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Reviews – Mid- and Large-scale Continuous Flow Systems (cont.) E-mail
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Written by Administrator   
Sunday, 11 September 2005
Oregon Soil Corporation Reactor (OSCR)

Specifications:

Length: 4' (photo: built 8' long)
Width & Height: 3'
Surface area: ~12 ft2

OSCR Plans Features:

  • 56-page construction & operating guide
  • All wood construction
  • Easy-access harvest chamber
  • Optional insulated/heated compost chamber



OSCR Review,
by Pat Reed

I just finished building the OSCR worm bin last week and I love it. It took the better part of three weekends to complete it. Maybe if I were better at woodworking it might have gone faster.

Through the course of cutting and assembly I could tell that much thought went into the design. I followed the directions carefully and applied the primer coat of paint before assembling all the pieces. There were a few things that didn't measure out perfectly, and because of this, I would recommend 'ripping' at least one extra 2 x 4 (but not cutting it into pieces until needed) Also, my skill saw expertise left something to be desired as the bin was slightly out of square when finished, so it might be wise to get the plywood cut at the lumber yard.

If I could offer the authors of this plan one suggestion, it would be to have a couple of photos of a finished bin as well as one partially finished. The line drawings are great, but I never knew what it would look like until I had it built. I didn't know the heater (btw, very cleverly designed) would slide out of the box when unneeded, or how the bottom of the bin could be harvested...so I shot some photos during construction to share with anyone who wants to see them. (If that's permissable with the authors)

I used stainless steel cable for the bottom which I obtained from a person who builds salt water fishing gear.

The soil heating cable I was lucky enough to find at a local nursery which had had it on the shelf for three years...the only one left.

I beefed up the bottom of the bin with 2x4's screwed and glued to the bottoms of the plywood so I could get a hand truck under it to move it. It's heavy.

Instead of cement or 6 mil plastic on the harvesting floor, I cut a piece of 1/8 inch masonite to fit, so when the castings come down, I can pull the masonite out like a drawer, and scoop them up with a dust pan.

I had considered building the OSCR many months before I actually bought the plans. I wondered if it was worth the cost and if I could accomplish the job with my limited knowledge of carpentry. I also wondered if I really needed a bin that large (12 square feet sounded huge)

During the summer months my little herd grew bigger and I realized that my plastic bins were not rodent proof. I might have problems during the winter. There was also the fact that the sideways migration plan I was experimenting with was probably not as efficient as the upwards migration that OSCR uses. After the three coats of paint were applied, and all the fittings, I was finally able to dump the worms into their new lodgings. This took some time as I was trying to harvest the castings at the same time. My slogan was "No worm shall be left behind."

In conclusion, the plans contain much more information about how to start the system, what to do if there are any problems, and how to incorporate vermiculture into a school situation. They are worth the cost, because I now have a bin that is rodent proof, heatable, and continuous flow.


OSCR Review,
by Philip Jones

I bought the plans and site license for an OSCR bin last summer and finally got around to building it about six weeks ago. I found it pretty straightforward to cut out the pieces and get the OSCR built following the instructions, but I have a shop full of woodworking equipment. All told, I spent about six hours getting it built and about four days getting it caulked and painted.

The OSCR is built from two and a half 4' x 8' sheets of 5/8" thick exterior plywood and five 8' long 2x4s. The plywood has to be cut into seven pieces (two for the front and one each for the top, bottom, back, and two sides). Unless you have a panel saw designed for cutting sheet goods, I recommend that you have the plywood cut into pieces for you at the lumberyard. Most lumberyards will do this for a small fee, and you will save yourself a lot of time, trouble, and potential danger by having the lumberyard do this. The 2x4s need to be "ripped" (cut lengthwise) in half before cutting the resulting pieces into a variety of shorter pieces for interior framing and structural support. I do not recommend using 2x2s to avoid the ripping operation: the 2x2s will measure 1.5" x 1.5" while the ripped 2x4s will measure 1 1/2" by 1 11/16". Sacrificing that extra 3/16 inch by using 2x2s will cut back on the unit's strength. Again, if you don't have a table saw, get the lumberyard to rip the 2x4s for you.

