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pH question: charcoal as soil amendment

Posted by fabaceae_native (My Page) on
Mon, Dec 17, 12 at 15:18

There appears to be some confusion about the effect of charcoal on the pH of the soil. Charcoal is generally alkaline to varying degrees, but a found some sources claiming that it can be used to LOWER the pH of the water used in Hydroponics!

The pH issue might not be a concern either way though, since very little charcoal in the soil still has a beneficial effect. One scholarly article I read claimed that just 1% charcoal by weight in the soil is enough to reap the benefits.

So here's my question: would adding charcoal to a soil at the rate of 1% really make it any more alkaline, even if the charcoal had a pH of 8 or 9?

I've already given up trying to use the ashes from my woodstove because of their caustic nature, but I started to sift out the softwood charcoal and am dying to use it in my homemade potting soil and in the garden. Visions of Amazonian Terra Prieta are float around my mind... :)

Thanks for any feedback.


Follow-Up Postings:

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RE: pH question: charcoal as soil amendment

What exactly has made you not want to use the fly ash?

My understanding is that char does not raise or lower ph significantly.


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RE: pH question: charcoal as soil amendment

  • Posted by ericwi Dane County WI (My Page) on
    Mon, Dec 17, 12 at 22:46

Charcoal is not water soluble and should not have any immediate effect on pH. It would have to be metabolized by bacteria or fungi and then it is likely be incorporated into organic acids that would eventually lower pH slightly. If there is adequate moisture, and excess sulfur present, then you would see soil pH drop significantly, in a year or two.


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RE: pH question: charcoal as soil amendment

Generating charcoal and bio char means large amounts of pollution are released to the atmosphere even though both may, once made and having released large amounts of pollution, aid in sequestering some CO2 in the soil.
Before using wood ash in the garden a good reliable soil test should be done to see if the large amount of Calcium Carbonate from that ash is needed.


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RE: pH question: charcoal as soil amendment

kimmsr: I won't be adding any pollution, since I'll be using the charcoal I am sifting out of the ashes from my woodstove. In other words, it is being produced anyway, and I am just trying to find a good use for it.

But you stated exactly why I am reluctant to use the ashes themselves, to answer pnbrown's question -- namely a soil pH that tends to be on the high side already.

Thanks all for the info, I think I will go ahead with putting this stuff to good use.


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RE: pH question: charcoal as soil amendment

"In other words, it is being produced anyway, and I am just trying to find a good use for it."

I agree completely. It seems easy to understand, but you will find that some here cannot or will not, no matter how many times it gets discussed.


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RE: pH question: charcoal as soil amendment

To answer your original question, no, I don't think 1% at a pH of 8-9 will have any measurable effect

Charcoal sifted out of the ash will have some ash clinging to it, of course, so I wonder if this is what people are talking about? But fish tank charcoal will likely be very well washed and shouldn't have soluble bases still in it. So perhaps the carbon matrix does indeed have some basic properties. News to me.

I've sifted ash myself and spread the fine charcoal on the garden. I've read (from reliable sources) on this forum that the alkalinity in ash is leached out over the winter, at least in their situations, and seems to have no detrimental effect. So although I haven't put large amounts of ash down yet, I'm no longer as concerned about what's clinging to the charcoal.


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RE: pH question: charcoal as soil amendment

someone who understands chemistry better than I do should answer this one.

charcoal acts as a binding agent, which makes it effective as a filter for any number of purposes. since pH is actually a measure of the concentration of hydrogen (in this case, in soil), if charcoal binds with various compounds in soil solution, replacing hydrogen, freeing hydrogen in the soil, the pH is lowered.


never heard a report of charcoal pH. never tested it either.


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RE: pH question: charcoal as soil amendment

Charcoal is a binding agent, but theoretically, it's a completely covalent type of matrix, and does not have ion exchange sites like clay minerals (for example). Which is why it will take up organic compounds like pesticides, petroleum hydrocarbons, etc. so well.

I'm sure it's not perfect, for example there could be some partially oxidized surfaces, so there might be some carboxylates hanging off (i.e. organic acid groups). That would make it slightly acidic though, not basic.

All this is theoretical...although (coincidentally) I did quite a bit of research on activated carbon in my chemistry graduate research, it is a very involved science and there is much that I don't know.

Bottom line, I would not expect it to measurably affect the pH of soil.


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RE: pH question: charcoal as soil amendment

A cubic foot of soil weighs from 75 to 100 pounds...how dry? I don't know. 1% would be 3/4 to 1 pound per cu. ft..


