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Biochar producing wood stove

 
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I know this isn't about RMHs, but i'm looking to get a wider opinion, and i know this forum sees a decent amount of traffic, so please move it if you feel its inappropriate.

I've been interested in the idea of biochar for some time, i know others are as well either for garden applications, some people for charcoal gasification. The process of making it however is ever so wasteful. The most useful way ive found is putting a tin can in the woodstove in order to capture the heat giving off in the biochar producing process. This however yields such small amounts of biochar, which is why inevitably people tend to switch over to the most wasteful production methods in the end.

For a while now i've been throwing around the idea in my head of producing a type of wood stove that can take full sized firewood splits and turn all or most of it into biochar, while at the same time heating your home or space.

However it seems the more i think about it the more discouraged i get about the idea, convincing myself nobody would be interested in it. I think that people won't want to deal with the inconvenience of removing the char out of the stove after the burn is complete, or that they won't like the idea of a 30% reduced burn time. Charcoal makes up about one 1/3rd of the weight of a piece of wood, no naturally even in an efficient design your burn times will only be 66% what they would be if burning the entire piece of wood including the charcoal.

My other big reason for doing this, is that my province in canada has come out with the plan of banning wood and pellet heat by the year 2030 as part of their climate change fighting effort. Not only wood and pellet, they wish to also ban all natural gas and propane appliances also, everything will be ele tric. This made me extremely sad and even a little angry, the cost of living recently has absolutely skyrocketed, energy prices have soared, and here they are going to take away the only affordable means of heating our homes in the harsh canadian winters. You can bet that electricity prices will increase exponentially by the time we are all forced to make the switch.

That brings me to my other reasoning for this idea, the biochar process i've seen has been considered a carbon negative process. A dead tree left to rot in the forest will eventually decompose into CO2. If biochar is made from that tree and subsequently buried in the garden, it will take 100s of years or more for that char to decompose into CO2. This means you can still capture the heating value of dead wood and biomass, without the huge release of CO2 in the process.

I know it may not be perfect, but my thinking is a system can be built that still allows us to cheaply heat our homes and in the process combat climate change, then surely it must be worth it. Because at the end of the day as much as many people wish to do good for the environment, sky high costs of heating will make it harder to live than it already is, and i feel horrible that there isnt something we can do to satisfy both needs.

Anyway, thats my long rant. Please let me know what you think. Is this endeavour worth it? Do the pros outweigh the cons? Or should i save my time and money and pick a new dream to follow?

Thank you for your time.
 
pollinator
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my province in canada has come out with the plan of banning wood and pellet heat by the year 2030 as part of their climate change fighting effort. Not only wood and pellet, they wish to also ban all natural gas and propane appliances also, everything will be electric.


Justin, I really think you need to get involved with a political program to prevent that law progressing.
I cannot think of a worse country to even think about a law like that.
I can only think it has not been clearly thought out, plus it may have some vested interests behind it.
There are far more issues that would work better than a ban on heating with wood.
In Australia we are swinging into wind and solar, encouraged by favorable tax changes which means we have foreign
control of our energy system.
But at least we have sun as an alternative. What has Canada got as an alternative?
 
Justin Hadden
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Hi John, yes it's quite a frightening proposition. It definitely has not been thought through properly. Between these goals to make a certain percentage of cars all electric and now the push to make all heat and hot water systems electric as well, the demand on the power grid will be absolutely enormous come winter time in the future.

The other scary thing that has to be considered is that not only would this increase the likelyhood of rolling blackouts due to shear demand on the electrical grid, but we are also not strangers up here to having power outages in bad winter weather already due to ice, snow, car accidents that take out power poles. Should you lose power in minus 30 degrees celcius and your main heat source is electric, the very real possibility of freezing to death will arise.

What i would like to do is try to develop some sort of wood and or pellet heating system like I described before and possibly bring it to the provincial government as an alternative to their proposed ban on wood heating appliances.
 
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Justin, I follow local, provincial, national, and international news pretty closely. What you are saying is (wait for it!) news to me. Can you give some details? If it's a link to a published plan, it's not automatically political.

