Phil Stevens

Willows are my "carbon crop" trees. I coppice and pollard them, using the poles for garden stakes and biochar, with the added benefit of fodder for the sheep. I can either feed them directly if I cut in the summer or early autumn for drought fodder, or dry them for tree hay to feed out during winter. For actual firewood, I like Tasmanian blackwood (Acacia melanoxylon) because it comes up from root suckers without being planted (could be weedy but hasn't been trouble here), grows fast, fixes nitrogen, pollards and coppices fairly reliably, yields a dense, high-heat fuel, and plays nicely with surrounding trees.

r ransom wrote:I just discovered bardcore - it's like medieval music, but with a modern bend.

The songs can be pretty fun.

Paint it black, but make it more medieval

That was just what I needed on a stormy morning. The ending gets very Carmina Burana-ish, which took me to this wonderful digression:




Back to proper bardcore, though...I went looking for Kashmir and came up empty. Might have to put this in the project queue. But this one is so, so good:

Biochar pH is going to be a function of two main variables: Feedstock mineral content, and highest treatment temperature. Hardwoods tend to have more minerals than coniferous species, so the biochar will have more embodied ash and a correspondingly higher pH. Softwoods like pine and fir don't produce nearly as much ash and yield a more neutral or even acidic biochar.

At lower temperatures, the reactions of pyrolysis form various hydrocarbons that bond to the carbon molecules of the char substrate. These are reactive, often acidic, and tend to lower the pH of the biochar. Higher process temperatures destroy most of these substances and leave behind more pure nonreactive carbon along with the minerals, so the resulting biochar will be more alkaline.

I'm a little surprised at that cited article's claim that charcoal is higher in pH. I would expect products made at low temperatures (to retain more of the hydrocarbons for easy lighting and greater heat value) to be more acidic in the same way biochar is. Also, the realistic range for biochar production is more like 350-750 C. Below that the pores are plugged, and once you get around 800 degrees the structure turns to graphene sheets and porosity decreases due to the flattening effect.

If you're trying to fix acidic soils, go for hardwoods and high temperatures. If your soils are alkaline (or you're growing acid-loving plants) then stick to conifers and keep the temps down. Post-treatment like composting or washing with rainwater will also lower the pH of the finished product.

I just watched a PBS documentary on the January 2025 fires in LA, looking at the response a year later and doing some deep analysis of what could have been done to protect the communities that burned. The biggest bang for the buck, stressed again and again, was fireproofing the properties and structures, pretty much along the lines of all the good advice that's been coming out in this thread. There were a few major points that might not have been intuitive to those of us that haven't been through a massive wildfire:

It's much, MUCH harder to fight a fire once it has transitioned from wildland to the built environment. One house in an urban setting takes 10-15 people and 2-3 appliances to successfully extinguish...if the winds are high or water unavailable, they can't be expected to save it. And if the houses around it don't have a fully hardened perimeter, they are even more likely to catch. and now the equipment and people requirement is multiplied by the number of houses involved.

In high wind events, all bets are off. Wind-blown embers can travel hundreds of metres ahead of the flame front, and they get driven into all sorts of places that allow them to kindle new fires. Vents, gutters, shutters, any sort of gap that leads to fuel is a hazard.

Even if there's an ample water supply and hydrants, as soon as a lot of houses have burned then each one of them will have its supply connection running full blast because the internal plumbing is destroyed. Add those together and you get a significant pressure drop, coupled with the loss of supply that's now just running down the streets.

William Bronson wrote:
Phil, rather than a batch box rocket stove to provide heat to your retort,consider a sawdust stove.
They are cheaper and simpler to build, they can burn many hours without any human intervention and the fuel is tight there at your fingertips.

I'd like to do that, because there is a MOUNTAIN of nice clean sawdust. Problem is, it's outdoors and it rains a lot here. Sawdust stoves are dependent on dry fuel, just like a TLUD...I saw one barrel full of wood pellets grind to a smoky halt when the flame front hit a wet zone.

So it looks like I'm destined to go down the track of a monster batch box. Peter's got a chart of dimensions that go up to a system size of 250 mm (10 inch) and I think that will pump out enough heat to get a 1.5 - 2 m3 retort cooking. Apparently someone in Argentina has built one this size, so maybe I'll try to get in touch for some tips.

I've been making lots of biochar at a nearby sawmilling yard. I went by to talk with the owner the other day and his main bottleneck has become the time it takes for rough-sawn boards to air dry enough that he can send them for dressing and treatment. So we're now contemplating building a retort that will be powered by a BIG batchbox and then take the exhaust from the process and blow it into a container to make a simple kiln.

Which leads to the obvious question: what is the biggest batchbox that has been built and proven to work reliably? What sort of thermal output does it provide? I'm seriously thinking about a 300 mm (12-inch) system.

I get these from time to time. Never enough to drag out the heavy artillery, but if I did feel the need to intervene I would probably try soap, and then maybe dilute wood vinegar. They are annoying and nothing seems to want to eat them.

It's definitely got a mad scientist vibe to it. I don't know if I would trust the braking and holding features in the sort of storm winds we can get here.

It's always cool to see someone finding a way to exploit marginal resources. But the problem is just that: they're marginal. Low speed means low power unless you make up for it with massive flow by having a huge swept area. A small turbine (strike one - low swept area), close to the ground (strike two - boundary effect and friction decreasing wind energy), in a residential setting (strike three - buildings and vegetation nearby causing turbulence and dissipating the wind) is chasing poor returns. This inventor is at least only contending with two of those in his demo, since the wind across a body of water will be mostly unimpeded.

Solar and battery has become so cheap now that there are only a few edge cases where it's not the obvious choice hands down. Obviously, winter in high latitudes is one, but if the primary need is heat then wood makes more sense anyway. And sites with simple hydro close at hand are hard to beat, but they're not all that plentiful. I get the attraction of homegrown tech, but panels with a 50 - 75-year effective lifespan can be viewed as a one-time investment and you could roll your own battery and electronics if you were really motivated.

Judith Browning wrote:
Phil, I'm not sure I've ever seen a mimosa that large😯

Steve has carved spoons out of small pieces and says it's a little soft compared to some woods and looks like fudge ripple ice cream.  We don't see very large ones here.

It's only 25-30 years old, tops. Some trees grow insanely fast here, like the English oak that's a similar age and almost 15 m tall with a trunk that I can't even begin to wrap my arms around. The wood felt really dense as I was cutting and splitting, but as far as the chainsaw response goes, it's definitely not as hard as the desert legumes or our native kowhai. I'll know in another month or so what it's like in terms of heat, since it's at the back of the wood pile.