Hi Peter… I’ve been doing some more reading on your system because I think it is a great concept for our stables. I have questions/concerns about our severe winters. Specifically, I’m wondering about: 77″ of snow thsi year and -40 degrees a couple days. It is very typical to have -0 nights and highs in the single digits for 2 months of winter. The ground is frozen fro 6 months out of the year.

Does frozen manure work in the system? Even our stall manure is frozen in the middle of winter. How do bays get “cleaned” in between batches? How long is the complete process from fresh to cured in 10 degree weather? Does the finished product freeze solid in the bay?

Peter’s Response to Jolene’s Email:

Jolene… This is an excellent set of questions. Up until a year ago, I wouldn’t be sure how to answer them however we’ve been working with a client in Morrisville Vermont who experienced these same conditions and we “redesigned” her system for extreme cold and this year all went quite well.

First, our systems use post and beam construction. For each bay, we place boards (e.g. tongue and groove 2 x 6’s) on each side of the posts to create double wall configuration. We then fill the hollow space with insulation. This can consist of foam board; spray-in, expandable foam; vermiculite pellets, etc. Finally, we place a 2 x 10 cap on top of the wall to seal in the material.

Second, we construct light weight, removable, insulated panels for the front to prevent excessive heat loss through the slide boards. These panels may be constructed using 2 x 2’s and thin plywood on each side (much like a hollow core door), again with insulation on the inside. We would use these panels only during the extreme cold periods.

Third, we place an insulated cover over the top of the bay when it is full. We have played with a vareity of designs, but a simple one consists of two layers of poly-tarp with flexible insulation sandwiched in between. We use grommets to create a single unit. This is light weight and easy to handle.

Finally, prior to filling the bay, we coil a 48-foot length of heat cable on the slatted floor (these are inexpensive and available on the internet through a variety of greenhouse suppliers). This acts just like a block heater for your car.

Operationally, you do your daily chores removing the manure and bedding from the barn and fililng the bay. Everything can be frozen solid – not a problem. When the bay is full, we plug in the heat cable and allow it to thaw out the core of the pile over a few days and once the core of the pile is up to 60 or 70 degrees (max for the heat cable), the biology will take over and bring the pile temperature up to the desired levels.

One key is to minimize aeration so that we don’t cool the pile excessively and, more importantly, so that we don’t dry out the material to the point where the biologic process crashes.

The second key is to not let the compost stay in the bay too long. Generally, the process is roughly 30 days long, but it is okay to cut it short so that we can remove the mostly-composted material from the bay before it returns to a frozen condition.

In designing the system, you may also consider over-sizing it somewhat so that you can receive the raw manure, compost it, and then allow it to cure / store in the same bay until the spring time. This obviously results in a larger system and will cost more, but it may also be worth the convenience of not having to move material when it is well below zero.

PM

I built three insulated bins that have an R factor of about 20 or so. This has been allowing us to keep our manure composting when the temperature hits single digits and we had heavy winds for a couple of weeks.  Because our bins are heavy and permanent, I set them up a bit differently. You can see how I plumbed them in the attached pictures.

The bin on the left is full and running over 100 degrees (it is on the downside of the composting temperature curve). I have loose hay on top for some insulation and then some wire screening and boards to hold a tar paper cover off the manure and allow it to vent air when the fan is on. The right bin is full of hard frozen manure waiting to melt. And the middle bin is about 1/3 full of frozen manure.

We do have a few problems. One of the biggest is that we have been collecting manure that is frozen very hard. Getting this to start composting may not be possible until spring, but it sure would be nice to get it started earlier. So we have had an unusual warm spell for the last 2 days and I have been blasting warm, wet air into the frozen bins. I think this is working as it is beginning to settle. In a couple more days, I may have it running. But I need a better insulating blanket on top. I have used hay and leaves for top insulation and both get wet from condensation and compact – which seals off the air flow. I think something like a quilt made from loose weave plastic burlap or even some sort of netting and filled with crushed Styrofoam packing peanuts might keep in the heat fairly well while allowing air and moisture out. What ever it is, it has to breathe, be impervious to water, and not freeze stiff when wet and cold. I haven’t found the ideal material yet, but I will eventually. If I was really smart, I would also figure out how to run the excess heat from one bin into a frozen bin to get it started. I can imagine how to do this, although it would be a bit of a plumbing nightmare. In any event, this is our operation, and it works quite well. Thanks for getting us started on this.

Comment from Peter: Last winter I had a similar problem in NH with frozen manure being delivered to the compost system and then not thawing out during periods of extreme cold weather (logically). We recommended that our client use heat cables from the greenhouse industry to get the core temperature up to ~70 degrees F to kick start the biology. These are much like block heaters for your car. They are inexpensive and I think will work quite well in your application. As for a cover, I suggest using 2-3 foam board cut to fit with small gaps between individual panels. You can lay on top of these and then bungee cord them into place. These would be inexpensive, easy to handle, and quite effective – at least in concept.