Phil Stevens

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.

You can try. I've righted lots of downed trees and nearly every one of them survived. The good news with this one is that it's only leaning and not flat on the ground.

Step one is to reduce the crown. There are a few reasons for doing this. One is to lower the transpiration rate of the tree, since it's under stress from some of its roots being snapped. Another is to limit the amount of profile it presents to the wind and make it less likely to get blown down again. The last main reason is to make it weigh less so that it's easier to winch back upright.

I'd advise cutting back about half the length of all the branches, and maybe doing a bit of thinning so that the canopy is less dense. When that's done, it's just a matter of using a winch, block and tackle, or similar contraption to gently bring it back upright. You might need to prop it for a season while it regrows some anchoring roots. Three stout poles, equidistant from the trunk, can give you a place to tie off some straps with give in them. r ransom cleverly suggested inner tubes.

I've got two mature ones in the "pretty" gardens up by the house. They have both tended to have very sparse, open canopies and a habit of dropping branches, so I never really did anything to them.

Until we had a hellacious windstorm right before new year's. Two straight days of gale easterlies, including most of a day out of the NE, which is a quarter we rarely see any wind come from. The bigger tree got wrenched out of the ground and tossed in a heap. I wasn't prepared to write it off completely, since it was the kids' swing and climbing tree, so I cut it back to just the trunk, and used a block and tackle plus a hi-lift and some stout timber props to hoist it back up to something resembling vertical.

[edit to add] For an idea of the physics involved in how this tree went down, the direction of the fall is directly into the strongest winds. This is a really sheltered spot, with tall trees all around, so I can only imagine how some combination of turbulence and possibly a few intense downdrafts must have twisted the crown and uncrewed the base of the tree from the ground.

After bucking, splitting, and stacking, I estimated half a cube of firewood for my time and trouble. It's a dense wood, like lots of legumes, so I expect it will have a lot of heat value. Really attractive colouring and figure, too...reminiscent of mesquite and Tasmanian blackwood. The tree started putting out new growth within a month and now has a few clusters of shoots. It's dropped most of its leaves now and gone dormant for the winter, so I'll keep my fingers crossed for a resurgence in the spring. There's a big dead/rotting strip running up one side of the trunk, so it might be on borrowed time anyway. If that's the case, I have allowed one root sucker to come up and if the original stem packs it in, there's a replacement right next to it.

I've had a greenhouse for ten years now and I can easily identify the three limiting factors working against productivity in the winter months. Heat is the least of my worries, since the climate here is so mild. I can run the RMH on cold nights and keep the temperature well above freezing despite the single layer of thin glass radiating all the heat away.

The bigger issues I need to solve if I want to get a better yield are humidity control and light. Even though I cut back on watering in the cooler months, the inside of the glasshouse is close to saturation most of the time. I have to remember to open things up in late morning and close it down by midafternoon to air it out, and even with this habit a lot of plants suffer from fungal and bacterial incursions. I've been brainstorming some sort of air exchange that will help mitigate this.

Light levels are the other major limiting factor. No point trying to grow warm-season crops under glass if they're only getting a few hours of sunshine at best, and little or none on cloudy days. So I need to put in LEDs for augmentation purposes, and then dedicate a power source with enough headroom to get through a week of stormy weather. Bonus points if this setup can also drive a bit of active air circulation to help me get on top of the humidity situation.