Hey, folks.

After watching Robert Frost’s great presentation at the last MAPG meeting, I got to thinking (always dangerous, sometimes productive).  I had a little time to kill waiting for my son to wake up, so I grabbed some of the tin cans I’ve been saving, and tried out my idea:

I started with 2 cans, one a Progresso soup can (P), the other I think a Kirkland Campbells  soup (C).  Both are pull-top, which leave a small rim, so the C did not quite fit into the P.  I used a pair of pliers to crimp down the rim in the P can, and left 3 small flanges of the rim sticking out.  Then the C fit snugly into the P.

I then filled the inner can with the shells of the black walnuts I have been collecting, slipped the cans together, and put them on the hot coals of my woodstove.

As you can see, after just a few minutes, gasses coming from the heated shells are combusting.  The flames reduces to a small flare after only 20 minutes, and I removed the cans and set them outside to cool.

There are lots of fine flakes of biochar, and many of the larger pieces of shell are blackened, but not completely charcoal.  But I count this as a real success, I made a second one, and now have two in the stove.  I will wait at least an hour this time, rotating occasionally (the cans were glowing red on the side toward the coals.

I think I’ll fire up my digital microscope and add a pic of the fine char.  I’m going to save it in a jar to add to my garden in the spring.  I see several advantages to this method.  The mostly tight fit of the cans means no oxygen enters to allow actual combustion inside the ‘retort’.  The heat is all added to my already hot, and welcome, woodstove temperature.  The materials are very simple and available.

The quantities are small, but that makes them more manageable.  And I found almost no ash in my first ‘load’.  The second load, I left in for about 3 hours, and when finished, the can was till 1/2 full, and the shells retained their shape, but you can crush them, and they are charcoal all the way through.

The Madison Area Permaculture Guild has erected a 20′ X 40′ hoop house on the grounds of the Token Creek Eco-Inn.  As some of you may know, I put a couple of temperature loggers into the hoop house on Nov 27.  They filled up January 8, and I just downloaded their contents January 14th to look at them.

If anyone is a data geek, I can give them the original data, but it was gathered at 30-minute intervals, Temperature in Fahrenheit.  I put one in a plastic ziplock hanging on the south side of the hoop house, about 5 feet off the ground.  The other was in another ziplock laying on a stack of empty pots on the north side near the entrance. I’ve added a third now, in the shadow of a crosspiece outside on the North.

To put it in context, I played around with Weatherspark  (http://weatherspark.com) for Madison temperatures, and have put together a graphic with both at approximately the same scale for comparison.

I also had a logger (iButton) in my own little hoop, which is fairly open, it is mostly a shelter for my chickens, is about 6′ tall, 20′ long, and has about 8 square feet of hardware cloth venting, so it does not hold heat in very well.

Attached is a low resolution version of the graph.  The top is from the iButtons, the bottom from Weatherspark.  I tried to match the dates and times up, should be fairly close.  In case you can’t see it, in the Weatherspark graph, a thick horizontal line is 32 degrees, freezing.  I tried to put one in the iButton graph, but it disappeared.  The horizontal lines are, from the bottom, 20, 40, 60, 80, 100, 120, and 140 at the top.

As you can see, it got over 100 degrees on many days on one of the sensors, the other peaked at 80, with highs for one often 25 degrees higher than the other.  I forgot to mark which was which, so I would guess that the one on the south got hotter being higher off the ground and in more direct sunlight.

For the lows, note the coldest night, January 3, 6th from the right (9 degrees according to Weatherspark).  The data from the ibuttons recorded 5 and 6.8 those nights, while my hoop recorded 44 as a low that night.

We put some 55-gal water barrels on their sides, 1/2 full of water, along the south side of the hoop house inside.  I checked these, too.  There was thin ice floating on each, so the temp was probably just above freezing in the barrels.  There is snow piled up on the south side, the north is clear.

What this seems to indicate is that the hoop house has some extremes of temperature, could use some way of storing it to moderate the cold, and even out the fluctuations.  Perhaps if the barrels were further from the wall, where they are shaded by the snow, they would be warmer.

A closer look at January 2-3 shows interesting, if predictable patterns.

Here the hoizontal and vertical scale are the same, the top graph shows the sun position, next below it cloud cover, then air temperature (probably at the Airport, about 5 miles South)  Click for full image.

(I added a horizontal line at 32 degrees, and the green and blue lines are from sensors inside and outside my chicken coop at HedgeCroft)  Both the ambient temperature and the hoop house responded to the sky clearing late on the 2nd, and bumped back up with the brief cloudiness at around 7pm.  The hoop house started a quick rise in temperature just after sunrise  (there are no obstacles to the Southeast).  I have no clue why the 20 degree drop 9:30-11 AM, though I see a similar dip on many days at a similar time, maybe there is a shadow from an obstruction to the south?  I’ll look it over next time I’m out there.  If so, it would probably affect the temperature most on cloudy days.  Anyway, enough fun for now.