Making biochar from miscanthus or SRC willow?

[Sonnyjim]

Dear all,

This is my first post on the Terra Preta boards. I'm a recently-started PhD student at the University of Lancaster, UK, and I'll be working on a biochar field project for the next few years.

 

I have a question that I was hoping someone could help me with. A couple of the feedstocks that we are considering to use a biochar include miscanthus and short rotation coppice willow. Now I believe that this has been done using small-scale stoves. But what we would like to do is create biochar from this thin (i.e. less than 2cm diameter) feedstock on a larger scale (to produce field trial scale quantities e.g. in the hundreds of kilograms).

 

A charcoal producer that we have been in contact with said that using thin feedstocks such as miscanthus or SRC willow is not suitable using a retort kiln because 'everything will turn to dust', because of their small diameter. Can anyone with experience of making charcoal/biochar confirm that this is true? If so, does anyone have any suggestions for what technique could be used to create a large amount of char from a thin feedstock such as these?

 

Thank you all in advance for your help,

 

Sean

[Essay]

A charcoal producer that we have been in contact with said that using thin feedstocks such as miscanthus or SRC willow is not suitable using a retort kiln because 'everything will turn to dust', because of their small diameter. Can anyone with experience of making charcoal/biochar confirm that this is true? ...Sean

Welcome SonnyJ; ...hope we can help....

 

I think this is an important factor; a question with complex answers.

 

There are ways of making biochar out of small diameter material, but the density of the char can vary depending on production conditions for a given feedstock. For low density chars, I would think that any large scale handling of the product -either during production (as in a retort perhaps?) or during collection, packaging/handling, and distribution- would lead to a lot of breakage and dust production.

 

I've seen biochar that was as hard as an antler (from wood buried in superhot sand, I think), but you don't want that much density, so there must be some process that will give you the desired structural properties to balance the ease of handling of biochar with the efficacy of biochar as a soil amendment.

===

 

 

I might find some more information next week, but...

I would guess that longer pyrolysis treatment times, and low to moderate temperatures (with maybe a few brief high temperature excursions) would allow for the most secondary biochar to form (which should be more dense since it grows like a crystal, instead of forming from the remains of decomposed larger organic molecules, imho).

 

p.s. Are you cogenerating bio-oils from these nice woods as you make biochar?

[donnie char]

Sean, I applaud you for choosing this field of study, you put you finger on the question that I'm working on. how does one carbonize any type of biomass with out regard to size, species or moisture content. I'm working with steam pyrolysis . At first generating 500C steam with a burn barrel boiler , then working out the rotating drum retort for continuous feed. finally switching to solar power for the heat source. And as to char particle size. I have found in our test plot that fine root hairs readily attach to sand grain size char (1-2mm) .All the field tests done in the states by the department of agriculture have been with Dynamotive"s char which is very fine dust. and if you keep it wet when handling the level of raised dust is checked.

[Sonnyjim]

Thank you for your replies Essay, and Donnie Char. I found them both very useful.

 

Since my original post I have tried to get in contact with some researchers who have made biochar using miscanthus, however just on a small-scale using muffle furnaces or the like. The production process is a lot more intricate than I initially assumed, and I can imagine spending a whole research project just on optimising the production process and end characteristics of thin-diameter char such as miscanthus and SRC willow, let alone getting a field-scale study!

 

Thank you for your advice on the production technique Essay. Soon we will have a muffle furnace ready and equipped with an N2 gas inlet so I will be experimenting with the long residence times and low to moderate temperatures (I guess between 350 and 450-500C?) that you mention to see if I can get any decent miscanthus char out of it. As for collecting bio-oils, I'm not sure if that will be possible with the equipment that we have, as all of the gases and volatiles seem to disappear up and out of the furnace, through the filter above and then outside. But I can get back to you on that in the future to see if we have a way to do that here.

 

And Donnie Char, thank you for your words about the production process you use, and the possibility of using 'dust' char, even though it is 'dust'. It is true that we also could apply 'dust' char (1-2mm) to the field, but what I am concerned about is our facilities in terms of transport (4x4s), storage (in bags/boxes in laboratories basically) and field application techniques (throwing the char onto the field basically, we don't have the equipment to incorporate into the soil save by manual means e.g. spades/forks).