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RE: pH question: charcoal as soil amendment

The charcoal used in filters, and as a poison antidote, is activated charcoal which is different then the charcoal produced in a wood burning stove of brush pile, both of which produce the same amount of pollution although you do get some useful heat from the stove.
No matter how it is produced making charcoal produces large amounts of pollutants and wastes valuable nutrients.

Here is a link that might be useful: About Activated Charcoal


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RE: pH question: charcoal as soil amendment

" although you do get some useful heat from the stove."

I realize you mean that as unimportant, but in fact it's the crux of the argument. For people in northern climes who are heating their houses with wood, the charcoal produced, over some years, is a very large and important addition to a home garden, easily leading to sustainability and independence from outside inputs.

Activated charcoal is simply charcoal that has been exposed to sufficient temperature without oxygen to drive off everything except C. Charcoal of such purity no doubt has the highest ability to sequester minerals and moisture and thusly microbes. But any charcoal is quite useful, and it all should go to the garden, and not everyone knows that.


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RE: pH question: charcoal as soil amendment

Well said. I am not particularly in favor of burning stuff just to make charcoal for the soil, and I never do that. When it's a byproduct of something I'm doing for another purpose, I use it.

Actually I had to burn some brush piles this year, and I sifted out 3 sizes of charcoal: big, for the bbq grill, small, to go back into the woodstove, and <1/4", which went into the soil. Nothing's wasted!


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RE: pH question: charcoal as soil amendment

I have a large area of pasture in central fla, and many different efforts to raise SOM have been of little effect. This is due to hyperthermic sand and high evaporation rates creating conditions that do not favor the decay cycle necessary to convert C captured by plant growth to SOM. In this environment the C is constantly returning to the atmosphere from the withering of herbaceous plants during the dry season and from the very slow desiccation of dead wood.

I am looking at biochar now as a way to artificially create the missing decay cycle.


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RE: pH question: charcoal as soil amendment

I have been making and using biochar for the last 4 years with good results.
I make a large amount of softwood scrap waste and planer shavings, and the only way to get rid of it is to create biochar which needless to say then goes into my garden.
I use a two barrel set up and convert at least 70% of my waste into high quality charcoal, with little to no smoke.
There is no apparent change in .Ph, but I do notice the lack of watering needed. I believe the biochar holds a great deal of water which the plants take advantage of.


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RE: pH question: charcoal as soil amendment

Mr. Brown, your assumptions about what I mean are often very erronious. I well understand that in my area of the world many people use wood for heat, but they often do not realize the amount of pollution they contribute to the atmosphere.
You might wish to spend some time at the link I provided above to learn about activated charcoal.


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RE: pH question: charcoal as soil amendment

You might wish to spend some time studying types of implements for the combustion of wood, as well as consider what ways exist of producing artificial heat without creating pollution. It is possible to live in a small space heated by the metabolic activity of humans and animals. That's why people used to live with their livestock. Still they had to cook.

Anyway, since you now claim you understand that what we are talking about is the use of a by-product, why do you continue to dun the use of char as an amendment, based on the fact that air-pollution is caused in the making of it?


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RE: pH question: charcoal as soil amendment

Hey you two, Santa's watching! :-D

beeman: I use my planer shavings in compost. Some go into my own, and some go to the office as a brown to mix with our daily coffee grounds and food waste. It does compost given enough greens. But I'm a casual woodworker producing a few trash bags a year, so if you have a huge amount, I guess I can't blame you for making char out of it.

BTW my woodstove is catalytic, and although it creates more soot pollution than the natural gas furnace, it does pretty well and is not putting fossil CO2 into the air. For about a decade during the real estate boom, all my wood was from development sites that was going to be burned in a big heap anyway. I harvested the heat AND cut down on the pollution compared to uncontrolled burning.

It's all pros and cons and all situations are not equal.


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RE: pH question: charcoal as soil amendment

I for one am happy to own a passive solar home, which requires very little supplemental heat, and then only during cloudy weather (and yes, this really is zone 6, we get subzero temps nearly every winter). This is much more worthy of advocating than the fact that burning wood pollutes.

I see wood as a much better source of heat than anything run on fossil fuel. After all, wood is a renewable resource that can be obtained in a sustainable way (and we can use the waste products in the garden -- the original theme of this post).

Thanks all...


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RE: pH question: charcoal as soil amendment

Perhaps this from Canada Public Health might be of some interest.

