Phil Stevens

Excess nitrogen can take different forms. Nitrate is the most common one encountered in food-growing and domestic situations, but ammonia is also an issue (think poultry litter or an overly hot compost pile). Plain biochar made from woody material is really good at mitigating ammonia and moderately good at adsorbing nitrates. The feedstock and temperature can influence nitrate mitigation potential, like using grass or crop residue instead of wood, and producing it at lower temperatures. Then there are the additives and tweaks. Iron is just one of many...clay also adds interesting qualities and enhances a lot of the filtering properties of biochar.

Without getting too far into the weeds, the main things that are happening with biochar when we try to sop up contaminants are cation exchange and functionality. Cation exchange is something that clay soils are really good at and involves negative electrical charges on the edges of the particles that attract positively charged ions when they're in solution with water. Functionality refers to the formation of organic molecule complexes (clumps) on the edges of the biochar surface structure. High functionality is something we get in lower temperature biochars, which tend to have less surface area...tradeoffs are everywhere.

Ammonium ions are positively charged, so any biochar with a decent cation exchange capacity (CEC) will soak them up. Nitrate is negative, though, so all the CEC in the world doesn't really help. But functional groups can have anion exchange potential and handle this problem. What's neat about biochar is that regardless of the material or method, after it's been in the soil for a while this property actually improves (not forever, but at least for the first several years). The other thing that's advantageous about using biochar to mitigate excess nitrogen is that it will happily give it up to plants and fungi when they need it.

r ransom wrote:

Grape
The length between the nodes is the limiting factor preparing these.  Taking the bark off is a hassle.  There is a much smaller range of thickness possible.  This year's growth is easier to cut, but it seems to make better charcoal if left to dry a few months before cutting to final length and putting in the tin.  When dry, we can roll the sticks in our hands and much of the bark comes off.  But it's not as bothersome to leave the bark on as it flakes off the charcoal when we open the tin.  

Since I have to prune this back every year, it's a renewable source.  But the extra labor of having to cut each side of the node makes prepping thismtwice as much work as willow.

Very easy to pack tight in the tin due to straight and small sticks.

Most crumbling of the charcoal so far. Lightest black.  But most neutral black, with a slight purple lean.  Smudges easily, almost to the point of erased.  

I wonder if the grape sticks could be tumbled with sand to speed up the debarking. I had a rock tumbler when I was a kid and something like this might work.

If it's something that could re-root and start growing again, make hay with it by letting it dry in the sun for several days and then use it. You'll give up a little bit of the nutrient potential, but to me that's a good tradeoff for not getting it estabilshed where you don't want it.

Encouraging, but the process looks like it requires inputs that most of us don't have. Enhanced biochars are a fascinating topic and I have a low-tech method of making magnetic biochar by treating feedstock with rust and oxalic acid. Hopefully I can get it tested soon to see how it performs (lab work is $$).

One of my biochar colleagues shared this with me earlier today. Looks like this guy has figured out an easy way to make foolproof aircrete:

You pretty much nailed it with your first question. A woodstove and an RMH are two very different animals. An RMH is a system and the stratification chamber (or mass bench, if it's an older design) is a component whose function is to accumulate the thermal energy released in the combustion chamber, store it in the mass, and release it to the space that's being heated. Very few woodstoves approach the level of complete, super-efficient combustion that you get with a properly built RMH, and so they aren't really suited to having this extra volume and mass inserted into the picture.

At best you might get a little extra "thermal flywheel" effect, but the downsides are several. You will change the draft of the stove, possibly choking it and risking smokeback and deadly CO in the living space. You will probably cool the flue gases below the condensation point and this will cause creosote deposits and raise the possibility of a chimney fire.

Your existing woodstove firebox is not designed to do what a batchbox does, so a lot of modification would be required. It might be possible to build a proper core inside of it but you'd have to be pretty fortunate if all the dimensions turned out to work.

The problem with silicone (aside from the toxic gick aspect) is that once it's on there, you'll never be able to get anything to adhere. The thing about cob is that it's super easy to patch cracks and chips, or mold new features. If you introduce a material that prevents this, you've just wrecked one of cob's best attributes.

