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8/7/2019 A Two-Proposal Review of Geoengineering by Kelly Boyd
http://slidepdf.com/reader/full/a-two-proposal-review-of-geoengineering-by-kelly-boyd 1/13
ATwo‐ProposalReviewofGeoengineering
Methods
andabriefrecommendationtoresolveglobalwarming
ByKellyBoyd
PREPAREDFOR:
PROFESSORREBECCAJ.BARTHELMIEPH.D
DEPARTMENTOFGEOGRAPHY
PHYSICALMETEOROLOGYANDCLIMATOLOGY
GEOG‐G532
SPRING2011
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1
According to the Institution of Mechanical Engineers, geoengineering is an approach to
resolve climate change that involves large-scale human intervention in the Earth’s climate
system by means of technology and man-made production.1 They continue by saying
geoengineering can be done in one of two ways by: (i) either removing greenhouse gases
directly from the atmosphere (ii) or reducing the amount of solar radiation that is absorbed by the
climate system.1
This essay will highlight these methods of geoengineering by describing two
different types of proposed technology. In these two analyses of geoengineering technology,
their feasibility in terms of building the technology, the utility of their functionality at reducing
global warming and their reversibility will be examined. Next, their economic cost to society
and a brief explanation describing how large of an expected impact this technology will have on
the global mean temperature once instituted will be discussed. Finally, a solution to global
warming will be reviewed using a combination of technology and other resolutions.
Artificial Trees to Reduce CO2 in the Atmosphere
The mention for large-scale carbon sequestering technology was brought to the attention
by leading climate scientist Wallace S. Broecker’s in his book Fixing Climate.2 He discussed
that “the need for carbon scrubbers to cycle carbon out of the atmosphere and back into the
earth’s crust where it belongs is necessary.”2With guidance from Dr. Klaus S. Lackner, a
professor of geophysics, earth and environmental engineering at Columbia University, and Dr.
Broecker’s colleague, pioneered the idea of an artificial tree (sometimes referred to as a “sodium
tree”).3 Years later, Dr. Lackner founded Global Research Technologies (GRT) to help find
better ways to improve the process of carbon capture from ambient air.3 In proposed drawings,
the artificial tree first looked like a large tube sticking out of the ground. He first called it an “air
extractor.”3 After further development and with the help of colleagues, a visual example of an
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artificial tree was rendered (see figures 1-2). The artificial tree and “air extractor” are two
different types of technology proposed by GRT.3
Engineering Feasibility of the Artificial Trees
According to Lackner in 2008, artificial trees can be ready for use within the next two to
four years.3 The standard tree would stand 197 feet into the air and would be able to pivot 360°
in any direction in order to maximize wind flow.4 The first artificial tree prototype developed by
GRT had a patent to use sodium hydroxide resin panels that captures CO2 from its screens.5
But, due to safety issues involved with human handling and cost of sodium hydroxide, a new
technology was developed called the The Atmospheric Carbon Capture Systems (ACCESS™
unit).6 According to Popular Mechanics Magazine, the ACCESS™ unit removes CO2 by having
its screens sprayed with a chemical solution on that bond to the CO2 in the air.6 The solution mix
is then remotely drained off by a PVC pipe system to a separation unit, where the CO2 is isolated
as pure gas through electrodialysis.6 This new form of technology will help reduce the physical
handling of the sodium hydroxide panels. Other than GRT’s ACCESS™ unit of carbon
collection, additional methods of carbon capture are in development using a sodium hydroxide
Figures 1 and 2- Rendered images of air extractors (left) and artificial trees (right)3
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3
spray system or calcium oxide pellets.7 These technologies still need to be researched in their
safety, feasibility and cost to determine if there is a better solution.
According to Dr. Lackner’s technology, the main advantage of the air capture approach is
that it focuses on the reduction of atmospheric CO2 regardless of the source on the planet. It
completes this process through three main stages in the function of the artificial tree:
1. Capture of CO2 from the air into a filter via the ACCESS™ unit2. Removal of the captured CO2 from the filter 3. Sequestering of the removed carbon from the environment until final disposal.9
Of these three steps, long-term carbon sequestering will be the greatest challenge to engineers.
