Ken (cc List)
It is fine by me to ignore the first 5 entries below.- or read them last.
1. I believe your suggested 3-way, 8 box approach has merit. This is to comment
on it as a Biochar proponent, but not claiming to speak for the technology.
Others are sure to have other thoughts
2. Before trying to fit Biochar into your proposed scheme, let me add three
other characteristics that are important to Biochar folk, and that don't apply
to most of the other CDR approaches.
First is the value of Biochar in soil improvement - well established by what we
know of the Amazon's Terra Preta history. This asset is shared to some extent
by no-till, but that technology's much shorter soil C-lifetime means that it
only rarely appears in CDR listings.
Second is that Biochar provides several unique out-year benefits. It can be
seen as an investment rather than an expense. This is sufficiently unique that
it can't /shouldn't (?) be used for comparisons. It is a characteristic also
that makes LCA much more difficult.
Third is that Biochar provides important "carbon"-neutral service for N20 and
methane, that needs some recognition.
Fourth is that Biochar inherently provides carbon-neutral energy as well as
carbon-negative, energy-consuming sequestration. This property is shared only
(?) with BECCS.
3. Let's identify your 8 categories with base-2 nomenclature from 000 to 111,
in exactly your order (and other orders might be better).
A left-most bit = 0 denotes biological (Bi) approach, and 1 means chemical
(Ch).
For the middle bit, a 0 is central (Ce) and a 1 is decentralized (De).
For the right-most bit, a 0 is oxidized (Ox) carbon and a 1 is reduced (Re).
4. Perhaps surprisingly, I find only the right-most bit to be un-complicated. I
believe there will be agreement that all Biochar can be considered as reduced
carbon (right bit = 1, (odd numbers) as we are talking final disposition is as
C, not CO2). {Note - I changed my mind on this - see later)
For the middle digit, I think Biochar might qualify under both central and
decentral, depending on how this is defined. Most activity is now decentral,
but I can conceive of a most-economic collection radius as large as 15-20 km -
which some will term "Central"..
For the left-most digit, I think most would define Biochar as a biological
approach, but the conversion approach (usually pyrolysis) is primarily the
world of chemical engineers. There is major disagreement on what the optimum
transformation temperature should be for different soil types/ There are
options for working with liquid, gaseous, and solid (electric power)
co-products. This results in co-products that differ a lot in their chemical
characteristics. The technology called HTC (HydroThermal Carbonization) is
especially different - and potentially an optimum for liquid wastes. (See
http://www.biochar-international.org/search/node/htc).
5. Now, per request, trying to populate the 8 CDR "boxes"
000: 0 ; BiCeOx BECCS
001 1 ; BiCeRe Large scale Biochar, Forestation (? - not really reduced); Ocean
fertilization (not really reduced), burial of biomass (land or oceans)
010 2 ; BiDeOx
011 3 ; BiDeRe Small-scale Biochar , Individual-level Forestation (?)
100 4 ; ChCeOx DAC; Enhanced weathering; maybe some BECCS;
101 5 ; ChCeRe ( Biochar as minor part of some forms of energy conversion?)
110 6 ; ChDeOx (maybe some DAC?)
111 7 ; ChDeRe (Biochar unlikely?)
6. MY conclusion after this exercise is that a possibly more helpful means of
separating is into 4 "boxes" - all related to a single characterization that is
different from your three. That characterzation is through the ultimate form of
the sequestered carbon (a wider range than your "reduced" and "oxidized").
There is nothing special about this ordering..
1. As CO2 - (always liquid CO2-oceans or deep underground sequestration?)
a. DAC, b. BECCS
2. As C - starting only from biomass (with low or zero oxygen conversion)
a. Biochar
3. As relatively unmodified biomass (any combination of lignin, cellulose,
hemi-cellulose, starches, sugars, etc)
a. Forestation, b. useful long-lived biomass products, c. land burial of
biomass, d same in ocean, e. ocean fertilization
4. As carbonates, bicarbonates, and similar , not starting with biomass ;
(always starting with conversion of CO2 ?)
a. Enhanced weatherization
7. I am also suggesting from this brief alternative exercise that central and
decentral (the middle bit) are not a helpful differentiator. Biochar (type 2)
and Forestation (type 3) may be the only ones that can be decentral.
8. Your first (Bio and Chem) and last (Oxidized and Reduced) divisions lead to
something somewhat similar - but apparently not the same. For my new category
"1" combines DAC and BECCS - which are in different boxes in the 8-box
approach. Mostly though I had trouble deciding where to place the items 3 and 4
into the "reduced" and "oxidized" categories that work nicely for only DAC,
BECCS, and Biochar.
9. It wouldn't surprise me that there is an appropriate fifth category, by
breaking out the word "similar" in "4". More thought should be given to the
ordering of the 4 or 5 categories above
Sorry this is so rambling. I ran out of time. Ron
----- Original Message -----
From: "Ken Caldeira" <[email protected]>
To: "geoengineering" <[email protected]>
Sent: Thursday, March 29, 2012 3:40:57 AM
Subject: [geo] Taxonomy and nomenclature for carbon dioxide removal (CDR)
methods
I'm starting this as a new thread, because this conversation was getting
embedded in another thread ...
Almost every carbon dioxide removal method by definition directly captures CO2
from the atmosphere, and thus they may all be thought of as some form of direct
capture of CO2 from the air.
As a result, the acronym DAC (for Direct Air Capture) has in some case led to
unclear communication as some people are using Direct Air Capture to refer only
to centralized chemical-industrial facilities that remove CO2 form the
atmosphere and others, apparently, have been using term to refer more broadly
to nearly all carbon dioxide removal (CDR) approaches.
It would be useful to have some clear and consistent terminology to avoid such
confusion.
Important dimensions to consider are:
1. Biological vs. chemical approaches (Are you using plants to do your capture
for you or are you using some sort of chemical process)
2. Centralized vs. distributed approaches (Is the approach deployed in a
centralized facility or does the capture from air occur across broad extents of
land and/or ocean surface?)
3. Is the carbon stored as oxidized (molecular CO2, HCO3-, etc) or reuced
(organic carbon, black carbon)?
These three binary choices suggest eight categories with limitless
possibilities of sub-categories.
So, for example;
-- Centralized industrialized direct air capture is investigating (1) chemical
approaches that are (2) centralized and (3) store the carbon as molecular CO2
[oxidized].
-- Ocean fertilization is (1) biological approach that is (2) distributed and
(3) ultimately stores the carbon as HCO3- [oxidized] carbon in the deep sea.
-- Biochar is a (1) biological approach to capture that is (2) distributed and
seeks to (3) store the carbon as reduced carbon.
-- Liming the ocean is a (1) chemical approach that is (2) distributed over a
wide area and (3) stores the carbon as oxidized carbon (HCO3-).
-- Afforestation is a (1) biological approach that is (2) distributed over a
wide area and (3) stores the carbon as reduced [organic] carbon.
Which of these 8 basic categories are populated? Do we have clear an
unambiguous terms to refer to each of the populated categories? I think not.
There are no feasible centralized biological approaches because photosynthesis
by its very nature involves large areas to capture enough sunlight to be
quantitatively important.
_______________
Ken Caldeira
Carnegie Institution Dept of Global Ecology
260 Panama Street, Stanford, CA 94305 USA
+1 650 704 7212 [email protected]
http://dge.stanford.edu/labs/caldeiralab @kencaldeira
YouTube:
Climate change and the transition from coal to low-carbon electricity
Crop yields in a geoengineered climate
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