Shoebox experiment with finished vermicompost and used coffee grounds (UCG)

[Rick]

December 18, 2012 I decided to see if used coffee grounds (UCG) could be composted just by adding some finished vermicompost.  I got a Sterilite clear shoebox and filled it 1/2 full with UCG, with paper coffee filters included, and then added a good covering of finished vermicompost.  I mixed it up a little and then waited.  December 28th I checked in on the project (plus plenty of times before that) and felt that not much was happening and decided to add some worms to speed things along.  So I added 45 mature worms to the box and then covered it with moist shredded newspaper.  I checked on it over the next few weeks but left them pretty much alone.  Today, February 21, I decided the experiment was over and wanted to see the results.  I emptied the box into a plastic bin to harvest the castings, count the worms, and see what else happened over the past 2 months.

The first thing I noticed was that it didn't smell of coffee anymore, it just had the nice earthy smell.  The second thing I noticed was that the worms were in very good shape. They were moving around alot and were nice and plump.  So I started the seperating process.  The coffee grounds were thoroughly processed!  The paper filters were gone and the coffee looked like regular vermicompost.  I ended up taking out 5 1/2 qts of compost, 60 mature or nearly mature worms, 3 tiny babies, and quite a few cocoons.

I was very happy and kind of surprised that it went as well as it did considering that the only food they had were UCG and 'finished' vermicompost.  Plus the box was so small AND it had clear sides AND no air holes drilled in the top or sides. Three things considered a no-no for raising worms. Just goes to show that when it comes to worms nothing is black and white.  

 

 

[George]

That's pretty amazing and eye opening. I would have thought you would wind up with dead worms.

I just might have to try this,

[Andrew from California]

Nice little experiment. I'm always impressed by folks with the patience to count out individual worms. I wonder how much larger the herd would've grown if you'd added a tablespoon of scraps every week or so?

[Rick]

Andrew and George, I really didn't know what to expect. All I wanted to do was see if vermicompost could be used to compost UCG. The added worms were an afterthought.
George, I should have said above that the shoebox had a lid but it didn't snap on very tight, so they did have air. But I didn't drill holes or go out of my to give them lots of airflow like it is normally suggested.
Adrew, half the box was the UCG so I think they had plenty to eat. Although I'm not sure how nutritious coffee grounds are. But I guess this little experiment did show us that UCG + 'finished' vermicompost alone are good enough for the worms to actually grow, reproduce, and I guess thrive because they were very healthy looking and very mobile.

[Metqa]

So do you think just adding some worms and bedding to a bin with coffee grounds would work as well? It seems the finished compost was not "composting" so that the worms were needed to process it in their guts.  I have access to Lots of fresh coffee grounds each week, and I'd like to recycle it as many ways as I can. Some will be mixed into my red clay soil, some has become mulch for house plants, some will become mulch for outdoor landscaping, and some is supplementing my worm bin. My bin's primary function is to process my food wastes so I don't want to overload it with coffee grounds, but if I could take out a handful of worms and have them in a separate bin dedicated to processing those extra grounds, I'd do it in a flash. I'm planning to build a couple of outdoor flow through bins for the upcoming spring, and I love new ideas.  

I'd heard that a guy fed his worms ONLY coffee grounds and they thrived, but he was only one guy. This is the second personal report I've read of worms thriving on nothing but grounds and bedding and I'm feeling more bold to try this myself.

[Rick]

Metqa,
I don't know if what I did in a small shoe box would translate to an entire bin. I think I would be concerned with a large amount of grounds heating up. Since my volume of UCG was so small and it had a week to pre-compost before any worms were added it may have settled down before the worms got there. If I were you I would set up a bin with the UCG, add some vermicompost (to seed with microorganisms), and add lots of shredded paper on top. Let it sit for a week or so, see if anything is heating up, and if it isn't than go ahead and add a handful of worms to see how they do. Good luck and let us know if you give it a try.

[Steve Lambert]

I agree with Rick's caution toward the UCG heating up if used in quantity.  So what's quantity?  I've used UCG for a lot of years and, ahem, cooked a few worms by doing it wrong.  I don't know if I've discovered all the wrong ways to compost UCG with worms, but I'm working on it.  :)

In smalll quantities (shoebox, the bag you get the coffee grounds in from Starbucks, etc.) UCG alone won't heat up.  It can though if given the right conditions.  If you dump a gallon of dry UCG right on top of a compost pile or your worm bin, it won't do much if any heating because it's dry.  If it's damp to all out wet, that same gallon would heat up; possibly to the point where worms would not like it.  I think it's the moisture of the UCG and decomposition bacteria and microbes in the compost/worm bin that interact and start the heating process; which is really from the mass reproduction of bacteria as it feeds on the UCG... decomposition.  So the bags of UCG I get from Starbucks sitting alone or in a pile with others on the ground do not heat up, but they age and grow mold.

When I feed my worm bins with UCG alone I typically layer on maybe 1/4 - 1/2 inch, either pre-moistened or I mist it until wet, and never over more than half of the bin; except if it's really cold outside and I'm wanting some heat generated from it, then I'll feed the entire top layer, yet monitor the bin temps daily so I don't bake the worms.  The thinner the layer of feed the safer you are, and you will just have to feed more often.  Actually I add a layer of bedding first, then UCG, then water misting, then put back on my top layer of dry bedding.  Most times I dust on some ground eggshell, and/or a sprinkling of composted leaves to the top of the UCG before the top dry layer goes back on.  The leaves add bacteria and microbes (like Rick's VC did) to the feed.

So, thin, damp, frequent layers of UCG can work in my experience.  However, worms seem to like some good rotted vegi waste with it better.

[Janet Kaupke]

Thanks Steve, that was just the info I was looking for. I just built a 44"x18"x18" wooden FT and I would like to use UCG, but had no idea how much was too much. I usually puree the food scraps and just add UCG from my personal use, but now I have access to a large quantity of UCG and would like to use that to supplement my feeding. I need to find alternative food sources - these guys are eating much more than I can provide with kitchen scraps!

[Andrew from California]

"...thin, damp, frequent layers of UCG can work in my experience.  However, worms seem to like some good rotted vegi waste with it better."

Yep. Old, moldy UCG can be added in larger quantities to a given mixture of food scraps. As always, much depends on the ingredients you use.

[Andrew Loy]

Nice job. I am start to use coffee grounds as the primary source of feedstock too with added vegs.. Nothing is harvest yet. Will you check the pH level of the finish vc?

[Marco Adriano]

I think your project worked because the vc has a lot of bacteria in it which broke the coffee grounds up and made it easier for the worms to eat. Vc also holds a lot of moisture and it keeps the grounds wet enough for a time long enough for the bacteria to reproduce. When you aged it, the bacteria increased. People usually forget to mix a source of bacteria with the ucg which is why they don't succeed. Great job on the project. Will try to do what you did but in a larger scale.