According to a report by the IPCC in 2007, it will take millions of years for CO2 to return to
solid form.8 To solve this problem of natural long-term phase changes (from gas to a solid),
several methods of CO2 sequestering have been examined, but the most feasible is geological
confinement of CO2 in depleted oil and gas reserves across the world.9 Another form of carbon
sequestering currently being researched by Lackner is a process of solidifying CO2 into CO2
rocks by man-made processes.3 Many more years of research will be required to determine the
appropriate technology for CO2 solidification and the means to help handle with potential CO2
leakage from the ground sequestration.
Impact of Artificial Trees and the Reversibility of CO2 in the Environment
The main impact from artificial trees is the obvious reduction of CO2 in the air, a major
component of greenhouse gases (GHG). If a large number of trees are produced, then a
substantial amount of CO2 can be reduced in the atmosphere world-wide. According to Lackner,
artificial trees will be thousands of times more effective than natural trees by removing CO2
faster.9 Lackner also mentions that trees will be most effective along highways, streets, and
major urban areas where CO2 is particularly high in concentration.9 As of 2009, mankind emits
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approximately twenty-nine gigatons of carbon a year of which approximately fourteen gigatons
is produced by transportation.9 With current proposed trees, it would take in the demand of five
to ten million artificial trees to collect 3.6 gigatons of carbon a year.9 But with better technology,
around five to ten million artificial trees scattered around the world would eventually be
necessary to capture all twenty-nine gigatons of annual CO2 emissions. 9 To add, the current
technology of the trees using the ACCESS™ unit only captures and removes less than one
hundred kilograms of CO2 per day, but GRT predicts with future models, trees would eventually
capture one ton per day or at a rate of three kilograms per second (an amount of gas equivalent to
that produced by 20 cars daily).
5, 9
Many more years of research and work need to be done to
better refine the ACCESS™ unit system. If something detrimental, such as a massive decline in
carbon dioxide for plants and other natural processes, then trees can be switched off immediately
and carbon dioxide can be released back into the environment in a controlled manner.
The Cost of Reducing GHG via Artificial Trees
As of January 2011, global mean
GHG concentrations of CO2 are 391.06
ppm (see figure 3).10 In order to reduce
this number to pre-industrial levels or at
the levels at which global mean
temperature will not continue to rise, the
concentration of CO2 would need to be
reduced to 260 - 280 ppm, a decrease in
order of 131 to 111 ppm.8 According to a UNFCCC meeting in Cancun, MX in November of
2010, it would take two gigatons of CO2 to reduce the concentration of CO2 by 1ppm in the
Figure 3- Current GHG Concentrations (Source: NOAA)10
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atmosphere.11 To put this needed reduction in an economic scale, it would cost $10 to $15 trillion
(USD) to reduce the CO2 concentration 50 parts per million worldwide with proposed
technology.4
The monetary cost of manufacturing of artificial trees is expensive, but with newer
cheaper technology and mass production, Dr. Lackner predicts the cost could drop to $20,000-
$30,000 a tree.9
About twenty percent of the cost is accounted for in building the trees with the
remaining amount being absorbed by the sorbent filter materials for carbon filtration.9 The
filtering of CO2 and containment would be an estimate in cost of $300 per ton.4 But according
to Lackner, "In the long term, the price will come down to $30 per ton.”