EDIT: Whoops, on second thought this does encourage a political food-fight. Which our moderators could do without. If you have a link, send me a PM.

All wood stoves, if they are truly airtight, can create biochar: once the tars in the charcoal have burned out, you close the draft and go to bed. But as you say, it's messy business and will be a hard sell to anyone who is not a biochar nut like the folks you'll see here. I think the easiest location for a biochar-making wood stove is outdoors -- an auger system could move the charcoal into a curing chamber to finish offgassing with heat but not oxygen. I don't see this scaling into the suburbs though.
 
John C Daley
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Justin, any wood burning device is still using wood!
In your environment alternatives are a 'death trap' if 100% availability is not going to happen.
Will the politicians sign that guarantee? I doubt it.
 
John C Daley
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I found this;
Are wood stoves going to be banned in Canada?
Public health says fireplaces are the leading cause of poor air quality days .
The city of Montreal plans to adopt a bylaw forcing residents to remove wood burning stoves and fireplaces by December 31, 2020.
Vancouver Metro has a similar plan for 2021
The Feds have this in place;
Wood stoves will not be banned, as long as the stove being purchased is an Ecodesign model or was manufactured before the 1st January 2022.

I think your original statement may be incorrect, but I have seen similar laws around the world for cleaner burning units.
 
Justin Hadden
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I'll tryto dig up what i was reading.
 
Justin Hadden
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John C Daley wrote:
I think your original statement may be incorrect, but I have seen similar laws around the world for cleaner burning units.




https://www.google.com/url?sa=t&source=web&rct=j&url=https://www2.gov.bc.ca/assets/gov/environment/climate-change/action/cleanbc/cleanbc_roadmap_2030.pdf&ved=2ahUKEwiV25qCq4P7AhVAFTQIHQUWBTwQjBB6BAgPEAM&usg=AOvVaw1pAC33eQRGDnVMa9bBS6_O

Its a long read, but if you skip down to page 40 and start reading there, it says "after 2030, all space and water heating appliances sold and installed in BC will be 100% efficient."

So you have to read between the lines, no combustions technology, whether wood, pellet, or gas can ever acheive 100% efficiency. The only truly 100% efficient systems are electric. Electric resistance heat converts 100% of its input energy into heat. Its a terribly difficult way to heat a space, but on paper i guess to them it looks good. The other funny thing is if you were to trace back all the way to the power plant (which is combustion technogy) then its probably even a less efficient process to heat my home electrically then it would be to simply have a wood stove in my home.

If you contjnue reading i believe on page 42 it talks about giving labels to everyones homes and giving it a carbon footprint rating for sales purposes. Meaning if some career political wannabe in a suit decides he doesnt like the way my household heats or cools or whatever they can give me a rating that will seriously affect my sales price.

Unfortunately with these things the government will hide the agenda deep in the text, i suspect as a way to avoid pushback. That seems to me to be exactly whatthe government of British Columbia are doing. Bury it in a massive document, and then most people will be taken by surprise by the time it comes to pass.
 
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I’ve thought about building such a stove.  Probably won’t happen though, too many projects already.  I would like to see someone else do it!
 
pollinator
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Justin Hadden wrote:I know this isn't about RMHs, but i'm looking to get a wider opinion, and i know this forum sees a decent amount of traffic, so please move it if you feel its inappropriate.

I've been interested in the idea of biochar for some time, i know others are as well either for garden applications, some people for charcoal gasification. The process of making it however is ever so wasteful. The most useful way ive found is putting a tin can in the woodstove in order to capture the heat giving off in the biochar producing process. This however yields such small amounts of biochar, which is why inevitably people tend to switch over to the most wasteful production methods in the end.

For a while now i've been throwing around the idea in my head of producing a type of wood stove that can take full sized firewood splits and turn all or most of it into biochar, while at the same time heating your home or space.

However it seems the more i think about it the more discouraged i get about the idea, convincing myself nobody would be interested in it. I think that people won't want to deal with the inconvenience of removing the char out of the stove after the burn is complete, or that they won't like the idea of a 30% reduced burn time. Charcoal makes up about one 1/3rd of the weight of a piece of wood, no naturally even in an efficient design your burn times will only be 66% what they would be if burning the entire piece of wood including the charcoal.

