Please simplify. How much carbon on how much land?

[Philip Small]

What is the maximum reasonable charcoal input on a given acre of land?

 

Considering the theoretical scenario presented, you could reasonably add charcoal at 1 ton/acre/year. forever. to any reasonable soil, not just agriculture. Considering that charcoal could reasonably be employed in strategies to vegetate non-soil and disturbed soil areas (active sand dunes, recent lava flows, badlands, damaged and degraded landscapes) it is reasonable to cast a wide net when defining what qualifies as "a given acre".

 

The surface 3.3 inches of mineral soil weighs about 1 million pounds per acre (calculated as 2.65 gm/cm3 (quartz IIRC) * 50% soil porosity * 2.72 million pounds water per acre foot. Note: clays are lighter, sands are heavier due to 60 and 40 percent porosity, respectively)

 

so a ton of charcoal per acre would increase soil charcoal content in a typical mineral soil by 0.2 percent, or 2 g/kg, in the top 3.3 inches.

 

At 5.05 lbs/ft3, 1 ton/acre of charcoal would be 1 tenth of an inch deep.

 

Revised per corrected conversion for lbs/ft3

[Philip Small]

How much agricultural land in the world do we have that we could reasonably use for Terra Preta sequestration?

 

According to this source, of 1.5*10^8 km2 land, 30% is good for agriculture. If we add in the topsoil-less land, the dry land and 1/2 the mountains, we increase terra preta reasonable candidate land to 70%, or 1.05*10^7 km2.

 

This is equivalent to 2.72*10^6 mi2, or 1.74*10^10 acres

[Philip Small]

What is the net annual increase in [excess] carbon?

 

Around 24.126 billion tonnes of CO2 are released from man made carbon dioxide sources per year worldwide, equivalent to about 6.6 billion tonnes of carbon.

[Turtle]

Considering the theoretical scenario presented, ....

 

At 15 lbs/ft3, 1 ton/acre of charcoal would be 3 hundredths of an inch deep.

 

Oh? What size of particles, theoretically speaking of course? You have failed to address my objection as if the particle size doesn't matter to the calculation.

 

Suppose we also start to calculate the energy required to make, grind, transport, spread and till-in said variable weight-per-unit-volume charcoal, and time plus cost ? :hyper:

[Philip Small]

Oh? You have failed to address my objection as if the particle size doesn't matter to the calculation.

 

It does matter, but I am not sure how it affects the results. Perhaps the mass is more packed, more dense, in bulk form than in processed form. This would explain your getting a slightly lower value for powder (230 kg/m3) than published values for bulk, but I don't know if that is the case.

[Philip Small]

Work >> 1 cup charcoal weighs 93.272 gms * 16 cups/gallon = 1,492.35gm/gallon * 7.48 gallons/foot³ = 11,162.79 gm/foot³ / 1,000gm/kgm = 11.16279 kgm/foot³ / 2.2 lbs/kgm = 5.07 lbs/foot³ * 27 foot³/yard³ = 136.99 lbs/yard³ * .765 = 104.79 lbs/m³ * 2.2 kgm/lb = 230.5 kgm/m³

 

Your calcs are right, mine are wrong - I'll go back through and correct my lbs/ft3 etc. accordingly. (Good work, Thanks!)

[Turtle]

Your calcs are right, mine are wrong - I'll go back through and correct my lbs/ft3 etc. accordingly. (Good work, Thanks!)

 

You're a good sport Phillip. :hihi: I was getting so many contradicting calculations last night I wasn't sure of the correctness of any of them. :doh:

 

Oh? You have failed to address my objection as if the particle size doesn't matter to the calculation.

 

It does matter, but I am not sure how it affects the results. Perhaps the mass is more packed, more dense, in bulk form than in processed form. This would explain your getting a slightly lower value for powder (230 kg/m3) than published values for bulk, but I don't know if that is the case.