Here is a link that might be useful: Pollutants from wood burning stoves


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RE: pH question: charcoal as soil amendment

Green Guilt everywhere. ;)

Burning wood does NOTHING to the environment. When a tree is growing it has a negative carbon footprint. When you burn that same tree all that negative carbon footprint turns into NOTHING.

The tree already cleaned the air for the 100 years it lived. The few hours of burning put the carbon back in the air the tree already took out. It does NOTHING.

Charcoal is good for the earth and the microorganisms in the soil.
It is being practiced in many countries all over.

All we need to do is till the soil and spread synthetic fertilizer to grow anything so........

About the ph. If it is ash it will increase ph and add sulfur. If it is washed bio char then it has 7 ph and nothing in it. I made to use as perlite replacment before. If you use it in the field you will not wash it. Spread it light and it wont hurt ph.

I dont know what your soil is like or how much compost u use, but I read something about a field that had so much goat manure on it the over use of ash did nothting to the plants even with a soil test of 8 ph. The natural buffering of the manure allowed all nutrients to be used no matter the ph.

This post was edited by TheMasterGardener1 on Tue, Dec 25, 12 at 17:50


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RE: pH question: charcoal as soil amendment

The smoke from wood burning stoves, or from a brush pile since it makes no difference where the pollution comes from, triggers an Asthma attack in those of us with Asthma. Numerous studies have shown that buring wood, even in a wood burning stove, produces large amounts of pollution that are a health hazard even to those that do not have Asthma.
Never spread wood ash on your soil without knowing what your soils pH is along with the numbers for Calcium and Magnesium.

Here is a link that might be useful: About wood smoke pollutants


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RE: pH question: charcoal as soil amendment

Diesel combustion is easily the worst contributor of dirty pollution all over, since diesel rigs are everywhere; coal is the worst in absolute terms. Let's be glad we have nowhere to live but industrial China.

These slow-motion regurgitative arguments are amusing in a deja-vu manner...


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RE: pH question: charcoal as soil amendment

Burning wood does NOTHING to the environment.

Come out and spend a week down-wind from one of our major forest fires, then get back to us.


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RE: pH question: charcoal as soil amendment

whether smoke from a power station or a home fire they are adding pollutants, then the mythology comes in and claims that all that and exhaust fumes (smoke) mess up the climate, not so of course but those who promote it have the ears of the world.

what mayan's, inca's or aztec's may have done as the cleared and burned is nothing more than myth now named bio-char and terra preta. they just simply buried their ash.

so if you can source ash that is not specially made ie.,. fireplace stove etc.,. use it the pollution is already out there, if once sued in your garden it supposedly draws back that pollution or takes down fresh pollution is all again part of the mythology worship.

what i have experienced is that ash (first time i've ever used it) is helping my plants eg.,. egg plants with a good layer of ash below are at least twice the size of others in the same bed with no ash below.

we burnt a lot of trees to get our ash, lots of clear burning happens here where building blocks are around 1 acre. lots of that ash goes to waste and the fires can burn for up to a week.

all i would say is use it, it's all part of recycling for better gardens.

the bio-char proponents seem to make some outlandish claims.

before judging i push no barrows, i make no money and it makes no difference to me what other gardeners may do.

len

Here is a link that might be useful: lens permaculture essay


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RE: pH question: charcoal as soil amendment

"whether smoke from a power station or a home fire they are adding pollutants,"

Although not at the same rate in terms of grams of pollutants per btu's of heat. I hope we can all agree on that.

"..then the mythology comes in and claims that all that and exhaust fumes (smoke) mess up the climate, not so of course but those who promote it have the ears of the world. "

You mean the 95% or so of climate scientists? Mythology? Okey dokey.

Once we no longer believe the scientists and their peer-reviewed research, we're doomed. Just my opinion.

"if once sued in your garden it supposedly draws back that pollution or takes down fresh pollution is all again part of the mythology worship."

I am very curious about this. I don't think anyone in this thread has claimed that biochar somehow draws pollutants back out of the atmosphere. Maybe I don't understand what you are referring to. It would not make any sense, and even though I have seen the benefits of charcoal added to soil, I do not believe in (or worship) such a myth.


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RE: pH question: charcoal as soil amendment

Len's posts tend toward the incomprehensible, Tox. I wouldn't spend much time trying to decipher....


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RE: pH question: charcoal as soil amendment

Yeah, just couldn't help myself. Slow day I guess. :-D


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RE: pH question: charcoal as soil amendment

..
"Once we no longer believe the scientists and their peer-reviewed research, we're doomed. Just my opinion."