My other big reason for doing this, is that my province in canada has come out with the plan of banning wood and pellet heat by the year 2030 as part of their climate change fighting effort. Not only wood and pellet, they wish to also ban all natural gas and propane appliances also, everything will be ele tric. This made me extremely sad and even a little angry, the cost of living recently has absolutely skyrocketed, energy prices have soared, and here they are going to take away the only affordable means of heating our homes in the harsh canadian winters. You can bet that electricity prices will increase exponentially by the time we are all forced to make the switch.

That brings me to my other reasoning for this idea, the biochar process i've seen has been considered a carbon negative process. A dead tree left to rot in the forest will eventually decompose into CO2. If biochar is made from that tree and subsequently buried in the garden, it will take 100s of years or more for that char to decompose into CO2. This means you can still capture the heating value of dead wood and biomass, without the huge release of CO2 in the process.

I know it may not be perfect, but my thinking is a system can be built that still allows us to cheaply heat our homes and in the process combat climate change, then surely it must be worth it. Because at the end of the day as much as many people wish to do good for the environment, sky high costs of heating will make it harder to live than it already is, and i feel horrible that there isnt something we can do to satisfy both needs.

Anyway, thats my long rant. Please let me know what you think. Is this endeavour worth it? Do the pros outweigh the cons? Or should i save my time and money and pick a new dream to follow?

Thank you for your time.

Hi Justin,
First off which Province are you in. I've heard of urban bans but province wide? I don't deny they could try but succeed?
Anyways, When I made charcoal for my gasifiers I would make it in the woodstove. You don't even need a metal container as they wear out. Its messier this way but works great. A friend of mine used his outdoor wood furnace the same way with much higher quantities. I've gone the high efficiency route myself with an all electric energy super efficient home but wood is still in my blood.
 
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I saw a rough prototype at the MREA energy fair in central WI this summer.  The gentleman seemed like he was tinkering with it and not pursuing an EPA certified design by any means.

It was a 55 gallon drum on its side as the stove.  Inside it on spacers fit a smaller drum.  His was around 30 gallons but he said that was too big.  That smaller drum would be swapped out once the contents had turned to char.  The small drum, I think, had a pipe to exhaust the wood gasses into the larger stove to ignite and keep the fire going.

I believe as we talked the thought was to offset the small drum higher within the big drum to give more space for building the starter fire.  You need a fair bit of fire to get the char barrel cooking out its wood gas.
 
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I've seen some pretty big outdoor wood boilers heating residential properties in cold climates.  I bet you could load a stainless steel drum through the front door, fill that with wood to char, then fill the remainder of the firebox with full-combustion wood.  At the end of each burn cycle, you'd just have a barrel full of char to collect.  That would solve the scaling-up issue.
 
pollinator
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For years I’ve been playing around with a rockety charcoal making stove.

I’ve had pretty extensive use of rocket style cook stoves, fed with twigs. We use them camping and out in the woods. They rely on flames, and tend to build up a decent thickness of embers over 30 minutes of use. This gets problematic as the embers actually clog the airflow for the flames, but you need to keep some in there to kindle the next set of twigs.

I’ve previously scraped them out of the burn tunnel and dumped them beside where I’m cooking. Yield isn’t great but it is non-negligible.

My thinking is that a burner designed on these lines, but with a dead end cylinder directly beneath a grill at the bottom of the burn chamber would build up a thick layer of chars over time. And those chars would be protected by the overhead flame front.

Scale the whole cook stove up to something about the diameter of paint tin, and you could run a substantially larger stove in a similar manner, dumping coal and ashes below as they form.

It wouldn’t be particularly efficient burning - you’d get plenty of ash formation. But if your primary aim was eg heating your domestic water for an hour once per day, it could be an interesting secondary yield.

My big concern about a domestic/indoor stove design would be the carbon monoxide risk. As the fire goes out and dies down you have partially smothered hot embers with no clear ventilation route. I can’t see how any such continuous feed system can operate without tackling those risks.

