Using biochar heat for other uses

Just curious. Has anyone thought about how to use the heat from making the biochar for something else? Any heat differential is possibly a source of electricity.

Kathryn Skinner wrote:Just curious. Has anyone thought about how to use the heat from making the biochar for something else? Any heat differential is possibly a source of electricity.

I've googled it, and I think it'd be technically possible...but you'd be talking about like enough power to change a cell phone, or maybe run a string of LED lights...not much more. So, if that was a scenario that'd be useful, it'd be worth exploring.

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.

Using the heat as either heat or for drying makes a lot more sense than converting it to electricity from an efficacy standpoint. Drying lumber (while making biochar of the scraps?) or maybe drying inputs for your next char? I like it!

My 55 gallon barrel has a shelf on it, around the chimney.  It's really hot, as you can imagine.   I use the shelf as a place to put wood just before it goes into the barrel. It dries out the wood nearly perfectly before it goes in, and that makes the burn more efficient.  Sometimes it gets char marks on it or even occasionally starts burning.  That's how I use the heat that would be lost.

JohN S
PDX OR

This is one of my favorite subjects.
Space heating is the obvious best use, followed by fuel drying.

I have built a Tlud powered boiler for heating a greenhouse while making charcoal at the same time.
It sits, decommissioned, waiting for me to take another stab at it.

I think it was Sean from the Edible Acres YouTube channel that popularized using stainless steel steam table pans as a retort in a wood stove.
Small fuel that would other wise burn very quickly, is slowly converted to charcoal and contributes to warming the house.

When I consider rebuilding the Tlud boiler, it's with adding a retort in mind.
I would keep the option to fire it with a Tlud, but I like the idea of using a small charcoal fire to start the pyrolysis.
Tluds work best with regularly shaped "refined" fuel like pellets or rice hulls, and they need to be dry.
Sifting charcoal to get regular sized pieces is easier than chipping then sifting wood, or cutting wood to size.

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.

William,
These are great ideas for using the heat.
JohN S
PDX OR

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 think Eric built a 12"er here: https://permies.com/t/174665/Huge-batch-box-rocket-stove

Kathryn Skinner wrote:Just curious. Has anyone thought about how to use the heat from making the biochar for something else? Any heat differential is possibly a source of electricity.

Yes, the heat from biochar production can potentially be captured and reused. Many systems already use the heat or syngas produced during pyrolysis for tasks like drying biomass, heating buildings, or running the process itself.

Using the heat difference to generate electricity is possible through technologies such as thermoelectric generators or small heat engines, but the efficiency is usually limited unless there is a large, steady heat source. For small-scale biochar setups, using the heat directly is often more practical and efficient.

I have always been very impressed with https://newenglandbiochar.com/.

They use syngas to create electricity and low grade waste heat to heat kilns and greenhouses.

I’ve seen a few hobbyists run antique wood fired steam engines for small scale sawmilling.  An auger setup connected to the fire box could remove coals for quenching while the engine ran the sawmill, generator, etc.  No doubt it would work, but probably beyond what the average homesteader would be willing to do.    Don’t think small steam engines are particularly efficient either.

Jeff Marchand wrote:I have always been very impressed with https://newenglandbiochar.com/.

They use syngas to create electricity and low grade waste heat to heat kilns and greenhouses.

I have had fantasies about starting a business that creates biochar using New England Biochar tech and use waste heat for black soldier fly processing of food waste into high protein animal feed and as energy source for ethanol production ala David Blume's Alcohol Can be a Gas .

As always its lack on money and debt aversion is standing in my way.  A person can dream though can't they?

Kathryn Skinner wrote:Just curious. Has anyone thought about how to use the heat from making the biochar for something else? Any heat differential is possibly a source of electricity.

That’s actually a really interesting idea. The heat generated during biochar production is often considered a byproduct, but there’s definitely potential to capture and use it. Some systems already use the heat for things like drying biomass, heating buildings, or generating steam. In theory, with the right setup, temperature differences could also be used for power generation through technologies like thermoelectric generators or small-scale turbines. The challenge is making it efficient and cost-effective enough to justify the extra equipment. It seems like there’s still a lot of room for innovation in making biochar production more energy-efficient and integrated.

Kathryn Skinner wrote:Just curious. Has anyone thought about how to use the heat from making the biochar for something else? Any heat differential is possibly a source of electricity.

Yes. The easiest use is capturing the heat for cooking or heating water instead of letting it go to waste. Generating electricity with thermoelectric generators is possible, but they're not very efficient and usually only produce enough power for small electronics. For most setups, using the heat directly makes the most sense.

Using the left over heat to dry wood is an interesting idea, but i believe it will be much too difficult to manage if he is making any type of dimensional lumber. Kilns have precise temperature control needs and schedules. Depending on thickness of wood, you could be talking 5 days or up to 8 weeks. Dry the wood too fast and it cups, warps, and splits. Too quickly and mold and fungi become your main issues. Air drying skips most of that worry. If you decide to give it a try, let us know how the project turns out!

I have made some very good, glassy low soot biochar in my home woodstove inside a dutch oven, with the heat warming my house and boiling water or making soup. I used end pieces from firewood cuts that fit into dutch oven. It was a very low volume (2gal) to work ratio though, and had inherent risks of burning myself moving the red hot dutch oven out of the stove. Compared to the B+ biochar I can make with the 6ft diameter Ring of Fire with green brush, by the hundreds of gallons per batch while doing wildfire prep shaded fuel breaks, doing it the former way seems unwarranted to me now. If you manage your wood stove carefully and forego the heat of the charcoal left after volatile gasses burn off, it can produce decent char on its own too.

R. Ford wrote:Using the left over heat to dry wood is an interesting idea, but i believe it will be much too difficult to manage if he is making any type of dimensional lumber. Kilns have precise temperature control needs and schedules. Depending on thickness of wood, you could be talking 5 days or up to 8 weeks. Dry the wood too fast and it cups, warps, and splits. Too quickly and mold and fungi become your main issues. Air drying skips most of that worry. If you decide to give it a try, let us know how the project turns out!

I made a post in this same thread 3 days ago to answer this question. I have been doing this for years. It greatly improves the quality of the burn: less smoke, less water vapor, faster, cleaner burn. I air dry it somewhat before hand, but sometimes I split the wood that day and finish drying it on the shelf of the barrel. It works great.

" posted 3 days ago

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My 55 gallon barrel has a shelf on it, around the chimney.  It's really hot, as you can imagine.   I use the shelf as a place to put wood just before it goes into the barrel. It dries out the wood nearly perfectly before it goes in, and that makes the burn more efficiently.  Sometimes it gets char marks on it or even occasionally starts burning.  That's how I use the heat that would be lost.

JohN S
PDX OR