 

Without the equipment that comes with a specialist biochar producing company such as Dynamotive, and proper farm equipment in order to broadcast/incorporate the char into the site, I worry that the task of handling this 'dust' char will be a very difficult problem.

 

Thanks again for your help!

 

Sean

[AmanM]

Hi,

 

I am working too on making Biochar from forest litter. I will be using a muffle furnace for the experiment. Liquids cannot be collected from the furnace but it is possible to analyse the gas through its outlet. As far as I know muffle furnace is not idle to produce large quantities of Biochar. You will be using a lot of electricity and also the furnace does not have a large capacity. You could try making a stove(designs are available here :Biochar Production Methods)

but the only problem would be maintaining the temperature, which you could handle by the amount of fuel )

 

-Aman

[erich]

There are some folks Pelleting and then you can run a simple TLUD for space heat,

on this thread;

http://hypography.com/forums/terra-preta/15195-biochar-manufacturers-4.html#post291259

 

Chip Energy Biomass Furnace

500 lb chips / day = 180,000 BTU / hr + 85lb Biochar / day

The price of chips and / or pellets would be more than off set by bagged char sales of $50 / day

500lb wood pellets cost = $40

500lb Hogfuel / wood chips = $10

In other words; Free Heat

Home

 

This to the Biochar list from Dr. Paul Anderson;

 

 

 

Dear Kelpie and all,

 

You seek a heat generation device at household or institutional sizes

that leaves the charcoal after pyrolysis in completed. You specify

pellets, but decent wood chips would also be a desirable fuel.

 

Such a device already exists, and is available to be incorporated into

projects that further its development and applications. (It is not

yet for public sale as a commercial product because the necessary

corporate structures and permits require further R&D and investments).

 

The device is the Chip Energy Biomass Furnace. See the basic info at:

Home

The unit shown is currently used daily for supplemental heating of

Paul Wever Construction Equipment, Inc (16,000 square feet industrial

space) in central Illinois. It produces approximately 180,000 Btu per

hour, is fully automated, and in a 24-hour period uses about 500

pounds of pellet fuel and produces about 85 pounds of biochar (17%

yield by weight of raw fuel). It can be adjusted to remove the char

faster, which would increase the biochar yield but reduce the

heat-per-pound delivered to the heat exchanger. The biochar is being

sold for 25 cents per pound to research institutions. All analytical

reports about the biochar properties have been highly favorable.

 

That furnace was developed with assistance from a US EPA SBIR grant of

$70,000 as a prospective replacement for the outdoor wood boilers. We

have documentation on the EPA project and the highly successful

outcome, including very favorable emissions tests. It can operate

unattended as long as there is a fuel supply and the biochar collector

is periodically emptied; control is by a PLC and an array of sensors

plus safety systems.

 

The unit is based on updraft gasification, as explained in the

published document--- "Micro-Gasification: What it is and why it

works." (Anderson, Reed and Wever, 2007):

http://www.hedon.info/docs/BP53-Anderson-14.pdf

 

It is scalable smaller (see the Chip Energy Biomass Grill at the same

website), and can be made larger with multiple gasifiers (but one

control system and fuel hopper) to approach one million Btu per hour,

and can be scaled larger as single units (a topic of current R&D).

 

The Chip Energy Biomass Furnace as currently configured sends its heat

to a flash boiler (avoiding the high pressure issues of steam

boilers). Entities that desire the heat to go to steam boilers simply

need to participate with that expertise in a project with Chip Energy.

Chip Energy welcomes any possible projects into which the Biomass

Furnace could be incorporated.

 

Discussion of the issues raised by Kelpie can be on this Listserv.

But business inquiries should be addressed off-list to Paul Wever at:

[email protected] or phone him at 309-965-2005 begin_of_the_skype_highlighting 309-965-2005 end_of_the_skype_highlighting

 

Paul

--Paul S Anderson, Ph.D. -- aka Dr. TLUD ("Dr. Tee-lud")

Biomass Energy Consultant with BEF, & Partner in Chip Energy.

Specialist in micro-gasification. Office & Res: 309-452-7072 begin_of_the_skype_highlighting 309-452-7072 end_of_the_skype_highlighting

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