I’ve also thought for a while about just shovelling a few embers out into a tin at the end of each evening… but again, I’d end up with smoke and potentially CO in the house. I’d have to immediately take it outdoors to quench. In practice I’m unlikely to do that right before bed each evening.
 
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If i understood right, rmh is burning with as much oxygen inflow as possible. A bio char container ils burning with as little oxygèn inflow as possible.
I would not like to have a stove in my house creating char coal because it creates lots of CO. A dangerous gas.
Maybe thé path forward is grow more CO2 trapping trèes in thé world.
 
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Michael,  you are blowing my mind.
Just yesterday I was going to post asking if anyone had done something like this!

Add water to the dead end cylinder and I think the danger goes away.
The coals fall through the grate and are doused in the water below.
That cylinder of water could be any size, even a  55 gallon drum.
One of Uncle Muds inside a barrel cottage rockets, with a grate at the bottom of the feed tube,  sitting on top of a 55 gallon of barrel of water,  is pretty much what I'm thinking of.

The water in the tank could get rather basic, with the ashes being added, so refreshing the char and ashe suffused water will be a good idea.
 
Michael Cox
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Hugo Morvan wrote:If i understood right, rmh is burning with as much oxygen inflow as possible. A bio char container ils burning with as little oxygèn inflow as possible.



Not necessarily. You just need different regions of the burner to have different oxygen ratios. This is how flame cap biochar systems work (eg the "cone kiln"). Provided you keep adding fresh fuel and maintain the flame-front the oxygen doesn't reach the embers. In this context you probably also need to physically separate the regions, as the rapid airflow of a rockety type burner will probably overwhelm the flame front.

There are definitely design problems to be resolved.
 
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Justin - which province are you in?
I've been thinking king along similar lines.
I made a char cooker out of a 45 gal barrel and some steel doors, using the gasses to finish the process.
When I saw how much heat was coming off it, I thought I should be making g mybiochar in winter when the heat could be usedas well as the biochar.

I'm currently thinking of a greenhouse with a (rocket?) Biochar stove that I would run on the colder nights.

Hoping to have time this winter to work on the design.
 
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Justin,
This idea is basically the Holy Grail of biochar design.  Many of us have commented on wanting to find a way to make these things happen in the same device.  I am currently using a 55 gallon TLUD, which makes enough really good biochar, but I haven't found a way to use the heat.  I think rocket mass heaters are going to be a way to do that, but I'm not as advanced in building machine systems as many on this list.  

I would think that rocket mass heaters are going to be a way for rural Canadians and those in the Northern and Eastern US to heat their homes. When they are well built, they release almost no pollution and heat very efficiently.

This idea was featured in the award winning film, "The Need To Grow", which I think is still available to watch for free.  
https://grow.foodrevolution.org/?orid=174172&opid=314

I believe that there will be a huge future in the cross pollinating and inventions in these areas.

John S
PDX OR
 
William Bronson
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Martijn Jager,  the creator of the Permaculture Playground channel, has plans for an Indoor charcoal producing tlud stove.
Here are some l8nks to his work:
https://permies.com/t/170631/Indoor-biochar-producing-TLUD-gasifier

https://permies.com/t/89764/Indoor-biochar-producing-TLUD-gasifier


 https://www.youtube.com/channel/UCeQm1gVoNMVpyFcWHKqFB2w/videos  
 
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I have been thinking along these lines, too. We've been making char using the trench method, and all that wasted heat hurts my heart.

Maybe what I've been thinking is similar to what Michael describes. Or maybe I've got it all wrong, since I'm new to stove design... Anyway, I imagine a system where the gases are burnt RMHish (=efficient) but the "floor" of the burn chamber is a very coarse grating, with the grate bars running perpendicular to the direction of the firewood pieces. Once a piece of wood is burnt enough to crack into segments (that is, when it's charred) it would fall through the grating. The pieces would then roll down an incline (preferably directed inwards in the stove) and fall through a smaller opening down to the char-holding container.