I don't see myself departing from tox too often if at all but, I'm becoming more skeptical of science as it comes at me in the broader media today.

I don't have the time or inclination to read all the research on any one thing to decipher exactly what that research tells us and, more importantly, what it doesn't tell us. As science is reported to us in the broader media it is another filter we have to consider when we think we understand the science. There are agendas involved in how science is funded, produced, reviewed and, reported. In the true spirit of science I believe we have to look at science with a wary eye. Once we blindly believe and accept everything anyone has to offer, scientists, salesmen or politicians, we're doomed in my jaded opinion.

to sense
..


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RE: pH question: charcoal as soil amendment

ah but the worshipers of bio-char(a modern tag) do believe that, they state that any pollution they cause whilst specifically making bio-char is negated once they apply the char to their gardens. maybe some time spent in groups like permaculture might reveal to you what i say.

again judgements leveled my way, again i have nothing to sell or promote other than sense and common sense, if you find other please let me know? i support no political parties or affiliations.

neither do i support some of these fringe sciences who exist solely to support a theory that will never be seen as hard copy fact. appears to me those science minded people or their supporters have no real answer to give to others so they denigrate others personalities.

have a great new year

len


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RE: pH question: charcoal as soil amendment

If I have denigrated your personality in my responses, I sincerely apologize, but I don't think I have.

rott: I think the problem lies with science coming 'through the media'. It is indeed a minefield out there, and if you take your science through the mass media...well. I would certainly look with a wary eye - at the media much more than science itself!

It is possible to bypass the talking heads and pundits without having to read 100 journals monthly.


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RE: pH question: charcoal as soil amendment

"Come out and spend a week down-wind from one of our major forest fires, then get back to us. "

Forest fires cause trees to release new seeds, which makes more trees. In some forests, fires are needed.

Trees take pollution out of the air. When you burn them they put back just as much pollution as they took out so it does NOTHING.

:)


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RE: pH question: charcoal as soil amendment

Well, there are forest fires and other forest fires. Right now, most of the Rocky Mountain west is undergoing massive beetle kills, with 2/3 the standing trees dead and ready to burn. Conifer forests are red and grey with dead trees.

Actually, there are a lot of deleterious effects of massive forest fires, particularly in the larger picture where mountain snows feed reservoirs that retain water for people living in arid landscapes. Faster spring runoff, mud and rock slides, and probably the most insidious, enormous amounts of silt and ash - millions of cubic yards - wash down filling dams and swamping crucial infrastructure. With the fires we had this past summer, affected rivers are still running black.

And nothing like spending 6 weeks running around with a dust mask, coughing, wide spread asthma, runny eyes, etc. This pic is just a small example of what much of the pine forests in the west looks like:


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RE: pH question: charcoal as soil amendment

An air quality study was done around here back in the 1970's and those doing the study found that in the fall, when people were burning leaves, major pollutants increased greatly (this when we still had grey iron foundries working) and during the winter when people were using wood burning stoves (this during a surge in popularity of those) the same thing happened. That data was what convinced our county board of commissioners to approve a county wide burning ban.
I was a firefighter/EMT at the time and we had an increase in calls for Asthma and COPD patients during those times due to the pollution this burning produced. Today as one with severe Asthma and emphysema, COPD, I know very quickly when someone fires up their wood burning stove because I start having even more trouble breathing, even inside my house because there is no way to keep those pollutants out.
Burning wood wastes most of the nutrients that would has, although the resulting ash, or charcoal, will have the minerals in a more readily available form. Even in a modern wood burning stove the amount of pollutants released is very high.


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RE: pH question: charcoal as soil amendment

Redwoods ONLY release seeds After a FIRE.


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RE: pH question: charcoal as soil amendment

Good for the redwoods. :-)

However, the problem here is that these intense fires in over-crowded forests - the result of clear-cutting followed by decades of fire suppression - now accentuated by drought, billions of beetle-killed dead trees, and a 70 day longer (at least) forest fire season - add some strong winds and the result is a sterilized landscape.

Which is why following these intense fires, there is a huge push to get native grasses and such planted before the noxious weeds blow in.


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RE: pH question: charcoal as soil amendment

I agree that most wood burnt is done so in an inefficient manner. With severe asthma can you not also detect diesel smoke and when down the street a dirty oil-burner fires up? I certainly can. A difference from wood is that burning heating oil does not leave a useful garden soil improver.


