Boulder Vermicomposting

Worm bins for offices

December 15th, 2009

I thought this exchange, on the Fort Collins worm exchange list, was enlightening, so I thought I’d post it here with comments.

Aaron Orechwa asks:

Hi I am in charge of implementing a compost program here at our office in Fort Collins, CO. Our office consists of approximately 35 people, and I thought it may be a good idea to start a composting system to divert daily organic waste into our solid waste stream. Right now I am looking into a green cone system for food waste and a rotating barrel system for yard waste as well.

Given the current climate and weather conditions, is worm composting a good idea? We will have to place the compost outside because of corporate policy difficulty in having an indoor system. Let me know if you can help or suggest any better ideas. Thanks

John Anderson answers:

Corporate policies of externalizing costs have gotten us in this environmental perdicament to start with so that needs to no longer be an acceptable practice. Worm composting can be done outdoors effectively. . What do you suppose they did with out us for 6 hundred million years? Systems can be designed to fit your resource output and our weather extremes with no on going carbon footprint. To size the system you must first need to know volume of the resource by weight on a daily, weekly, and monthly basis. Hope that helps.
See me at cowormman.com for further info. The intent of this exchange is for community households with or without composting worms to get connected and exchange their resources. Talk to you soon about possibilities?
John A. www.cowormman. com

I was unable to find sizing information on John’s website, but a bit of googling turned up this:

The rule of thumb for bin size is two square feet of surface area per person, or one square foot of surface area per pound of food wastes per week.

Making some wild assumptions about Aaron’s situation, lets assume that we can get away with 1/3 sqft/person, because each person only eats lunch at the office (1/3 of their meals), and 1/2 the time folks eat out.  Therefore 2sqft/person*1/2*1/3 = 1/3sqft/person.  (Of course, the best way to estimate size would be to measure discarded organic waste first.)  35*1/3 equals approximately 12 sqft of worm bin.   That’s only 2×6, which is probably a fine configuration.

Other considerations:

• having the worm bin outside: eminently possible here in Colorado.  Just make sure the worms can escape into the ground and insulate.  You can see pictures of John’s worm windrows here, and they definitely survive the Fort Collins winters.
• overfeeding: as Melanie Nehls Burow warns, “[b]etter to underfeed than to overfeed in general.” It’s easy to get enthusiastic and overfeed your worms, especially if you didn’t put enough in the system to start with.
• underfeeding: especially in winter, how is feeding going to happen? This is obviously a key issue, and should be resolved at the beginning
• what to do with resulting vermicompost: you’ll have a lot from a bin this size.  Give it to employees? Give it to the landscaping company? Advertise it on craigslist/freecycle?  What you definitely don’t want is to end up throwing it away.
• general maintenance: replacing bedding, removing castings and/or vermicompost, watering bin when dry.  These are all tasks that need to be done on a semi regular basis.

I think, in general, worm composting for office situations is better than traditional composting.  No work to turn it, capable of processing large amounts of food wastes (which I imagine are the typical wastes from a typical office), and relatively low cost.

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