At first I was thinking of putting water in the holding container to extinguish the embers straight away, but I'm thinking that would a) make damp rise, which would cool the burn chamber and make the burn less efficient, and b) stop after-charring of any remaining unburnt pieces. The point of the pieces falling through a small hole is twofold: restricting oxygen access to the char in the container and direct the pyrolysis gases into the junction between burn chamber and heat riser, so there is less risk of carbon monoxide poisoning from gases going the wrong way. The char holding container would have to be periodically emptied into a bucket of water, and it'd have to be mostly airtight except for the hole the char enters through, so I'm not altogether sure how to conveniently empty it...

Does this sound like anything approaching functional, or would it be a huge disaster?

Also, we have been doing most of our cooking this past summer on a rocket-type stove, and we, too, have harvested a decent amount of char as a by-product (though probably not as much as from one single trench burn!)
 
Douglas Alpenstock
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Hmm! I have seen a lot of antique coal/wood stoves with a geared system at the bottom that macerated ashes (powered by a hand crank), moving them to the ash box. With very little modification, I'm sure the ash box could be sealed from air incursion.

I wonder if this old but effective technology, based on coal and with infinite hours of practical testing, might be adapted to serve new objectives. Wouldn't that be cool?!
 
Eino Kenttä
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Douglas Alpenstock wrote:Hmm! I have seen a lot of antique coal/wood stoves with a geared system at the bottom that macerated ashes (powered by a hand crank), moving them to the ash box. With very little modification, I'm sure the ash box could be sealed from air incursion.

I wonder if this old but effective technology, based on coal and with infinite hours of practical testing, might be adapted to serve new objectives. Wouldn't that be cool?!


Ooh, that sounds really neat! Do you have a picture of such a device by any chance? I've never heard of them.
 
Douglas Alpenstock
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This is the only image I could find. It gives you the idea. Most antique cookstoves had them, but they're hidden behind a door.

 
William Bronson
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Hers an outdoor tlud set up for cooking:
https://youtu.be/0ufIDYfbU7A
 
William Bronson
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Eino Kenttä wrote:

At first I was thinking of putting water in the holding container to extinguish the embers straight away, but I'm thinking that would a) make damp rise, which would cool the burn chamber and make the burn less efficient, and b) stop after-charring of any remaining unburnt pieces. The point of the pieces falling through a small hole is twofold: restricting oxygen access to the char in the container and direct the pyrolysis gases into the junction between burn chamber and heat riser, so there is less risk of carbon monoxide poisoning from gases going the wrong way. The char holding container would have to be periodically emptied into a bucket of water, and it'd have to be mostly airtight except for the hole the char enters through, so I'm not altogether sure how to conveniently empty it...



For what it is worth the times I've doused a trench of charcoal from the bottom up, the coals seemed uneffected until they were actually covered with water.
But you got me thinking.
The coal stove ashe gates seem to complex for me to build but what  about a rotating grate?
I couldn't find one , but this airlock diagram shows the basic idea.

rotary-airlock-expert-diagram2.png
Could be cast out of refractory.
Could be cast out of refractory.
 
John Suavecito
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William,
I liked the atmoko video. It's closer than others I've seen to something that could work for me.  I'm still rather feverishly trying to make biochar at a faster rate than that for my garden though.  It's not making enough, but it's still in the right direction.
John S
PDX OR
 
Douglas Alpenstock
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Justin, I had a look at your document. (It's also posted on the CleanBC website.)


Random thoughts:

- It's mighty ambitious. But there is a vast ocean between aspirational road maps and policies that can actually be implemented.

- Overall, the big push is for heat pumps and more heat pumps, and the replacement of fossil fuels in building heating.

- There is provision for natural gas / propane heat pump combination units.

- I think engineers would find some of their "100% efficient" statements quite hilarious. Real knee slappers.

- I saw a passing mention of renewables, which I expect includes wood.

- Lastly: I know people on Vancouver Island and the Gulf Islands. They vote for and elect Greens, federally and provincially. And you will have to pry their wood stoves out of their cold, dead hands.
 
