Simply grinding rocks would in certain settings accelerate CDR (Harvey, 2008;
Schulling et al.), but to meaningful do this would require spreading over large
land or ocean areas, with significant transport costs, large land/ocean
footprint, and some chance of non-trivial environmental impacts. Placing this
material on high-respiration/acid soils could further intensify the weathering
and CDR, to the potential benefit of plants/crops/biomass production
(synergistic with biofuels/biochar?). Value comparison between this approach
and more intense/artificial weathering schemes would probably come down to the
$, environmental, and societal cost of managing huge land/ocean areas vs more
capital intensive but much less area intensive artificial acceleration methods.
Need some funding/workshops to evaluate this.-Greg
--- On Fri, 3/9/12, Andrew Lockley
<[email protected]> wrote:
From: Andrew Lockley <[email protected]>
Subject: Re: [geo] Rapid ocean acidification militates rapid CO2 removal (CDR)
To: [email protected]
Date: Friday, March 9, 2012, 11:10 AM
What I was meaning on the mineralisation was the use of the additional ions as
opposed to the basic crushing process. Surely you'll be breaking the rocks?
This will accelerate weathering anyway. Maybe your process is faster per tonne,
but what's the dollar efficiency?
Maybe reply to list?
A
On Mar 9, 2012 5:55 PM, "RAU greg" <[email protected]> wrote:
Thanks, Andrew. To answer your questions:1) This is not an energy generation
scheme, it is an energy consumption scheme (as is most CDR), but where some
useful things are done when powered by non-fossil energy: CO2 consumed, H2
generated, ocean alkalinity is increased. You can then do some useful things
with the H2: hydrocarbons, electricity, water. Furthermore, given the abundance
of the required ingredients, this can scale. The central issue (as in most CDR)
is economics: this isn't free, but is also is not going to cost $1000/tonne CO2
as in the case of DAC analyses (House et al; Socolow et al.), primarily because
I am not making concentrated (and risky) molecular CO2. I think the cost is
more like $100/tonne CO2, especially depending on the local market value of the
ingredients needed and the by-products/services produced (e.g., what is the $
value of freshwater in a desert? what is the $ value of
neutralizing/offsetting ocean acidity - how much do we value coral reefs?)
2) Certainly we can let nature take it's course and let natural mineral
weathering consume all of the CO2 we care to emit, ultimately generating ocean
alkalinity and neutralizing ocean acidity. But this will take on the order of
100kyrs to achieve, and that's after we stop emitting CO2. Waiting around for
this to happen could be catastrophic. So might there be economically and
societally acceptable ways to accelerate this inevitable, effective, but
otherwise very slow mitigation?
-Greg
--- On Fri, 3/9/12, Andrew Lockley <[email protected]> wrote:
From: Andrew Lockley <[email protected]>
Subject: Re: [geo] Rapid ocean
acidification militates rapid CO2 removal (CDR)
To: [email protected]
Date: Friday, March 9, 2012, 12:10 AM
Why would you electrolyse sea water to make h2 to generate electricity? Isn't
that a bit circular?
Why would you use electro chemistry to accelerate weathering when you can just
let it progress naturally?
A reply to list might be helpful.
A
On Mar 9, 2012 5:40 AM, "RAU greg" <[email protected]> wrote:
John,
Not sure what solar powered process you are talking out, but re CDR and OA, it
is possible to generate carbon-negative H2 electrochemically using base
minerals (limestone or silicates), seawater, and photovoltaic Vdc *. The
neutralization of the acid normally produced at the anode of a seawater
electrolysis cell (neutralization by the presence of base minerals) forces
excess OH- to accumulate in the seawater, which rapidly reacts with air or
ocean CO2 to form alkaline bicarbonates. Thus CDR is effected in seawater, and
ocean acid is neutralize and/or the added alkalinity helps offset the effects
of ocean acidification (by elevating carbonate saturation state).
As for fuel, it would be most efficient (carbon- and thermodynamics-wise) to
directly use the H2 that is produced at the cathode, but if you insist on
clinging to hydrocarbons, yes there are schemes for making these from H2 and
CO2. The hydrocarbon utilization route of course just keeps more C circulating
in the atmosphere. Keep in mind that using fuel cells, H2 can be readily
converted to electricity and pure H2O, the value of which would not be lost on
your present (and wanabe) coastal desert dwellers.
Given the global abundance of seawater, base minerals, photons, and silica (for
photocells; or one could go the solar thermal - electricity route), the
preceding should scale quite readily, with relatively small land footprint(esp
small if one considered using offshore solar or wind). One little problem is
the avoidance of Cl2 generation at the anode, but there have been
demonstrations of O2-selective anodes and other schemes that could be relevant.
Let me know when you are ready to save the world or at least terraform some
coastal deserts ;-)
Regards,
Greg
*http://www.goldschmidt2011.org/abstracts/finalPDFs/1698.pdf
http://pubs.acs.org/doi/pdf/10.1021/es800366q
--- On Tue, 3/6/12, John Nissen
<[email protected]> wrote:
From: John Nissen <[email protected]>
Subject: [geo] Rapid ocean acidification militates rapid CO2 removal (CDR)
To: "geoengineering" <[email protected]>
Cc: "John Nissen" <[email protected]>, "Peter R Carter"
<[email protected]>, "Anthony Cook" <[email protected]>, "Ron Larson"
<[email protected]>, "Sam Carana" <[email protected]>
Date: Tuesday, March 6, 2012, 6:02 AM
[Resent with correction] Hi all, Is there an alternative to rapid CDR to reduce
the atmospheric CO2 level
and hence slow ocean acidification? Acidification is progressing at the
fastest rate for 300 million years, faster even than in the PETM [1],
and spells catastrophe if not curbed over the next decade or two.I am supporter
of biochar for CDR on a large scale. But few people
think biochar can be scaled enough to actually start reducing the
atmospheric CO2 level in the face of CO2 emissions set to climb for
decades. So we need a combination of low to medium cost CDR schemes,
capable of scaling to the very large.
Yesterday I heard about a scheme for use of solar energy (e.g. in Sahara) to
power the scrubbing of CO2 from the atmosphere and the production of hydrogen
from H2O. The hydrogen would then be combined with the captured CO2
to create a carbon-neutral hydrocarbon fuel, which could then be cheaply
and efficiently piped to countries wanting a green energy source, e.g.
for cars and electricity generation. Apparently it's much cheaper and
more efficient to pipe liquid fuel than transmit the equivalent electric
power over the same distance. Cheers, John P.S. If hydrogen can be produced
from H2O, could a hydroxyl byproduct be used for
combination with scrubbed methane (CH4) to produce further
carbon-neutral fuel? Atmospheric methane levels are rising ominously. [1]
http://planetark.org/wen/64838
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