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Micro-Bins Compost FAQ

Aerated Micro-Bin System - Frequently Asked Questions

1. Why do the bins come apart?

The bins do not have to come apart. We thought that if the bin could be disassembled, you could set it up in the area you plan to use the finished compost to minimize handling. Also, after 30 days of active composting, you could remove the bin and reassemble it to begin another batch, while allowing the first composted pile to sit and cure for an additional 30 days. Removing the bin will also allow you to easily pick up and transport the compost with a tractor. Back to top

2. After the 30 days of curing is complete, can the bin be reused to start another batch?

Here is my thinking on how to best operate the system. Once you have completed the active phase of composting, the four sides of the bin are disassembled, moved to a new flat location, and reassembled. It can then be filled either daily (i.e. progressively) with fresh manure, or immediately with stockpiled manure (although it shouldn't be much over 30 to 60 days old). The manifold can be moved and if you want to go to the trouble of recovering the pipes beneath the original pile, these too can be reused. Alternatively, you can simply use new sections of aeration pipe to connect up with the original manifold. Back to top

3. Do you recommend installing more than one bin?

The ideal setup would be a three-bin system. One bin would be filling while the second is composting and the third is curing. Three bins would allow for continual rotation with the air flow being diverted from one bin to the next as needed. Back to top

4. Should the bin(s) be constructed on a cement slab?

The idea of the micro-bins it to keep aerated composting as simple as possible. Concrete will help but it is not critical to the composting process. With regard to water quality, we always want to prevent compost leachate from entering standing or flowing bodies of water. I think that level ground is a more important factor than soil vs. concrete. If you bin is placed on level ground, the forces induced by the compost on the side walls of the bin will be less likely to cause it to slump to one side. Back to top

5. Why is only the front panel braced?

The front panel has a horizontal brace so that the upper section can be cut and temporarily removed to make it easier to lift the manure into the bin. It is only replaced as the manure reaches the top. Back to top

6. What is the purpose of the valve?

When the valve is placed between the blower and bin, it allows you to control the volume of air going into the bin which allows further control of the pile temperature. When one blower is used to provide air to two bins, it allows you to adjust the proportion of air going to the "old bin" and "new bin", which requires additional oxygen at the early stages of composting. Back to top

7. Is it better to buy the optional manifold from you or can I purchase the materials locally?

All of the parts for the aeration manifold should be readily available at your local hardware store. The training manual specifies which parts to purchase and the related lengths of pipe to cut. We offer the manifold kit as a convenience for those prefer not to go to the effort to obtain, cut, and assemble the materials. Back to top

8. Is glue recommended on the couplings and pipes for the interior of the bin?

Glue is not necesssary. I would recommend using duct tape if you have problems with pipe separation. Back to top

9. Should the holes in the manifold pipe face up or down?

We recommend that the holes in the pipe be placed in the downward position. Typically, the manure will get enough air in the Micro-Bin even with the holes facing down. That said, if you feel it is necessary, it certainly won't hurt to add a couple holes to the side of the pipe as well. The rate of air flow is best controlled by the optional gate valve and not by the number of holes or their location. Back to top

10. If I drill my own holes in the aeration pipe, what should their size and spacing be?

If building a second or third bin, you can save time by purchasing perforated pipe with the holes already drilled. However, if you wish to drill the holes yourself, we would recommend that they be 3/8" and spaced approximately 4" apart. Back to top

11. How long can unprotected plywood be expected to last?

Marine grade or treated plywood will certainly last much longer than untreated. Unfortunately, I do not yet have a good idea of how long the wood can be expected to last. Unless the plywood delaminates because of exposure to wet conditions, I would guess that it will last at least a year. Back to top

12. We rarely experience freezing temperatures. Is the insulated bin necessary?

If you seldom experience freezing temperatures, the insulated bin will likely not be necessary. However, our objective with composting is to achieve temperatures of 131oF for a minimum of three days. During periods of prolonged cold weather, this may be difficult to achieve in which case insulated wall panels may be warranted. Back to top

13. Do we need to provide the blower with a weather-proof cover to protect it?

While the blower is designed for all weather conditions, I would expect it to last much longer if covered up. What works well for me is an inexpensive Rubbermaid tub with a "mouse-hole" notch cut out of one end and placed (inverted) over the blower and extension cord plug. You don't want a tight fit because we need a way for air to flow easily in through the notch. I put the blower up on a couple of bricks so that it's not directly on the ground and then place another brick on the cover to keep it from blowing off in a storm. Back to top

14. Does the manure pile need watering on a routine basis after the blower is started?

The right moisture content is critical and during the summer months, desiccation is a problem. to prevent overdrying, one option would be to construct a simple 8' x 8' frame made out of 2" x 2"s with corner bracing. Use a staple gun to attach a layer of plastic sheeting (visqueen) to the frame. The frame could lay flat on the fresh, wet surface. To add new manure, prop up the frame (front side up). After the new manure has been added: rake flat, wet down, and lower the frame back in place. Back to top

15. What if we get a lot of snow or rain - will it affect the system?

Yes. Too much rain or snow can affect the pile temperature which, in turn, impedes the effectiveness of the aeration. If you anticipate either of these conditions, we recommend placing a tarp over the top of the bin while it is filling. Once the bin is completely full and you're ready to turn the air on, put a 6" layer of sawdust or bedding on the top before replacing the tarp. Back to top

