chunks could be advantageous. If for example you wanted slow-release food/moisture (going away on holidays etc).
    As for overheating – my worm inn definitely got pretty warm during the challenge but it was cool down in the basement so that certainly helped (was during the winter) and I think in general the worm inn is pretty good for releasing heat (as compared to a plastic tub etc.
    Christy – absolutely – I’m there with you 100%!
    Vitalie – Thanks for sharing your thoughts! You’ve made a great point there – and I think it’s something people sometimes forget about. Taking blended wastes and just dumping it in a heap is probably worse than just putting a big old chunk of intact carrot etc. In this experiment, all wastes will be getting distributed throughout the shredded cardboard bedding, so this shouldn’t end up being an issue.

    • PAUL
    • September 8, 2011

    I have been experimenting with feeding my worms a slurry of steamed weeds. I gather the weeds in my back yard as I do other garden work. I steam the weeds for about 20 minutes to kill reproduction, let them cool so I don’t burn my pinkies and blend them with about 1/3 water. I dump the blended slurry into a sealed bucket with about 1/4 cup of EM, “Essential Micro-nutrients.” I let the slurry “cook,” for about 2 weeks before feeding the worms.

    My theory is: I want to find a worm food that can be found anywhere. We have weeds growing all around us. Why not use this resource??

    I am going to use lawn clippings next; then leaves in the fall.

    So far the worms have been happy chomping or doing what they do to the slurry.

    • Anthony
    • December 25, 2011

    I have a mulching lawn mower I use to break leaves and end of garden clean up. Nice break down for the worm bin 360. I pack it all in 5 gallon buckets to feed all through the winter.

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