Peter van den Berg wrote:

Glenn Herbert wrote:A J-tube with natural draft not needing the chimney warmed to burn well, I believe, could work fine in a larger bell while taking longer to store as much heat. The ISA of my bell is irrelevant to the early functioning, when any size bell would still be cold.

Forgive me Glenn, for not mentioning why the above statement won't hold, so here we go.
Of course you are entitled to believe whatever you like.
But... there is a certain effect that is firmly based on physics, the kind that won't be influenced by faith. That effect is mostly referred to as "chimney stall". About +/- 20 minutes into the burn, the exhaust gases into the chimney need to be warmer than 60 ºC (140 ºF), otherwise the chimney draw will cease to exist and all smoke will stream into the house. What I mean with temperature measurement, is done in the very center of the chimney pipe, where the stream has its highest temperature and velocity.

I stumbled upon this phenomenon many years ago and it took a lot of time to understand what the hell was happening. As you may know, combustion of woody material will produce heat (obviously), CO² and water vapor. Quite a lot of the latter, about half a liter of liquid water for every kilogram of bone dry fuel. Translated in imperial measuments: 30.5 qubic inches of water for every 2.2 lbs of dry fuel. As such, it is a by-product of the combustion process, much like natural gas. When the fuel wasn't as dry to begin with, this water content will be added to what is going into the chimney.

For now, we concentrate on the water vapor. This will be sent into the chimney and when the temperature is low enough, something between 40 and 50 ºC (104 and 122 ºF), the vapor will condensate on the chimney wall into liquid water and runs down. Lower in the chimney it's warmer, so the water evaporates again and is added to the vapor that's already there. So it rises into the chimney, but since the gasses are more saturated with water vapor now, it will condensate in an earlier state and lower in the chimney so it runs down again. This process will be repeated over and over again, consuming more and more heat, until there's no more heat to carry the vapor to the outdoors and the chimney will reach the state what we call "stall". No more draw, all smoke and water vapor is streaming into the house.
Sometimes, the stall can be deminish by itself and the draw seems to be restored. But in almost all cases, within minutes the chimney stall shows up again.

If you like to check the above explanation, extend your bell by 100%, start the thing up stone cold and watch what happens.

Thank you Peter for this explanation, which gave me a real light bulb moment. I have seen this happen several times with the little 4" J-tube in my glasshouse, when a perfect fire that has been burning for a while (usually less than an hour) suddenly goes into reverse.

A tee at the bottom of the vertical chimney would provide a way for the condensate to drain off and alleviate this problem.

Annette Jones wrote:I have to agree it's pretty weird!

Christmas Day - the middle of usually hot bush fire prone summer in Australia it actually snowed in our state of Tasmania and dropped to low autumn/winter temperatures all down our east coast.

My plants are very confused, I have shade cloth over them some hot days then the next few days frost cloth just trying for a happy medium and unaffected produce.

It's working but very labor intensive running in and out changing garden covers.

Annette, your polar blast just crossed the ditch and is over here crashing into an warm atmospheric river out of the tropics. We're about to get blasted with 120 km/h winds here. Stuff is already blowing loose and I expect some damage in the orchard. This is why I keep my fruit trees on the short side...we always seem to get a stray cyclone when the branches are loaded.

Ned Harr wrote:

Phil Stevens wrote:Chimayo would be at the top of my list. Also, there's a really pretty loop you can make over the Valle Caldera and pass through Jemez Springs.

What’s there that I should see?

The town itself is worth just taking in as an experience on its own...it's an archetypal northern NM settlement, with most of the historical bits intact, like the acequias that still carry water to fields and orchards. There's a shrine that thousands travel to every year that has dirt with reputed healing qualities, and a famous chile that the locals say is the best. It's been caught up in the tourist gentrification treadmill but the locals are trying hard to keep it authentic. They even chased off the film crew for the Milagro Beanfield War back in the '80s and forced them to shoot in Truchas instead (I had a girlfriend who had just returned from living there for a year around the time this went down and she thought it was a hoot).