What Shouldn't We Make Biochar Out Of?

Ebo David wrote:
re: temperatures...
Agreed, but I also see listed places that some retorts work as low as 300C, hence my comment about removing any which has not been completely charred.  It would be interesting to look at how well it broke the organic compounds, but as someone mentioned (you?), placing that at the drip-line of the same species of tree would likely help it...

I don't consider charcoal produced at low temperatures to be biochar, per se. If you don't get it hot enough to convert all the hydrocarbons to aromatic ring structures and develop porosity, it's not going to do the things in soil that we're looking for. Setups that fail to reach treatment temperatures of at least 400-450C are insufficient and in my view aren't really biochar retorts. The end product will add carbon to your soil and eventually most of it will get devoured by microbial activity, so it's not a bad thing so much as a missed opportunity.

If you make a batch of biochar and spot some pieces that didn't cook all the way through, they can just go into the next burn.

Yes, there are a whole list of plants that extract toxic metals. Rice hyperconcentrates arsenic, so you could use it for that purpose, but you have to be careful when you buy rice. Until very recently, it was legal to feed arsenic to chickens that were sold as meat to people. This was very common in the American South.   There are even mushrooms that tend to do that, although I don't know if they are easy to cultivate.
John S
PDX OR

Jay Angler wrote: Special and important situation for you Ebo. I read a book about soil repair in Britain. Sunflowers were specifically grown for their ability to clean the soil of lead. You could grow and then dispose of to the dump, to get any lead off your land. In heavily contaminated sites, they actually dried the sunflowers and sent them to a company that burned them and recaptured the lead. Sometimes the problem really is the solution - less lead mined if we recapture it.

Can you find me any references to the work where they recaptured the lead from the sunflowers?  I would be very interested in this.

Anyway, the mutation I have is in about 3% of the population.  A different mutation is prevalent in ~30% of the population.  So it is a lot more common than people realize.  The 30% mutation does not effect the overall biochemistry over much, but the mutation I have causes me to hyper accumulate just about all metals before I started taking mentholated forms of my vitamins.  It does not help that I grew up in a family of potters, and we routinely went through a 55 gal drum of red lead paint each year.  At this point I am still leaching it out of my bones...

Jay Angler wrote: There are other plants with strong affinity to other elements/chemicals to the point that there is now talk of using them to "mine" those chemicals in suitable areas. My concern with the article I read on that subject is the tendency for humans to plant monocultures and then wonder what went wrong when Mother Nature gets annoyed.

There is a WHOLE other discussion.  I can see using monocultures of plants like sunflowers for a time (assuming they plan to eventually replace them with a divers mix, and natives preferably).

John Suavecito wrote:Yes, there are a whole list of plants that extract toxic metals.

Yes.  There is an entire scientific discipline focuses on that - Pytoremediation:
 
 https://www.epa.gov/sites/default/files/2015-04/documents/a_citizens_guide_to_phytoremediation.pdf

Off the top of my head, there are 3 things you should not turn into biochar:
01 Table sugar/sweets. They turn into pure carbon without any structure and they expand to choke off air flow either within the retort or outside it. Nasty.
02 ANTHING from the https://en.wikipedia.org/wiki/Manchineel . Toxic fumes when burnt.
03 Check with your extension service about any other woods that give off toxic fumes when burnt.
I throw in lead weights like those used for balancing tyres. That melts at 327C. I also throw in used tealights. Sometimes the aluminum melts when in contact with the red hot embers. That melts at 660C.  

Ebo David wrote:Can you find me any references to the work where they recaptured the lead from the sunflowers?  I would be very interested in this.

It was a library book from Britain where they refer to these sites as "Brownfield". Not sure my library would even still have it, but I'm not in my home province at this time. My recollection was that it was a highly contaminated site, thus they were able to concentrate certain chemicals into plant matter sufficiently to be worth a company extracting it.
https://en.wikipedia.org/wiki/Brownfield_land gives some of the lingo, but I'm not in a position to hunt further at the moment.