16. Do I wait until the bin is full before turning the air on?

Yes - and keep in mind that the "30 days" of composting is a flexible time frame. The goal is to reach a temperature of 131 degrees for at least three (3) days after the bin is full and the blower is turned on. It is possible to reach that goal in less than 30 days. Once the temperature begins to fall, the aerated composting process is essentially complete. If you need to re-use the bin, the compost can be removed at that point and placed in an area to "cure" for another 30-60 days. Back to top

17. Under what conditions should I restrict the volume of air flow when using a gate valve?

Most people find that controlling the volume of air by the frequency and duration of air flow is adequate, with the exception of extreme cold weather conditions. However, the valve may be used to further congtrol the volume of air going into a single bin. In this situation, I would suggest beginning with a 1/4 open valve setting combined with a 30 second on-time every 30 minutes. As the pile temperature comes up, progressively increase the openness of the valve within the first 3-4 days of operation and observe the change in temperature within the pile. Note: to determine temperatures at different depths in the pile, you can drill 3/8" holes in one side of the bin and insert your temperature probe horizontally. Alternatively, the valve gates are also used to balance air flow between two separate bins. Back to top

18. How do I know when the curing is complete and that bin is available for its next load?

You can most easily tell when compost is well cured by the way it looks and smells. It should have a dark, uniform texture and it should have a gentle, soil-like fragrance. A sharp or sour odor indicates that it is not done. In an ideal world, earth worms will find it and further enhance the quality. Back to top

19. What if I decide to convert from the small, portable system to a larger, permanent system?

All Beta-Test Participants are eligible for a $500 discount on an O2Compost Bin or Bay Training Program. In some cases, participants may discover that a small portable compost system does not meet their operating requirements and that a larger, permanent system becomes a “must-have” item. In this case, we are ready to rebate the cost for your Beta-Test program in exchange for the original Starter Kit blower, timer and temperature probe. Back to top

20. Is my observation correct in that the hexagon model appears to hold three times more?

Yes. The hexagon-shaped model does have a larger capacity. While it will take longer to fill, the greater volume will help you retain heat, thereby expediting the composting process. Back to top

21. I'm using wood pellet bedding. Should I use this for the recommended 6" layer over the pipes?

Since you are using wood pellet bedding, there will be sufficient porosity in the mix itself and, therefore, no "6-inch layer" will be needed. This applies when the mix of materials is dense and restricts airflow. You never want to use hay or straw to cover the pipes because when it gets wet it loses its structure, becomes "slimy" and actually restricts airflow. Back to top

22. Can I use wooden pallets for the side of the bins?

You can certainly use pallets to serve as your side walls, however this does compromise the airflow by providing pathways for the air to short circuit. Similarly, with a clean gravel base, air may flow through the gravel instead of the compost mix in cases where this becomes the path of least resistance. In both cases, tendency toward air loss can be mitigated by lining the sides and bottom of the bin with plastic sheeting. Another alternative would be to line the pallet walls with sheets of plywood. The beauty about a system like this is that you can simply and inexpensively try different combinations to determine which approach works best for you. Back to top

23. Is it beneficial during the curing stage to incorporate air into the pile?

No air is needed at this point, however, it doesn't hurt either. Back to top

24. Should we continue to monitor the temperature of the pile during the curing stage?

It is expected that the curing pile will slowly glide back to ambient temperatures. You do not need to continue monitoring. Back to top

25. What temperatures are to be expected during the curing stage?

I would expect temperatures to be somewhere in the 80 to 100 degree range, but it could be hotter or cooler depending on the ambient air temperatures and volume of the curing pile. Back to top

26. If needed, can the pile be "re-heated" to ensure the destruction of weed seeds?

Assuming that you have gone through a high-heat cycle and are in the curing phase, the pile temperatures will not come up again because there is not sufficient "food value" for the microorganisms. However, if you were to mix your compost with grass clippings (lots of nitrogen) at a 50:50 ratio, then you may be able to regain the heat needed to destroy the weed seeds. Back to top

27. My is heating up well over 131°F even before I turn on the blower. Is this a problem?

No, this is not a problem. In fact, by providing access to passive airflow at the bottom of the pile, you are facilitating a "chimney effect" which allows the hot air in the pile to rise up through the mix, pulling fresh air into the core of the pile to replenish the oxygen. This effectively "stokes" the composting process. By exceeding 131°F for three days (even prior to induced aeration) we are destroying parasites, pathogens and weed seeds. When aeration begins, the pile temperatures will drop to the ~100-120°F range, thereby expediting the composting process and producing a superior finished product. Back to top

28. Any ideas for eliminating the need to shovel the manure from the wheelbarrow into the bins?

There are three ways that folks have handled this issue.

One of our clients built a ramp that allows them to roll up and dump over the open front.
Several beta-testers have expanded the basic bin design from 4'x4' to 4'x6' to allow them to dump manure using their front-end loaders.
Several have opted for a manure bucket on a dolly that can be lifted over the top of the open side.

If you have the option of using sloping ground to your advantage, construct a simple retaining wall (even 2 to 3-feet high) and deliver the manure from the high side. Similarly, you could construct a loading dock-type platform with lumber to give you the needed elevation rise. Back to top

29. If I move a curing pile out of a bin, will the disturbance affect the final curing process?

It is a good idea to move the material to an intermediate / long-term storage area. This provides an opportunity to remix the materials and re-wet as needed. Typically, we see a slight bump in temperatures when we do this, however, I'm not certain this will happen with smaller volumes.

When moved, it is a good idea to minimize the amount of further turning because this does break up the fibrous-mesh of fungi actinomycetes (white stuff). "Do nothing" is my kind of multi-tasking. Back to top

Tell us about your project.

We will contact you to schedule a time to talk about your specific needs and to answer all of your questions about composting. We look forward to hearing from you!

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