Hi Kayla,

Thanks for the post!

Here are some resources that may be worth looking into about Earth Tubs:

Green Mountain college own 2 Earth Tub composters: http://www.aashe.org/resources/profiles/green_mtn2007.php

A Skidmore College student has done some research into Earth Tubs for her school: http://www.aashe.org/resources/awards/2009/sarah-whateley

This forum discussion thread from last year may also be helpful: http://www.aashe.org/forums/compost-machines-or-bioreactors

My best,
Ashwini

Hi Kayla!!!

My name is Stacey Dorn, i am the head of compost at Lafayette College. In may 2010 we installed two Earth Tubs in hopes of composting all post-consumer waste on campus. We purchased two Earth Tubs and two pulping machines with a $40,000 DEP grant we received. We have been doing all of our runs with pulped food waste which is not a common thing among other universities. We have found that the pulped food has decreased the baking time needed in the Earth Tub to one week. So we load a tub for one week and then while the other tub is being loaded the other will bake. So this system has worked out very nicely for the college. Since July 2010, when I took over, we have composted over 14,000 pounds of pulped food waste. The tubs have also handled all types of food very well, we compost everything people throw away including meat and dairy.

The tubs are fairly easy to operate, I have two students complete the whole loading and turning operation each night. One person is usually not enough manpower and more than three in unnecessary. We have had some troubles with our Earth Tubs (the lids got stuck, one lid popped off, they didnt send a biofilter connection for one tub so we had to make one, etc..) but Green Mountain Tech has responded each time and sent a representative out to help.

Overall I have had good experiences with these tubs, they are great for the size of my college (around 2600 students), and if you have any more questions or would even like a visit or tour feel free to email me at dorns@lafayette.edu.

Good Luck!!

Ashwini, thanks for the great resources!

Stacey, this is helpful feedback! While we have slightly fewer students than Lafayette passing through our dining hall, I'd bet we have similar waste numbers. We were originally thinking it would take about 30 days to bake the compost, so knowing pulped food reduces that time significantly is wonderful to know! Also good to know it doesn't require many people to maintain this process.

Thanks for the information!

Kayla,
If you haven't heard from someone at Washington & Lee University on this topic, reach out to Chris Wise. W&L has one Earth Tub.

Kayla:

I have been working on on-campus food scraps composting for the past 10 years. I purchased an Earth Tub for a residential environmental education where I was one of the directors in about 2001. It failed to meet my expectation in every manner possible. The situation was so bad, that the manufacturer had to replace the tub after only a few months because the wheels on which the lid moves along the top broke through the outer plastic shell into the softer insulation. This prevented me from rotating the lid so that the auger could mix the feedstock. Unfortunately, that did not resolve the problems. The issues I encountered are: 1) the volume capacity is very small, about 1 yd3. So, unless you are generating a very small amount of food scraps on a daily basis, it will not likely meet your needs (my current program processes about 1,000 lbs. of food scraps per day). 2) the mixing auger must be moved manually. This can present a challenge for anyone who is not exceptionally strong and physically fit. At the time when I had the Earth Tub, I was a weight-lifter who could bench press well over 300 lbs. and there were times when I could barely rotate the lid to move the auger! 3) There is no way to keep the food scraps that are composting separate from those already composted. 4) the so-called biofilter is a strong attractant for bees and wasps. 5) the leachate tube caused water-soluble nutrients to be removed from the compost, thereby reducing its quality. 6) the discharge door broke off of its hinge after only a couple of uses. Based on my first-hand experiences, I strongly do not recommend the Earth Tub. The university strongly considered taking legal action against the manufacturer, but I think it ultimately decided that it wasn't worth the effort for such a relatively minor financial investment. I have also used three other rotary drum style aerobic in-vessel digesters, all of which I consider to be vastly superior to the Earth Tub.

As the Earth Tub manufacturer, we are, of course, troubled to hear of a past customer who can't speak highly of our product. Nevertheless, we consider all feedback to be an opportunity to learn and grow and do a better job. We care very much about helping organizations compost and so we always welcome opportunities to improve.

With more than 150 Earth Tub installations nationwide and more than 15 years of proven experience in the field, the Earth Tub is the most popular composting system of its size in the United States. And there are many, many, happy, successful installations of Earth Tubs around the country.

The Earth Tub is a tool for optimizing hot, aerobic composting while preventing offensive odors and pests. We know that the Earth Tub does an excellent job at this task. And, if a customer encounters any difficulties, we are eager to work with them so that they can focus on making great compost.

That said, we want to offer a few clarifications:

1. Capacity. The author criticizes the capacity of the Earth Tub. First, to correct the facts, the actual total capacity of the Earth Tub is 3 cubic yards not 1 cubic yard. The Earth Tub is designed to process up to about 150 lbs of biodegradables per day. This is not a product defect and is instead simply the designed capacity of the Earth Tub. If larger processing capacities are desired, we offer an excellent larger and more automated composting system, the Earth Flow, that can process up to 1.5 tons per day,

2. Manual Rotation of the Lid. It is true that the lid of the Earth Tub is rotated in order to move the mixing auger throughout the compost. However, the rotation of the lid should not require extreme force. Often, we find that that the Earth Tub is not installed in a level manner. This can cause the Earth Tub to become slightly out of round which can make the lid difficult to turn. This problem is easily resolved by leveling the base of the Earth Tub to remove any eccentric strain on the tub. Again, we are happy to work with our customers to make sure our systems perform as advertised.

3. Batch vs. Continuous System. The author expresses irritation that there is no way to keep new food scraps separate from previously composted material. We understand this concern. However, this is not a product defect but is simply a characteristic of a batch composting system (incidentally, drum technology often also functions as a batch composting system). If a batch composting system is being fed continuously, it is typically necessary to have two systems, one that is being fed and one that is "cooking". However, many of our customers are able to use single Earth Tubs by scheduling the unloading of their Earth Tub during school breaks. The author is correct, however, in pointing out that there are advantages with a continuous composting system. Our larger Earth Flow composting system is a continuous composting system that offers these advantages and more.

4. Biofilter Attracts Bees. We have never heard of this concern before and it is not clear how this would be an issue, given that the biofilter is housed in a closed container. We recommend that our biofilters be filled with a course wood chip such as a pine bark nugget. We wouldn't expect that this would attract bees or wasps. However, it is important to periodically spray the wood chips with water to keep the filter media moist. This maintains the effectiveness of the biofilter (at filtering air) and would have the important side effect of discouraging bees and wasps from taking up residence. Again, this is not a product defect and would apply to any biofilter technology.

5. Leachate. The author expresses concerns about leachate removing water-soluble nutrients. We understand this concern but again feel that this should not reflect poorly on our product. The Earth Tub does have a leachate drain for collecting excess liquids. This leachate can be collected into a container and then recycled back into the compost. Thus, there is no reason for those nutrients to be lost. Furthermore, proper management of the compost (e.g., using bulking material) can reduce leachate to a minimal level. Once again, this is also not a product defect in any way.

6. Discharge Door. The author reports that their discharge door broke after only a couple of uses. This is not something that we have been aware of as an issue. If this were the case, this would be a warranty issue and we would be responsible for providing a replacement.

We are very proud of our systems and we believe that they provide unique advantages to universities and colleges in helping them create excellent on-site composting programs.

We are happy to answer any questions about the Earth Tub, the Earth Flow or any of our other composting systems.

Van Calvez
Sales Manager
Green Mountain Technologies
van@compostingtechnology.com
(206) 319-7102
www,compostingtechnology.com