The reference to plants mining - yes -

There is a WHOLE other discussion.  I can see using monocultures of plants like sunflowers for a time (assuming they plan to eventually replace them with a divers mix, and natives preferably).

Short term monocultures may have their place, but I always worry that they're a pest magnet and if money gets involved, humans tend to use negative measures to control "pests" rather than working with nature to find safer solutions. A monoculture of sunflowers for even several years in an effort to clean up lead contamination would be understandable, but surrounding that field with a polyculture border to support predator insects, might be enough to support the sunflowers. I was at a talk about bees and a case study was about planting around the edges of industrial strawberry fields and they were actually able to show how far into the field the insects went - in other words, optimum field size for pesticide free strawberry growth. There is so much nifty research people could do, by thinking outside the box and observing nature.

Jay Angler wrote: It was a library book from Britain where they refer to these sites as "Brownfield". Not sure my library would even still have it, but I'm not in my home province at this time. My recollection was that it was a highly contaminated site, thus they were able to concentrate certain chemicals into plant matter sufficiently to be worth a company extracting it.
https://en.wikipedia.org/wiki/Brownfield_land gives some of the lingo, but I'm not in a position to hunt further at the moment.

I am not in a hurry, and if you are willing to put this on a "when I get around to it list", I really would like as much details that you can get me.  I'll poke around online and see if I can dig things up as well.  Part of my background is in restoration ecology (both in the UK on projects in the Norfolk Broads, the Peterborough Fens, and a little work in the New Forest), as well as wetlands/uplands all over the US, and dry-land forests of the Rocky Mountain west.

My current interest in phytoremediation/bioremediation is to consider using that as a technique next to my wife's house -- which is heavily contaminated with lead over the last 100 years.  I have other research interests that are more directly related to the mining, but that will be a full on research paper, and I am not even close to discussing that as a project publicly, but you gave me a place to look for interesting literature ;-)

Short term monocultures may have their place, but I always worry that they're a pest magnet and if money gets involved, humans tend to use negative measures to control "pests" rather than working with nature to find safer solutions. A monoculture of sunflowers for even several years in an effort to clean up lead contamination would be understandable, but surrounding that field with a polyculture border to support predator insects, might be enough to support the sunflowers. I was at a talk about bees and a case study was about planting around the edges of industrial strawberry fields and they were actually able to show how far into the field the insects went - in other words, optimum field size for pesticide free strawberry growth. There is so much nifty research people could do, by thinking outside the box and observing nature.

Nice spatial planning on the boarders.  Decades ago I worked for a landscape ecology academic researching similar.  If you have large fields, you can plan islands of refugia for pollinators and predators dotted across the mono-culture fields, and as long as they are within the flight dispersal distance of the species of interest, you are golden.  I would also not place the islands at the max distance, but more like 80%, so that the species flow is sufficient to keep them well stocked.  As a note, you can do this in the opposite -- and separate plantings by significantly more than that distance to discourage propagation or diseases, pests, disturbances (like fire).

The one place where I used the mono-culture thing to good effect was post dam removal on a 100 to 150 year old dam at about 3,000m elevation.  We selected plants that would not take the over wintering well to stabilize the soil.  Since they were required to monitor the site for several years, as part of the mitigation process, one of the tasks was set up specifically to make sure that it did not produce viable seed.  So the first year after seeding we had good ground cover, but it all died in the first heavy frost before producing viable seed.  Second season there were a small handful of seeds that germinated from the first round, but also died before producing viable seed.  By the second or third season it was all gone, the soil was stabilized, and the natives were filling the space in.  Anyway, that is how I remember that part of the project, but that was something like 30 years ago...

I have been warned to avoid wild cherry wood. The smoke is toxic and can potentially contaminate the soil.

That's an interesting statement. There are wild cherry trees all over the forests here, and I've never seen or heard that kind of impact.  80% of the sweet cherry crop in the US grows here in the PNW.  If you have a cherry tree, you will find its children nearby.

John S
PDX OR