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Justin,

A few years ago I made a very miniature version of the type of system that Mike was describing above.  Mine was made from old cans in the recycling bin plus a 1 gallon paint can.  The total parts list was:

1 paint can
1 bean can
2 soup cans

The bean can was filled tightly with tiny splits of oak and turned upside down in the paint can.  Tiny wood splits were then packed around the space between the bean and paint cans.  The paint can was filled almost to the top with wood, the rest was filled with wood shavings.  The paint can lid was punctured in the middle and cut at 90 degrees, enough so that the petals peeled back could firmly but not tightly hold a soup can with both ends cut off.  The second soup can set on the first with both ends cut off.  

Holes need to be drilled in the bottom of the paint can and in the soup can chimney.  Light the kindling and then tap down the paint can lid, attach the chimney and sit back for 90 minutes.  In the end, I got one can of char.

That’s a trivial amount but it is a practical proof-of-concept for a larger one if you want.

Eric
 
David Baillie
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Justin Hadden wrote:

John C Daley wrote:
I think your original statement may be incorrect, but I have seen similar laws around the world for cleaner burning units.




https://www.google.com/url?sa=t&source=web&rct=j&url=https://www2.gov.bc.ca/assets/gov/environment/climate-change/action/cleanbc/cleanbc_roadmap_2030.pdf&ved=2ahUKEwiV25qCq4P7AhVAFTQIHQUWBTwQjBB6BAgPEAM&usg=AOvVaw1pAC33eQRGDnVMa9bBS6_O

Its a long read, but if you skip down to page 40 and start reading there, it says "after 2030, all space and water heating appliances sold and installed in BC will be 100% efficient."

So you have to read between the lines, no combustions technology, whether wood, pellet, or gas can ever acheive 100% efficiency. The only truly 100% efficient systems are electric. Electric resistance heat converts 100% of its input energy into heat. Its a terribly difficult way to heat a space, but on paper i guess to them it looks good. The other funny thing is if you were to trace back all the way to the power plant (which is combustion technogy) then its probably even a less efficient process to heat my home electrically then it would be to simply have a wood stove in my home.

If you contjnue reading i believe on page 42 it talks about giving labels to everyones homes and giving it a carbon footprint rating for sales purposes. Meaning if some career political wannabe in a suit decides he doesnt like the way my household heats or cools or whatever they can give me a rating that will seriously affect my sales price.

Unfortunately with these things the government will hide the agenda deep in the text, i suspect as a way to avoid pushback. That seems to me to be exactly whatthe government of British Columbia are doing. Bury it in a massive document, and then most people will be taken by surprise by the time it comes to pass.


HI Justin,
the move as I understand it even in BC is towards "primary" heat. I highlighted the paragraph just before the one about 100 percent efficiency...

Space and water heating are the primary drivers of GHG emissions from buildings. To meet our targets,
we need to ensure these functions are super-efficient, improve resilience and, wherever possible, run
on clean electricity or other renewable fuels.


Wood according to that definition is "other renewable fuel" . I admit wood rarely gets talked about in urban drawn up planning documents.
Anyways, dangerously close to the cider press...
Cheers, David
 
William Bronson
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Is there anyone here that has built or used the "K" rocket stoves?
I'm curious as to how the combustion air is admitted.
"L" rockets often use a fuel shelf that delivers air to right below the the riser, do "K "rockets do that?

I am imagining a "y" rocket stove with fuel and air entering from the right arm, the right arm as the riser the tail  filled with water.
Seem like it should work, I'm just concerned about emptying the tail.
If the "tail" is big enough, it could be the base of the stove, and not need much emptying.

I have an old grill I lined with rockwool and a refractory hotface.
I intended it to be fired  from below by a tlud , but I think this theoretical "y" rocket stove might be a good fit.
The tlud needs more refined fuel, which is a either a pain in the butt or the wallet.
 
John Suavecito
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I want enough people to post on this topic that I will eventually actually understand what you are discussing. Keep 'em coming. I get a little hipper with each one.

