Thomas Vincent

I have been making biochar at home for about a year, using a two barrel “tin man” kiln. I have had good luck using primarily yardwaste for my feedstock. (dried blackberry canes and bamboo)
Recently, in an effort to spread the word on biochar, I held a free demo at a local community garden. The yard waste they had was primarily Scotch Broom. I was surprised at the amount of black smoke that came out of the vent stack. (Usually, my biochar burns produce very little smoke.) I have also read since the demo that Scotch Broom contains alkaloids and other toxins.
My questions are:

a. does combustion or pyrolysis from toxic or sappy plants release any harmful toxins into the atmosphere?
c. Do any toxins in plants survive pyrolysis or combustion and persist, thus spoiling the resulting biochar?

Thoughts?

T. Vincent
Langley, WA

Whenever I have an electronic gizmo that can’t be repaired I put it in a box. When the box is full I take it to an artist friend of mine who takes the machines apart and uses the innards - copper wire, transistors, etc. in her latest piece of art.

Recently I was searching for a small container to make biochar in. At the dump I found a large coffee urn. Looked like aluminum, drilled like aluminum. Great. Took the plastic off, filled it with organic material and threw it in my burn barrel. When I opened the barrel later this is what I found.

Pretty artistic.

I added a second layer of poly to my small hoop house this winter and it worked quite well. Check out my blog post if you are interested in details.
https://tinkersblessing.com/2017/11/17/double-wall-hoop-house-results/

T. Vincent

Thanks to one an all for your replies. They were all helpful in elevating my understanding of thermal mass, what it can do and what it cannot.

The following is a reprint of my response to another hoophouse forum here on permies.

I have completed adding a second layer of plastic on my cattle panel hoop house. Added a total of 190 gallons of water (milk jugs and 3 55 gal drums.) all painted black. Finished it off with pallet counters covered in terra-cotta tiles. (See pictures)

At the end of a miserable cold and rainy week here in the Pacific NW with an average daily outdoor temp of 45 degrees F., the average daily interior temp was 51.8!
Even better, the interior temp At sunrise was always at least two or three degrees higher than outside. This is all I was really after so I consider this experiment to be a success.

Not sure how much of this improvement was due to the extra plastic (insulation) and how much due to the added water (thermal mass), because I added both at the same time, but I think I can state pretty conclusively that double walled hoop houses with significant amounts of thermal mass can create a better growing environment in winter in the Maritime Northwest, without the use of fossil fuels, than occurs outdoors.

Now I just have to tackle that pesky "lack of sunlight in winter" problem! 😄

PS I will be posting full results on this hoophouse along with my experiments making biochar at my blog: tinkersblessing.com

Scott,

On the off chance you are still monitoring this here's an update on my hoophouse project.

I have completed adding a second layer of plastic on my cattle panel hoop house. Added a total of 190 gallons of water (milk jugs and 3 55 gal drums.) all painted black. Finished it off with pallet counters covered in terra-cotta tiles.

At the end of a miserable cold and rainy week here in the Pacific NW with an average outdoor temp of 45 degrees, the average interior temp was 51.8!
Even better, the interior temp At sunrise was always at least two or three degrees higher than outside.

Not sure how much of this improvement was due to the plastic and how much due to the added mass, but I think I can state pretty conclusively that double walled hoop houses do create a better growing environment in winter in the Maritime Northwest.

Todd,

Thanks, that was very helpful.

One geeky question and then I'm done. When the barrels of water absorb heat on sunny days, is it only radiant heat from the sun - heat that would otherwise add to the temperature of the space - or are the barrels only absorbing heat from the room itself? (By convection?)

Thanks to everyone.

Thanks for the replies. I'm still a little fogged here. Let me restate the question:

I have a standard cattle panel hoop house measuring 6 feet by 15 feet. (90 sq ft) Winter and summer, on sunny days the interior temperature is a full thirty degrees warmer than outside. If I add four fifty gallon drums of water, (200 gallons) to the interior will that mass affect the interior temperature of the hoop house when the sun shines. And if so, how?

In other words, if I simply add thermal mass to the interior of a green house can I expect to see any difference in the temperature differential between Outside and inside on sunny days?

Thanks.

Ok I have to admit I don't really understand the concept of thermal mass in passive solar design. Most of the books and videos on the topic say that adding large volumes of water - like 55 gallon drums painted black - will store heat that will be released as the temperature inside the greenhouse drops thus keeping the space warmer. I have no problem understanding how the sun can warm the drums and cause them to heat up. And warm barrels releasing heat to the cooler air is also easy to understand.

But designers also talk about solar collectors which are basically insulated boxes painted black and glazed on one side. These are supposed to get super hot when the sun shines.

My question is: So wouldn't the addition of lots of black surface area inside your greenhouse cause the interior temperature to rise more during the day than if they weren't there? In other words, how come the black barrels don't turn your hoop house into an oven?

Any physicists out there care to take a crack at answering this one?

Mystery of the hoop house temperatures solved.

Sometimes things are so simple you can't believe it. I had an old bulb thermometer in the hoop house. I bought another of the same brand to compare outside and inside temps. Same thermometer = fair comparison, right? Wrong! The older bulb thermometer had slipped in its housing giving a false reading. Doh!

Okay, this one's for anyone who's still following this thread. Yesterday I finished adding a second layer of plastic to my cattle panel hoop house. Spent two hours sealing up the seams. Still not hermetically sealed but reasonable. This morning I come out. Seven thirty AM, overcast, outside temp is 41 degrees F inside temp is 39 degrees! It's actually colder inside than outside! .

It's sure got me stumped.
Thoughts?