 

First, my value of 230 kg/m3 is before the crushing, so the powder is 1/3 again heavier than the 2-3cm chunks. I think this affects 'things' because if the truck load is made of large chunks, but the chunks have to be broken up before use, then a smaller area of land can be 'treated' with powder than the estimated calculation based on the suppliers quote of 'x tons of charcoal per truck load'. This is presuming the initial estimate is based on mixing the charcoal with soil by volume, but I can't imagine why anyone would mix it by weight. (this matters in regard to terra preta farming; sequestration, not so much.)

 

My biggest objection is the falsity of the title's claim that this is a 'simple' question, i.e.

At the density of lump charcoal how much volume is that total?

. So too, we find the other questions posed in the opening post 'not simple' in spite of that assertion.

 

For the terra preta enthusiast, get some charcoal & get to work with what you got, and then report back. For the save-the-world-from-global-warming-by-sequestering-carbon-as-charcoal enthusiasts, start calculating how much more CO2 is getting released by burning fuels to do all the work necessary to bury huge amounts of charcoal. After all, no good deed goes unpunished. ;) :cup: :cat:

[Turtle]

I have some 'horticultural charcoal' still left, so I weighed it.[bag says Product of USA, Red McLellan Co, Whitney Farms, PO Box 70, Independence, OR 97351, Whitney Farms Organic Garden Products ... :doh: :cat:

 

I went checking at the above site for the specs on their 'Horticultural Charcoal' product, but I found it nowhere there. I sent an E-mail to their Dr. Dirt requesting info on the product (type of wood & temperature used, etc.) & pasted in the link to our terra preta sub-forum. I'll report back on any reply from the good Doctor. :cup: :hihi:

[Philip Small]

For the Save-the-world-from-global-warming-by-sequestering-carbon-as-charcoal enthusiasts, start calculating how much more CO2 is getting released by burning fuels to do all the work necessary to bury huge amounts of charcoal.

 

Agreed. Even with our poor level of understanding of how best to use charcoal in soil, charcoal is currently far more valuable to the planet as a practical soil amendment with a crowd pleasing carbon sequestering kicker than the reverse: a problematic carbon sequestering tool with a soil benefit kicker.

 

Another thread perhaps?

[Michaelangelica]

"I developed this rough back-of-the-envelope calculation of what it would require if one were to [attempt the Virgin Earth Challenge] with the agrichar concept," Radlein explains. "One would need about 7,000 plants each processing 500 tons of biomass per day, which is a large number, but it's not outside the bounds of possibility." Such facilities would produce four parts bio-oil to one part carbon sequestered, so it would rake in money as well as carbon.

. . .

. . .In 2100, if pyrolysis met the entire projected demand for renewable fuels, the process would sequester enough carbon (9.5 billion tons a year) to offset current fossil fuel emissions, which stand at 5.4 billion tons a year, and then some. "Even if only a third of the bioenergy in 2100 uses pyrolysis, we still would make a huge splash with this technology," remarks Johannes Lehmann, a soil biogeochemist at Cornell University and one of the organizers of the agrichar conference.

Good Blog worth a read

Terra Preta - May 18 | EnergyBulletin.net | Peak Oil News Clearinghouse

 

Then again I look at the 90k line up off coal ships off my coast and wonder, "We best get going soon. Perhaps we don't have time to wait for the big end of town."

What is the best home-made or cheap and/or environmentally friendly charcoal maker?

[Gerrit]

Pangolin wrote:

 

As a means of understanding the uses of Terra Preta it would be usefull to know how much we need for the job[/a] i.e. reducing atmospheric CO2 and/or improving farmland. It would be helpful to know this in units that are in use by the layman i.e. cubic yards of charcoal. It would also be usefull to know minimum and maximum usefull application spread rates in acres and or/sq ft. Just like any other soil amendment.

 

I'm with you Pangolin. Does anybody know what are those rates? All I've read somewhere is that researchers are experimenting with rates of 5 to 10 tons/acre...That's the ball park I'm going with until I hear different...