Lafayette College recently installed two 'Earth Tubs', which use external energy only to stir the mix [or you can do most of it by hand].  These are very efficient units, and they expect to be able to compost all their campus food waste. I'll see if I can get someone from Lafayette to respond to your post.

Some other schools have installed added-heat composting machines. The added energy speeds up the process to less than 24 hours -- but it's a step in the wrong direction for carbon-neutrality [unless they power it entirely with solar PV].

I believe Allegeny was the first in PA to install an in-vessel compost system back in 2001 with help from a grant from the PA-DEP (which are unfortunaltely no longer available). See http://www.wrightenvironmental.com/html/pennsylvania.html

Unfortunately, we don't have a farm like Dickinson, or a local processing plant like Swarthmore, so we would also need to purchase an in-vessle system if we wanted to process all our organic waste on site.  There are a number of different models on the market now; no matter which method you choose though it will require some energy imput.  Even the Earth Tubs at Lafayette use about 1088 KWH per year.  http://www.compostingtechnology.com/invesselsystems/earthtub/

One system that we have investigated recently is very popular in the UK now; its called the 'Rocket' and is a continuous system that is loaded daily and starts producing compost in about 2-3 weeks.  It is uses about the same amount of electricity as the Earth Tub but is a lot less labor intensive to manage.  http://www.natradinghouse.com/rocket.htm

Would love to hear if there are other campuses who have purchased in-vessel compost systems, or have researched/implemented other options for on-campus composting!

Sara Tower `12

Gettysburg College

 Michelle:

I applaud your efforts.  I have been working for years to instigate a movement to encourage colleges and universities to lead the way in such a sustainability initiative.

I have been operating an aerobic in-vessel digester for the past 3+ years.  For 2+ years I operated a system at Montclair State University that processed about 500 lbs/day of food scraps.  The processing time was 5-7 days for a stable compost.  For the past 1+ years, I have been operating a system I custom designed for Kean University.  It is capable of processing 1,000 lbs/day of food scraps.  The processing time is the same.  I have also used an Earth Tub; however, my experience was completely negative.  Contrary to Peter's experience, I did not find it efficient and the turning of the auger to mix the feedstock is extremely difficult.

If you would like to read more about my project, please visit <http://www.kean.edu/~sels/resources/greenmachinearticle.pdf>.   You may also contact me directly at 908-737-3613 or nsmithse@kean.edu.

Nick

I work for a large urban university, and we are breaking ground next month on a dry anaerobic fermentation plant that will generate electricity and heat.  The size of the plant has more to do with energy (up to 10% of campus electricity and heat) than organic waste (the campus food and yard waste is only about 5% of the feedstock needed).  I realize this may sound like overkill for this discussion, but it is an interesting model for urban settings, and small-scale options may be possible (we toured a small BioFerm plant at the Munich Zoo in Germany that would probably fit an average US college).  The facility is a closed building with biofiltration of air to control odors.  We have a 2-acre site, zoned light industrial, next to a large campus building  (Facilities Management).  Other heat customers in the neighborhood include a technical college and a senior center.  It is across the street from a municipal sewage treatment plant (will we even be noticed in terms of odors?) that is donating their excess biogas production (which they currently flare off to reduce greenhouse gas emissions) if we build a pipeline to our generators.  It is also across the street from the city yard waste drop off site, which will contribute about 15% of the feedstock for the plant.  Over the 20-year life of the plant, we hope to help Oshkosh become one of the first US cities outside California to initiate curbside organic waste collection.   The last points are that the plant does not produce wastewater, but it does result in large amounts of partially-composted solids.  So we still need arrangements with outdoor composters (outside the city) who can finish it off aerobically, but we are trying to arrange 2-way truck shipments where we pickup feedstock and drop off the partially-composted material.

Since we are in the midst of settling contracts, I'll refrain from giving any financial details, but please contact me if you would like more information.

Thank you so much all of you for providing me with information and food for thought.

Nick, congratulations on building such a great digester...I can see your dedication and passion.

Michael, what a perfect storm for your facility with all of the different inputs and partners.  I wish you all the luck with the contract settling.

The campus I am currently at is built out to the max and a facility of really any considerable size in not exactly an option.  I collected data about various composting machines and gave it to the ones that make the decisions.  From what I understand they are leaning more towards a in-kitchen composter that will only handle pre and post consumer food waste. 

Best,

Michelle

Hi Michelle,

To piggy back on Peter's comments about the Earth Tub, they are great little units. My word of caution is that with any batch style composter, you really need 2 units. There is no segregation in the unit to prevent new material from blending with partially composted materials.

There are continuous throughput machines like the Wright Environmental systems that do a great job of segregating new from partially finished materials. However, they do use a fair amount of energy to move material so that may not be as compatible with your overall sustainability goals (though I would really encourage a lifecycle analysis that compares the emissions of the direct power use vs the methane emissions reduction of getting stuff out of the landfill in the first place - and the soil carbon absorption benefits of using the compost in soils).

Another viable option that would give you the segregation benefits without the higher power use is a rotating drum composter. We did some very favorable tests of the BW Organics drum composters at a school I was working with. Has a simple belt driven drive that uses fairly little power in comparison to other continual throughput units.

Hope this helps.

Is anyone familiar with the "IPS" compost agitator? I am looking for some aftermarket parts and am experiencing a great deal of difficulty. direct purchasing from the company has been the only route I have found, but it is terribly expensive. Any leads would be greatly appreciated.
Carlton