John S
PDX OR
 
William Bronson
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There is a "traditional " woodstove design that seems like an ideal model for using with top lit up draft (tlud)stoves.
That design is the indoor sawdust stove.
Basic sawdust stoves are essentially Iike a log rocket stoves, but formed from sawdust.
They are natural draft rocket stoves that consume their own structure as they burn.

Indoor sawdust stoves are simply containers for the normal smaller stoves.
They are often made of steel barrels, and the flue even exits from down on the side of the stove, allowing the barrel to work like the bell of a rocket stove.


Sawdust stoves burn from the middle out, and tluds burn from the top down, but beyond that, they have very similar forms.

If we build start with an indoor sawdust stove made from a barrel, we could probably use it with either a sawdust stove or a tlud inside.

Pellets can be wetted to make sawdust.
I want to build a sawdust stove from a #10 can, so I can see how it burns.
Some of the videos seem to show the sawdust turning to charcoal.
A sawdust stove can burn many hours, so getting one to produce charcoal would be even better than using a tlud.

 
William Bronson
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It looks like the combustion process in a sawdust stove is indeed a lot a like what happens in a tlud.
This not too surprising, there are a few charcoal producing rocket stove designs that use sawdust or wood chips as insulation that is gasified into charcoal as the the stove runs.
The Hookway Retort is a large example, the Anila stove a small one.


I propose using a pellet smoker tube as the center pipe that sawdust is packed around.
By doing this we can leave it place and prevent
the airway of the stove from collapsing as the sawdust pyrolysises.

KSG-stove5.jpg
Pyrolysis in a sawdust stove,from the center outwards.
Pyrolysis in a sawdust stove,from the center outwards.
Anila-stove-combustion-cycle-Freese-Green-2008.png
Anila stove.
Anila stove.
51RdePVv5uL._AC_SY1000_.jpg
Pellet burning smokertube. all thsr
Pellet burning smokertube. all thsr
 
William Bronson
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I have been working nights, so 'I've had lots of time to think (obsess) about this topic, and no time to actually experiment, so please for give my untested theorizing.

It needs to be said, none of these stove ideas are as clean burning as a proper rocket stove.
They also have no provisions for storing heat in a thermal mass.
If they are not gonna burn as clean and efficient as a proper rocket stove, they should be simpler to build and or operate, and they should make charcoal.
Connecting them to thermal mass should be a primary goal, but it can come later.


I was thinking about the air flow in a sawdust stove.
They burn a longing time, but relatively hot and clean.
Usually one must give up some part of this trio.
With a very minimal exposure of the fuel to the air, we might expect dirty  smoldering burn.
I think the geometry of the sawdust stove forces all the combustion gasses to pass through the flames in the center.
It is in effect a flame cap charcoal kiln, the "cap" just happens to be in a central cylinder region.

Examples of  flame cap charcoal kilns are any pits, cones, or trough kilns that work by a maintaining flames on top of the fuel.
The flames exclude oxygen from the fuel, preventing the coals from burning down to ash.
It's a great system, but it requires intervention in the form of  adding fuel.

The TLUD(Top Lit Up Draft) kiln provides air that passes upwards through the fuel , so its consumed once it meets the downward descending combustion zone.
Tluds are set and forget devices, you have some time before you need to check on them.
But they do require fuel that is relatively refined, at least in my experience.
I think if I am more careful in building my fires , this wont be an issue, but that requirement isn't helpful for widespread adoption.

Can we have a  device that burns unrefined fuel for along time without human intervention ?
Can we capture the heat and get the charcoal?
I started looking into top down fires for charcoal production.
I'm talking fires that don't have  Up Draft, no air introduced at the bottom.
Maybe  you can fill a barrel with fuel and light the top and it might burn down slowly, and pretty cleanly.

My internet searches are inconclusive , because no one seems to have the same goals I might, so I want to try this with a tin can  filled with wood pellets.
This would be a Top Lit and Top Draft charcoal kiln, if it works...

A separate but not unrelated idea is a consumable grate.
In a TLUD this would consist of  pieces of wood that are strong enough to hold the fuel in place.
When the combustion zone reached them and they burn down to a coal state, everything falls into the liquid filled receptacle below.