3
Artificial Trees Effects on Global Mean Temperature
As mentioned earlier, artificial trees will be successful at reducing CO2 in the
atmosphere, which will change the atmosphere’s CO2 concentrations. A reduction in the
greenhouse gas will eventually change the emissivity of earth’s atmosphere. Emissivity is the
percentage of energy radiated by a substance relative to that of a blackbody or the efficiency with
which a material radiates infrared energy.12,13 Emissivity plays a vital role in the global mean
temperature of earth by means of the zero global energy balance model of Earth ( 1− !=
!4
!). The sun allows for shortwave incoming radiation to enter the atmosphere, and in
response, the Earth emits longwave energy to keep the temperature in balance. Sometimes part of
the longwave radiation is absorbed by gases in our atmosphere. This phenomenon describes the
greenhouse effect and properties of emissivity of GHG. In this case, emissivity is a function of
the measure of CO2 concentration in the atmosphere. Based on current averages, the emissivity
of earth is 0.68.14 If CO2 would continue to rise, this number would decrease, allowing for more
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absorption of longwave energy which would cause the global mean temperature of earth to rise.
A slight increase or decrease of emissivity can dramatically affect the earth’s climates. The
last ice age had an emissivity of
0.72, only a 0.04 difference
from current levels.12 To reduce
current global mean
temperatures by 2-6 degrees °C
using the zero-dimensional
energy balance model to solve for emissivity and assuming the following: a global average
albedo of 0.32, a solar constant of 1.37 KW/m², the global mean temperature of 14.5° C or
287.65 Kelvin, and the Stephan-Boltzman constant of 5.67 x 10-8
W/m2K
4, the emissivity would
need to increase anywhere between 0.01 to 0.05 for a 1-6° C decrease in temperature.15, 16, 17, 18
Wind-Driven Spray Vessels to Reduce Solar Radiation
The second type geoengineering technology is the Wind-Driven Spray Vessels that
enhances marine cloud cover to increase
cloud reflectivity of sunlight (see figure
5). John Latham first received the idea
of the spray vessel when “tinkering”
around with marine cloud calculations to
offset global warming in the 1990’s via
the Twomey Effect.7, 19 The Twomey
Effect was noticed by Sean Twomey in 1974 after watching the formation of water droplets in
clouds aided by the presence of ship pollution particles over the ocean over which the water
Temperature (⁰C) Emissivity Increase DesiredEmissivity
Current (14.5) N/A Current - 0.680
13.5 0.008 0.688
12.5 0.016 0.696
11.5 0.024 0.704
10.5 0.032 0.712
9.5 0.040 0.720
8.5 0.049 0.729Figure 4 - A chart representing the increase in emissivity to the degree of degrease in globalmean temperature
Figure5—Arenderingofthewind‐drivensprayvessel20
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droplets can be formed.7 Years later after developing the idea of the spray vessel, Latham
partnered with Stephen Salter a mechanical engineer, and Graham Sortino, a technical
consultant, to formally propose schematics of the spray vessel in a 2008 Royal Society report.20
In the report, they mention how the wind-driven spray vessels will sail back and forth
perpendicular to the prevailing wind and release micron-sized drops of seawater into the
turbulent boundary layer under marine stratocumulus clouds to enhance cloud development over
a large area of the sky.20
Wind-Driven Vessels Impact on Reducing Global Warming
Once the boat sprays water droplets into the atmosphere, they will evaporate, allowing
for cooling and permitting for remaining cloud condensation nuclei (CCN, such as salt) to persist
in the air which would serve as a center of production for additional bigger water droplets to
form.18 These water droplets would eventually form long-lasting clouds over the ocean that
would produce less rainfall.20 This proposed method would possibly increase the number of
water droplets in about ten percent of the world’s marine cloud layers, which would increase the
cloud albedo by 0.06.21 In figure six, the graph depicts other calculations of albedo based upon
the concentration of water droplets and cloud depth for the proposed areas in the Pacific and
North Atlantic Oceans.