I found the measurements given in the plans to be accurate (this is more unusual than you might think), and I strongly recommend following the assembly sequence given to you in the plans. The authors have carefully thought through the assembly sequence, and I guarantee that deviating from their instructions will turn an easily do-able process into a more difficult one. During assembly, the structural support pieces cut from the 2x4s are glued and screwed to the plywood pieces. I recommend using a water resistant glue (like Titebond II) and galvanized screws. Since you'll be driving a lot of screws, a cordless drill with a clutch will save you a lot of time. Additionally, a couple of clamps will help you hold the pieces in their proper alignment while you are drilling, countersinking, and driving the screws.

The authors provide an estimate of $153.70 for the total cost of the basic OSCR. I found this to be about on target. Although I paid more for some items than the authors estimate, I also paid less for others, so things balanced out. Two items that I had a little trouble finding were: 1) a 70 foot length of weed-eater cord, and 2) a 5# box of Rocktite brand pourable cement. The weed-eater cord is used to form the "bottom" of the composting chamber by weaving it back and fourth from the front to the back of the OSCR through holes you drill. The pourable cement is poured around the drain in the harvest chamber floor to form a surface that directs water run-off to the drain. My source for the weed-eater cord was Country Home Products (800-446-8746). They sell very thick (130 mil and 155 mil) cords in 150 foot rolls. The Rocktite cement is like no other product I have ever seen, and I strongly recommend you not try to substitute. Rocktite is made by Hartline Products Co., Inc. (216-291-2303).

The most difficult part of the whole project is getting it painted. You have to paint it inside and out with 3 coats of paint (1 coat of primer and 2 coats of exterior latex). Since there's no way to paint all surfaces at once, you are constantly doing a partial paint job, letting it dry, turning the bin, painting some more, etc.

I've got the OSCR set up in the basement now with 12 pounds of worms and they seem to be doing fine. One word of caution. The OSCR is 3' wide, 4' long, and 3' tall. My 3' door to the outside was actually only 35" wide. That's why the OSCR is in the basement.



Earthworms Make Great Waste Managers,
A Large-scale Continuous Flow System


An Australian company, feeds this type of reactor to convert of over 20,000 metric tons of mixed organic wastes per year into vermicompost.

Vermitech Systems

Specifications:

Width: 7'
Lengths: Modular 8' worm bed sections, 2' for equipment, thus, 10', 18', 26', etc.

System Features Include:



Vermitech 200 review,

by S. Zorba Frankel

The Medical University of South Carolina also uses a Vermitech system to process roughly 200 pounds of cafeteria food waste each day. Since July 13, 1999, the recycling team has been picking up a 32-gallon plastic tub from the University's main cafeteria and taking it to the worms' lair.

The University uses a larger Vermitech system, 18' long by 7' wide, to handle their organic waste. Unlike the Grand Traverse system, this bin has no lid. Instead, several bars curve upward and span the width of the bin. When temperatures are cool, these bars support a thick tarp that covers the bin. The composting chamber consists of two eight-foot sections and an air conditioner and hydraulic equipment occupy the last two-foot section. They also use a Vermitech shredder with an attached conveyor belt that delivers the feedstock to the bin.

Christine von Kolnitz, MUSC recycling coordinator, led the process to bring worms to the University. She likes the Vermitech system very much. “They eat it up as fast as we shred it. We can't feed them enough. Also, it's not too labor intensive.” They shred up the food and the conveyor sends a large pile of food and cardboard onto the surface of the bedding. They use a rake to spread out the food and then they clean up. Once a month or every two weeks they turn on the hydraulic system to cut off the bottom layer of castings. Once the castings are scooped up and put in a cart they clean the floor and they're done. The grounds department says they can use all the castings the worms can provide. The system for MUSC has a payback of three years. Christine has only one dislike for the system, that the shredder leaves some material in the drum, which they have to sweep out.

For their new system, MUSC constructed a small structure, beginning with an 18' x 24' sloped concrete pad with a drain. The pad is coated with acrylic so that castings can be cleaned up easily. The structure also provides electricity, water and airflow. A large fan that forces air out high on one side of the building, and draws air in next to the bin, creating a flow underneath and through the bin. Funds for their project came from several sources, and their startup costs, including the building and supplies, were $54,000.