The tin can version will use twigs or bamboo skewers , with maybe a handful of straw or something, then wood pellets .
The same holes that admit air into the bottom of the can hold the twig grate, and I can set it on top of a second can filled with liquid.
This would be a Top Lit Up Draft Wet Douse  (? )charcoal kiln?

Back to top lit up draft fires in general.
The "new " trend in wood stove fires is a top lit fire.
Wood stoves generally deliver air at a low point in the firebox, and supplement with secondary air, etc.
So these top lit fires operate not unlike a Tlud kiln.
Intervening in these fires at the coal stage could yield a lot of charcoal.
I think some folks do this, but its the intervening part that sucks.
If a top lit fire can burn long and clean, without updraft, because of the flame cap, maybe we could do the same in a wood stove.
If a firebox full of fuel is lit from the top, with both air and exhaust path only available at the top of the firebox, we might be able pyrolyze the entire load over a long time, relatively cleanly.
When the combustion zone hits the bottom of the fuel, maybe it consumes the grate than is holding it suspended in the stove and the entire coaled over fuel charge  drop into a pit of liquid.

The tin can version of this has holes for twigs or bamboo skewers to create consumable grate, but the holes are sealed with wax once the sticks are in place.
Paper goes on top of that, and then a wood pellets.
Liquid goes in the bottom.
This would be a Top Lit Top Draft Wet Douse  kiln, I suppose.
I'm not in love with any of these names, but the devices aren't real yet , so...


If I can get the consumable grate idea to work, it will free up my attention.
Adding this feature  to my in progress TLUD wood boiler may not be possible or at least not easy.
I burned my trough kiln the other night, and it took to long, too much attention, and was too smoky.
For my own immediate use, a barrel sized TLUD that self extinguishes is plenty good.
If the tin can Top Lit Top Draft Wet Douse  kiln works , I'll build a barrel sized one as well.

Or maybe Ill get distracted and never proceed, but I hope not!





 
Michael Cox
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I collected some takeaway pizza yesterday from a little italian place near my work. They use a woodfired oven.

The chef walked through the restaurant carrying a metal pail full of embers. I suspect that they needed to do this multiple times per day. If they quenched these embers each day then they would quickly build up a decent stock pile. Super simple. They just need to dump it in a bucket of water.




 
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i am new who do i contact for assistance in growing food and making this stove
 
Eino Kenttä
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William Bronson wrote:
The coal stove ashe gates seem to complex for me to build but what  about a rotating grate?
I couldn't find one , but this airlock diagram shows the basic idea.


Somehow I only saw this now. That looks really cool! Would it be self-rotating (the char falls down on one side only) or would you manually turn it? And do you figure it would be best to let it empty straight into water, or into a mostly airtight holding container?

I had started thinking more simplistic, like the char falls through the grating and ends up on a metal plate that can be pulled out towards the front, so the grate bars push the char off the plate and down into the char box. The plate then acts as a lid for the char box. But, well, your idea is way cooler...
 
Eino Kenttä
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Hi Camelia, welcome to Permies!

These forums are full of knowledgeable people in many different fields. Just keep reading, and ask questions if you wonder anything in particular. You'll learn most of what you need to get started.
 
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Camelia Jones wrote:i am new who do i contact for assistance in growing food and making this stove



Camelia, Welcome to the forum!

For growing food:  https://permies.com/c/growies

This forum might be a good place to start:

https://permies.com/f/124/gardening-beginners

To make the stove this post has a good explanation:

Eric said, "A few years ago I made a very miniature version of the type of system that Mike was describing above.  Mine was made from old cans in the recycling bin plus a 1 gallon paint can.  The total parts list was:

1 paint can
1 bean can
2 soup cans



See the rest of the post for details:

https://permies.com/t/197517/Biochar-producing-wood-stove#1688742
 
William Bronson
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Eino Kenttä wrote:
I had started thinking more simplistic, like the char falls through the grating and ends up on a metal plate that can be pulled out towards the front, so the grate bars push the char off the plate and down into the char box. The plate then acts as a lid for the char box. But, well, your idea is way cooler...



I like your idea!
It's simple and straightforward!
 
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