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RE: pH question: charcoal as soil amendment

So if in the process of making that "useful garden soil improver" you send one, or more, people to the hospital that still justifies what you did? If in the process of making that "useful garden soil improver" you contribute more CO2 that increases the rate of global warming that justifies what you did?
What about all of the nutrients that you burned up in the process of getting that questionable "useful garden soil improver" that is so soluble that the change in the soil does not even last a full growing season?


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RE: pH question: charcoal as soil amendment

"""useful garden soil improver" that is so soluble that the change in the soil does not even last a full growing season?"""

this whole statement is redundant, otherwise the Amazon black soil wouldn't exist to date.


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RE: pH question: charcoal as soil amendment

Man, arguing with you is like tilting the windmill. Just around and around. I got time to burn I guess, as you do.

If you are asking if I personally feel guilty about burning wood, the answer is no, I don't. Again, I'll explain to you that we are all heating our houses via combusting some hydrocarbon somewhere. I burn wood much more efficiently than most people do, and more efficiently than most coal-burning electrical plants (lucky you don't have to breathe air down-wind a few miles of one of those disasters), and more efficiently than many heating oil burners. I burn wood hot. Most people don't, because they don't have the equipment that allows it.

What nutrients am I releasing into the atmosphere, BTW?


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RE: pH question: charcoal as soil amendment

..
pnbrown - I'm curious now. What kind of wood burning contraption are you using? I have a passive interest in different methods is all.

Thanks in advance
..


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RE: pH question: charcoal as soil amendment

unless you're heating your house by wind or solar I don't see how anyone is not adding to the pollution of the atmoshere.


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RE: pH question: charcoal as soil amendment

darth: exactly.

rott: I use a masonry stove that I built, simply a pile of mass capable of absorbing the heat from a wide-open burn for several hours. Mine is fairly small because the climate here doesn't call for day-long burns, but one can build it with as much mass as required. Of course if one tries to burn fully hot and efficient in any kind of metal stove one will melt down the stove and/or cook everyone out of the building.


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RE: pH question: charcoal as soil amendment

pnbrown,

I agree with you all the way here!


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RE: pH question: charcoal as soil amendment

darth weeder,

Even with wind and solar power there is a fairly large startup of manufacturing...like those windmills don't sprout up out of the ground. I also see all of those access roads to the windmills and around here, they have placed them on the very best farmland it seems.


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RE: pH question: charcoal as soil amendment

Wayne I'm guessing we're all guilty of killing the Earth in one way or another then. lol


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RE: pH question: charcoal as soil amendment

I have no doubt that if we all heated our houses with wood, the atmosphere in colder climates would be much more polluted than it is.

However, technology has improved vastly since the 1970s. Those studies led to emission standards for stoves. Both of mine have catalytic converters, and are supposed to put out <1 g of soot per hour. Granted, that is not zero.

In my case I think I'm the only one for several blocks around who heats with wood, so I don't think it's significant.

I do give myself credit for having thought about the pros and cons, rather than just cranking the thermostat.


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RE: pH question: charcoal as soil amendment

Posted by darth_weeder z7 NY (My Page) on Tue, Jan 1, 13 at 15:16

"Wayne I'm guessing we're all guilty of killing the Earth in one way or another then. lol"

Its called 'greenguilt'

This post was edited by TheMasterGardener1 on Wed, Jan 2, 13 at 14:51


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RE: pH question: charcoal as soil amendment

Or, in its healthy form, it's simply being thoughtful about our footprint. Ignoring the surroundings has caused the demise of many a civilization.


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RE: pH question: charcoal as soil amendment

"If in the process of making that "useful garden soil improver" you contribute more CO2 that increases the rate of global warming that justifies what you did? "

Again, this is a falsehood that gets repeated over and over. Trees are part of the carbon cycle. They take CO2 out of the atmosphere to build their tissue, and the CO2 is returned to the atmosphere when they decay. This has absolutely nothing to do with 'global warming.' The CO2 of concern to scientists is that which has been locked up for millions of years underground in the form of petroleum, natural gas and coal. When any 'fossil fuel' is burned, it returns carbon to the atmosphere that has not been there in geological times (millions of years). The burning of wood, on the other hand, only releases CO2 that was in the atmosphere within the lifetimes of ourselves and our parents. Totally different.


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RE: pH question: charcoal as soil amendment

Absolutely correct.


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RE: pH question: charcoal as soil amendment

Thank you jonfrum, you backed what I said. If you read back I already said that. You worded it very nice though. :) It is fun being right.


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