They learned a lot through their hands-on experience. Initially they used newspaper as a carbon-rich portion of their feedstock, alternating between shredding newspaper and food waste, then raking out the pile deposited in the bin. This worked, but sometimes left some larger, dry chunks of newspaper. They then tried feeding just shredded food waste. That was better, but the excess moisture created caused worms to go "on tour," crawling down and onto the floor. They've found that cardboard works better for them and mixes better than food. At this point, they find they only need to add minimal water to the system. Altogether, they spend an hour and a half working with the bin each afternoon.

Because this is Charleston, SC, the air conditioner unit, which is built into the unit, stays on all the time in summer. During the winter, the outside vent is covered and the tarp remains on the bin except during feeding.

Vermitech 100 Review
by Randy Smith

Here in Grand Traverse County, worms are processing 5-35 pounds of food scraps each day in their home, a Vermitech 100 system. Since setting it up on Earth Day, 1998 in our County Building, it has accepted all the preconsumer and some of the postconsumer food waste from our building's cafeteria and some of the food waste from our Sherriff's 159-bed jail. The system has a 4' x 8' enclosed bed with insulated panels and stands 3' tall, with two panels on top that hinge open. A large shredder, also designed by Vermitech, blends paper and food waste into a homogeneous blend and shoots it into the top of the bin through a spout. The worms - all 100,000 of them, we estimate, are in an 18" bed laying on a grate. This is a continuous flow system, with a bar that is pulled across the top of the grate, "slicing" off an inch or so of vermicompost with each pass. We add material until it's within a couple of inches of the top of the bin (thus giving it the maximum amount of time in the unit) and shave off 3"-4" of vermicompost at a time, about once a month. Doors open below the grate to allow access to the finished materials.

It's a good system. However, it's not just like operating fifty small worm bins. Like any living system, it works best the more regular you are with feeding and maintenance. Since our food source depends on what people don't eat, it's highly variable. The waste paper we feed comes from our restroom hand towels and napkins from our cafeteria. The paper carbon source is fairly consistent, but the nitrogen food waste varies a lot in moisture and volume and is seasonal. In the summer we have a lot more fruits and vegetables than in the winter, not as much. So we've had to adjust our operation to work with that fluctuation in feedstock, as well as complement our labor.

The County custodians manage the system, located in the basement right next to the cafeteria. Our health department required that it be vented to the outside, which we accomplished through the building's existing exhaust system. Six custodians are involved with our soil factory. Two custodians take charge of grinding and feeding the system. The others collect the materials for the system. They do a very good job, and the system would not work without their participation.

When we began to consider the location for the system, we decided that an area used to store extra furniture and office equipment looked best. We had to redesign and upgrade the room. We tiled the floor, added a wall, a door, ventilation, insulation and electrical 3-phase power. Essentially, we created a smaller room within a larger room. We wanted to be sure that the blending operation, which makes a certain amount of noise, wouldn't distract or interfere with other workers. As it turned out, the night crew would do the blending at 11pm, eliminating the concern altogether!

Ours was the second Vermitech system manufactured. We budgeted $15,000 for the project. We also received a $1,650 grant from our local community foundation, and we came in under budget. I believe it is a great value. If we maximized the use of the system, we could save $5,000 a year in disposal costs, get a valuable soil resource and help the environment. We aren't receiving as much food as expected from the jail, so we currently figure that the payback period will be five years.

We've learned that watching conditions in the bin carefully pays off. For example, in summer, when we get a lot of melon, we often see temperature increases and so we'll throw a little ice in the bin, fork the bed and open dampers to allow more air movement. Another difficulty we've learned to work with is keeping adequate moisture in the bin over the weekend or extended holiday. When we initially considered the system that exhausts air from the bin, we thought, "that's great; oxygen will be drawn into the bin from below." What we didn't realize is that it would dry the system out as quickly as it does. So, to prevent drying, we add 1-2 gallons of water per day.

