Wednesday, August 17, 2011

A new vermicomposting bin

Well progress can really be slow, but I think that as long as you can keep up on the day to day stuff and occasionally make some progress on the extra stuff, you will eventually get somewhere. I wanted to document my progress with my vermicomposting project. The garden has done reasonably well in a few aspects but it is still abysmal in others. (Half the corn didn't even come up, and what did is less than a foot high.)

Red Wigglers

Back in June, I found that a local farmers market had a organic farmer selling garden seedlings and red wiggler composting worms. Since my budget has dictated that I start out small, I decided against ordering a large amount of worms from an online vendor. There are a lot of different ideas for worm bins with different pros and cons, I think it is actually better to start with enough worms to see some real progress but not so many that you can't deal with them all. I chose to purchase one pound, which is approximately 1000 red wiggler worms, and costed about $30. With the shredded cardboard bedding, the worms came in two large yogurt containers.

Unique worm bin based on experienced vermicomposters

My primary inspiration for the bin came from multiple plans for bins at I didn't want to spend a lot of time and money building a wooden bin without understanding what the worms would need over time in my local climate, not to mention that a large wood bin would be very heavy. I decided to choose a plastic bin with handles and a lid that could be easily removed.

My other inspiration came from the commercial vermicomposting bins that are somewhat shallow and can stack up to six bins high. They have small holes at the bottom of each bin so that the worms can migrate upwards and the excess water can drain downwards. They have small vents in the sides for increased air circulation. Even though many bins will stack, it would be important that the bins would have some space between them even when stacked so that the material in the bin would not be compressed, crushing the contents of the lower bins. I would also be important to add enough compostable material that the upper bins would touch the top of the vermicompost in the bin directly below it, otherwise the worms would not be able to migrate upwards.

I decided to purchase two long, shallow, plastic bins at initially, the type that slides under beds for storing sweaters and other seasonal clothing. I would have preferred one that wasn't quite so long, but all of the other bins that I found to be this shallow were much too small, the size of a shoebox. I would have also preferred bins that were not clear because worms will avoid the light. (I found a dark shelf in my garage, so hopefully this won't be an issue. I added strips of cardboard around the sides to also help with the light problem.) The bottom bin I left as-is to allow it to collect any water that would drain out of the upper bins. It would also catch any worms that decided to escape from the upper one. The upper bin I started using a awl to poke holes through the plastic but I found that a drill with small bit was more effective. I drilled dozens of holes in the bottom, a single row of holes in the sides towards the top, and a number of holes in the lid for ventilation. 

For worm bedding I used a layer of well composted material from my outdoor compost bin (about four months old), shredded newspaper that I sent through a paper shredder, and finally some slightly composted kitchen waste that was starting to break down in a different compost bin (about a week or two). I made sure that each layer was moist before adding the worms to it. I finally added some damp cardboard that I tore with my hands. Over the next few weeks I found that the thicker cardboard was better than the newspaper for retaining moisture and acting as a mulch for everything below it. The worms wouldn't come all the way to the top unless it was damp. I also found that after a few days there was a lot of water that had condensed in the top bin. I initially left off the lid just a crack to eliminate the moisture but then I drilled in quite a few more holes in the lid to allow for better air flow. Every other week I would take soft vegetable or fruit trimmings and bury them in the worm bedding. I also added a sprinkling of water around the edges that tended to dry out quicker.

Initial Results

By the end of July, the compost, newspaper, and cardboard had all been nearly broken down, with a large amount of worm castings and new worms mixed throughout. The two small containers of worms had spread throughout the bin with a large amount of cocoons and juvenile worms as well. I'm curious the exact propagation amount, but I'm not prepared to sift through the entire bin to count. I knew that I would need to start another bin soon as a new home for the expanding worms.

By mid August, I purchased a third plastic bin that would fit inside the others. I prepared it like I did the second bin with the exception of the lid. Since the bins would fit inside each other, I didn't need to use the lid for the new bin at all. Instead I can just use the old lid that is already full of holes for air flow.

Next Experiment

Purposefully, I didn't put any of the red wigglers into the new top bin by hand. I'm hoping that my plan works and the worms will migrate through the holes into the upper bin. Of course there are a number of things that could go wrong: drilled holes too small, upper bin environment not acceptable, air gaps between top of compost and bottom of bin doesn't allow worms to reach holes in upper bin, and I'm sure that there could be others. If all goes well, I can check in a few weeks to find worms in the upper bin. I'm going to leave it there for about a month before I try to remove the worm castings from the lower one because I would rather that the cocoons would hatch and the juvenile worms would be able to migrate upwards, instead of being mixed in with the outdoor soil and lost as a resource for my vermicomposting experiments. I'm sure that I won't get them all, but I'm hoping that this approach will be more successful than the other techniques that I have read about by sorting through the bin by hand.