....and/or if you have cheap renewable electricity, use it to make C-negative
electrolytic H2 - as much as 50 tonnes CO2 consumed and avoided per tonne H2.
Intermittent RE? use the H2 for energy storage, and with fuel cells, put e back
on the grid when electricity demand/supply peaks. Cost? Assuming an RE cost of
$0.06/kWh (wind?) and a market value of H2 of $1.50/kg, I get a CO2 mitigation
cost (CDR + CO2 avoidance) of $77/tonne. At $0.03/kWh, I get $41/tonne CO2
mitigated. This does not include the $ benefit of alkalizing the ocean (saving
corals, etc) with the dissolved mineral (bi)carbonate formed. And/or if you
insist on growing algae, feed the dissolved mineral bicarbonate to (carefully
managed) algae cultures since HCO3- uptake rather than CO2 uptake is the
primary way marine algae acquire carbon, plus you don't acidify the cultures by
adding CO2. ;-)
Greg
From: Charles Greene <[email protected]>
To: Peter Eisenberger <[email protected]>
Cc: [email protected]; "Hawkins, Dave" <[email protected]>;
"[email protected]" <[email protected]>; geoengineering
<[email protected]>
Sent: Sunday, September 17, 2017 11:14 AM
Subject: Re: [geo] Swanson's law
Co-locating DAC and PV or concentrated solar with commercial-scale, marine
microalgae production facilities would provide onsite supply of electricity and
CO2 without the release of any additional emissions of fossil carbon. In
addition to producing fossil carbon-neutral liquid fuels and nutritional
products from the microalgae, the production of plastics and other biopetroleum
products for the human-built environment could lock up carbon while generating
revenue. This might be preferable to DAC and subsequent carbon sequestration in
geological repositories. The market for carbon-negative biopetroleum products
is not of sufficient scale at present to create a large dent in the amount of
carbon that will need to be stored. However, the infrastructure required for
the human-built environment is enormous, and we would just need to be clever in
how we substitute materials.
On Sep 17, 2017, at 1:49 PM, Peter Eisenberger <[email protected]>
wrote:
I agree with this 100%
On Sun, Sep 17, 2017 at 7:14 AM, Michael MacCracken <[email protected]>
wrote:
A problem at present is that present high-voltage/alternating current
distribution lines mean that low-cost transmission of electricity is limited to
a few hundred miles, so one would have to disperse DAC. If instead there were
large-scale high-voltage/direct current distribution lines (see MacDonald et
al., Nature, January 2016), then there could be long distance, low-cost
transmission over large distances and one would have a much better likelihood
of having access to any stranded energy (from wind, solar, geothermal,
nuclear, etc.), all while having DAC located where it would be optimally able
to store the captured carbon. Just another reason, among many, for having
large-scale HV/DC networks across the world's continents.
Mike MacCracken
On 9/17/17 10:50 AM, Hawkins, Dave wrote:
Using stranded renewable energy for DAC is an interesting idea. Question is
what energy resource will be used during periods when there is no surplus RE?
If DAC does not run 24/7 its costs go up. If DAC uses RE to run 24/7, that
requires a larger RE system with associated stranding. If DAC uses something
other than RE, what is it? Ideally, we would have an economically dispatchable
zero-carbon resource. This is not an argument against DAC, just an observation
on system complexity.
Sent from my iPad
On Sep 17, 2017, at 3:58 AM, Andrew Lockley <[email protected]> wrote:
Does anyone have a breakdown of projected input costs for Direct Air Capture?
I'm interested in quantifying the energy component.
Swanson's law predicts reliable falls in the cost of solar. Without storage,
much peak-time solar could be wasted, unless it's used for time-insensitive
applications like DAC or desalination.
(I understand Keith's process needs electricity, but Lackner's instead needs
heat.)
My hypothesis is that DAC could become vastly cheaper, if energy costs
trended down as expected due to Swanson's law, and cheaper still if it became a
way to use this stranded energy.
I'd welcome thoughts, data, projections and comments.
Thanks
Andrew Lockley
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