On the other hand, Vermitech told us to aerate the 4' x 8' bed material with a garden fork -- to stick the fork in and wiggle it around a bit. But, with our exhaust system and the custodians' attention to detail, we don't need to do that, saving up to 30 minutes of work daily. We check for clumps of dried material, and we find these every so often, when we forget to water it regularly, like after a three-day holiday weekend. Arrangements need to be made to get more water in the bin. Otherwise, we'll be six gallons shy by Monday. We have tried using wet burlap over the top, putting plastic over the top and damping off the ventilation for the weekend. But what actually worked best is something one of the operators tried -- layering ice cubes on top of the decomposing food. It melted slowly and did the trick. I can't give enough credit to our custodians that operate the system: they do an excellent job. Oh, one more tip: when we give a lot of tours, the open lids drys the bedding, so we add more water.

During the planning stages in 1997, we had a lot of interest in the worms! Practically everyone fishes here. There is a lot of interest in selling the worms and using the castings, particularly by the grounds department. But, we see about a 90% volume reduction by weight in the material we put in. So this "Soil Factory," as everybody calls it (nobody knows what a "Vermitech" is!) puts out a minuscule amount of vermicompost compared to what went in! And so there's some disappointed folks around here!

The bin equipment has been real sturdy. The shredder has had a couple of upgrades. A safety breaker in the blender would trip repeatedly, and they replaced it with a heavier-duty model. The blades also have been upgraded, and Vermitech modified them for us under their warranty. So their service has been very good.



Holcombe's Earthworm Reactor

Editor's Review
by Kelly Slocum

In 1991 Dan Holcombe, president of Oregon Soil Corporation, built a vermiprocessing table based on the continuous flow design developed by Dr. Clive Edwards in the 1980’s. Referring to it as a “worm reactor,” the system was designed so that it could process large volumes of organic material and produce large volumes of vermicompost under the management of a single operator.

Holcombe’s worm reactor is a modular unit approximately 40 inches high over all and eight feet wide, with a working bed depth of approximately 24 inches. Because of it’s modular design it can be built to almost any length, with the unit Holcombe currently operates being 125 feet long. This gives the unit 1000 square feet of surface area.

The floor of the working bed is made from hog wire to enable the finished vermicompost to fall through when harvested. Finished vermicompost tends to hold together, even when resting on the wide hog wire floor, and does not readily fall through the mesh openings. The material needs to be disturbed to enable harvesting. A floor made from a small mesh size would effectively hold the vermicompost in the unit, making harvesting far more difficult, if not impossible. Holcombe initially sets up the reactor by laying several sheets of newspaper over the hog wire and bedding on top of it to prevent the fresh material from falling through.

To enable one person to efficiently feed the system the reactor uses an automated overhead gantry to deliver a consistently even layer of feed stock to the bedding surface. Feed stock is shoveled into the gantry which runs along rails set on top of the bin side walls, spreading a thin, even layer of feed stock. At peak operation Holcombe’s worm reactor can process roughly 6000 pounds of organic material per day, feeding approximately 6000-7000 pounds of worms. Feed stock consists of produce waste picked up from several Fred Meyer grocery stores in the Portland Oregon area. Dan spent several weeks working with store employees, teaching them to remove plastic wrap and rubber bands so the feed stock would not be contaminated with materials that would not break down. The produce waste is picked up from the grocery stores, mixed with compost to aid in absorbing excess moisture and ensure good porosity, and fed to the system the same day.

Holcombe’s worm reactor is housed in an unheated greenhouse to protect it from the nearly constant winter rains in the Pacific Northwest. System temperature is maintained by the microbial activity in the decomposing feed stock. Keeping large scale systems cool enough for worm activity is more of a challenge than keeping them warm, requiring that Holcombe monitor the system’s feeding rate carefully to ensure overheating does not occur. Moisture is monitored closely and Dan uses a hose to add water if necessary. Because produce waste is high in moisture varying volumes of compost are added to each load of feed stock to balance the moisture level for optimum worm activity.

The worm reactor uses an automated harvesting system to remove finished vermicompost from beneath the table. A breaker bar dragged across the hog wire floor shakes loose a thin layer of vermicompost which falls through the wide mesh. A series of automated paddles are then engaged to scrape the vermicompost from under the table so the operator can shovel it into a pile for drying. At peak operation Holcombe’s system produces approximately two to three tons ( five to seven yards) of vermicompost per day.

Last Updated ( Sunday, 02 October 2005 )
 
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