h a l f b a k e r yCogito, ergo sumthin'
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Concrete production is one of the major contributors to
anthropogenic CO2 emissions. It’s unavoidable, it’s right
there in the chemistry. Roughly 180kg of CO2 per tonne of
concrete, equivalent to 50kg carbon.
Concrete incorporates cement, sand and aggregate
(gravel). Adding 50kg per tonne
of Biochar/carbon might
have a minor effect on strength and curing, but this will be
small and might even be positive (as a result of
microstructure/surface area effects)
Most concrete structures are massively over-strong anyway.
Even accounting for carbon emissions in producing Biochar,
the result would be concrete that was a net sink of
atmospheric carbon, as opposed to a net source.
Some research into mechanical and curing behaviour
required.
Alternate chemicals for cement
https://qz.com/1123...ing-it-heres-a-fix/
magnesium oxide and wollastonite [discontinuuity, Oct 17 2019]
Concrete made from iron and glass
https://www.greenbu...cled-glass-concrete
"An experiment with silica and rusty iron led this researcher to what some are saying could be the first really promising low-impact substitute for Portland cement" [discontinuuity, Oct 17 2019]
Plastic waste in concrete mix
https://phys.org/ne...tainable-india.html
"Waste plastic in concrete could support sustainable construction in India" [discontinuuity, Oct 17 2019]
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Yes, but why put the biochar into the concrete? It is of no
benefit to the concrete, and is potentially deleterious. Much
better to plough the same 50kg of char into poor soils - you
lock up as much carbon, don't weaken the concrete, and
improve the soil. |
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Activate the charcoal to make bio-char and create terra preta which binds up carbon for a thousand years providing the teensiest of niches for bacteria to produce mega rich top soil several feet deep. |
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Figure out how to make tiles out of bound carbon and you've got a winner. |
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It seems to me that as long as there is a single coal mine
still in operation, making biochar for the purpose of
sequestering carbon (or probably just about any other
carbon sequestration method) is a complete waste. It
would be far better to leave the coal buried deep
underground where it was formed and just burn the
biomass for energy. It appears that in the US there are
178 biomass power plants (total 6374.75 MW), though
maybe half to three quarters of these are currently
running off of municipal solid waste. |
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Interesting note: according to google, the cost of coal is
$39 per ton and the cost of biochar is about $2580 per
ton. If just 2% of the cost of Biochar is going to pay for
the energy to shred, transport, heat, etc, it may be that
you're releasing more carbon than you're sequestering. Or
maybe the supply/demand is just really messed up right
now. |
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My first thought was that you were going to put diamonds in
as part of the aggregate. |
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Totally agree about using Biochar in the soil. $2580
doesn’t sound like a real price. In the UK you could
make Biochar for around £100/tonne. |
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//UK you could make Biochar for around £100/tonne// |
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Biochar has problems with low density, it could migrate in
the mix, it's porous with inconsistent gas pockets and can
contain varied mineral deposits. Instead, use a nice
Anthracite coal. Crystaline, high-strength, high carbon,
relatively pure, much cheaper and the carbon is biologically
sourced from the atmosphere before a careful ageing
process. |
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If burned properly retort the off gas could be collected and burned for fuel as it once was before finding natural gas deposits. |
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It's completely retorted... |
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Why not just construct buildings out of wood instead of concrete ? |
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The downside is that wooden buildings burn really well. |
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However, the upside is that wooden buildings burn really well ... |
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//wooden buildings burn really well ...// |
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Providing a supply of biochar... |
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There have been several proposals to make cement out of other chemicals in order to absorb CO2, including magnesium oxide, iron oxide, and the mineral wollastonite (see links). None have had commercial success. There have also been attempts to add plastic waste to concrete. |
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//as long as there is a single coal mine still in operation [etc.]// |
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You're assuming some sort of global unity of human purpose;
it's a bit like arguing that no-one should fight fires so long as
there are arsonists, isn't it? |
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What if it wasn't intentional ? What if it's just a case of playing with matches or a lighter, and maybe a can of butane gas, and some kerosene, and it all got a bit out of hand ? No intent to do harm just a craving to see the gorgeous golden-yellow flames curl and dance, a beautiful coruscating ballet of light and destruction ... |
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// You're assuming some sort of global unity of human
purpose; // No I'm saying that if there's a coal power
plant in some other city, state, or foreign country, if you
GIVE them money to build a new power plant, the money
will be much better spent there than building a biochar
plant big enough to compensate for the coal power plant.
Even if they object to loosing all those coal mining jobs,
offer to buy all their coal production and rebury it. That
sounds wasteful, and stupid, right? But it's less wasteful
than burning the coal at a 37% efficient utility scale
power plant, then producing biochar to compensate at a
presumably even worse efficiency. |
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//it's a bit like arguing that no-one should fight fires so
long as there are arsonists, isn't it?// No because you
can't pay arsonists to stop setting fires. I haven't heard of
anyone who wants to keep coal power plants in operation
for any reason besides economics. If you offer them
enough money to switch, they will. Okay, maybe North
Korea would be resistant, but if you can get the money to
them in some way that they can save face and brag about
their new modern power plants, I'm sure you could make
that work too. |
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// maybe North Korea would be resistant, // |
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Not if you offered them free nuclear powerplants... |
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