These assumptions kept
during the calculations
include: the twenty-four
hour mean solar output
of 340 watts per square
meter, the cloud depth of
Figure6—Cloudtopreflectivityasafunctionofwaterdropconcentrationfor
variouscloudthicknessesanda ro osedli uidwatercontentof0.3ml m319
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300 meters, the boundary layer depth of 1,000 meters, the water droplet diameter of 0.8 microns,
the area of the sea being treated is taken as 18 percent of the total global sea area, and the
average water droplet life in the atmosphere of three days.20 The impact from these clouds will
allow for the ocean and atmosphere to cool within one year.22 The Southern Hemisphere would
see more cooling due to the disproportionate area of ocean compared to the Northern
Hemisphere7. Other possible side effects of the technology could include: a change in rainfall
patterns globally, a change in ocean currents, amplified algae growth on the ocean surface and
salt particulate pollution over certain areas20, 22. If the ships are successful at cooling the planet,
then possible restoration of Arctic sea ice cover could be re-established, the slowing of methane
from the permafrost in the Arctic could be slowed and perhaps renewed saving of coral reefs
could commence.21, 22
Feasibility of the Vessel in Engineering Terms
The forty-five meter boat would be powered by two twenty meter turbines powered by
being dragged through water and controlled by Flettner rotors.23 It will also be operated remotely
without any sails and be designed to not capsize.20 The vessel would also operate as a remote met
station recording atmospheric and oceanic data. The water spray portion of the vessel would
allow for ten kilograms a second of seawater to be sprayed by three four hundred bar pressure
nozzles to allow for water droplets at a size of one micron to be dispersed into the atmosphere.20
Based upon modern technology and trends of growth, these boats will be feasible in engineering
in the near future.
Spray Vessels Economic Cost and Their Reversibility
To begin building a prototype and for tooling the vessel, Latham suggest the initial cost
to be $161 million dollars .22 On the other hand for full production-line deployment, Latham and
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his team estimate a cost of $1.61 - $3.22 million per fully-equipped vessel.22 The team also
calculated that a fleet of 1,500 ships would produce the required volumes of spray to offset a
doubling of CO2 at a cost of $2 -5 billion dollars.22 Latham then proposed that another $1.61
billion would need to be invested in the construction of 300-400 other vessels per year in case of
malfunction, sinking or damage including the infrastructure to conduct maintenance on the
ships.22
If any unforeseen problems arise, spraying could be stopped and within ten days nearly
all of the salt particles would rain or settle out of the atmopshere22. Another aspect to be
researched is the possibility of anthropogenic clouds absorbing solar radiation and causing a
warming from their existence (i.e. Venus).
Effect on Global Mean Temperature
According to Aguado and Burt, albedo is the fraction of solar radiation arriving at a
surface that is reflected.12 In this case, albedo is measured at the top of the clouds and is a
function of the number of droplets, droplet size, and cloud depth (see figure 6). 20 Based upon the
simple zero dimensional energy balance model, 1− !=
!4
!, and solving for α,
scientists can estimate the total change in albedo for a 2-6° C average global temperature change
to be somewhat linear with
temperature (see figure 7). Just a slight
increase of 0.06 in average global
albedo can drop the temperature 6° C.
Again to put this number in
perspective, an average global albedo
increase of only 0.05 caused the last ice age.12 A small increase in albedo can cause a drastic
decrease in temperature worldwide.
Temperature
(°C)
NetChange
increaseinα
GlobalAverage
Albedo
Current(14.5) N/A (Current)0.32
13.5 0.01 0.33
12.5 0.02 0.34
11.5 0.03 0.35
10.5 0.04 0.36
9.5 0.05 0.378.5 0.06 0.38
Figure7—Depicteddecreasesintemperaturebaseduponchanged
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A Brief Solution to Global Warming Using Geoengineering
Global warming is a world problem that requires global participation to remedy the
problems associated with climate change. Policymakers and governments, especially those in
developed nations, still need to lead by example by being the first in reducing GHG emissions by
mitigation. Human adaptation to climate change is also necessary for the earth’s climate is never
consistent and will eventually change no matter what is done with GHG emission regulation.
Still with hopeful heavy future regulation and major impetus in reducing of GHG emissions, the
planet will still warm based upon delayed response of heating from GHG.24 For this reason and
for the uncertain future of GHG emission regulation by governments, currently geoengineering
technology developed by scientists and engineers are the only options to help deal with global
warming head on. Of the two technologies, artificial trees would be the best technology to invest
in globally because it would remove the problem of CO2 in the atmosphere. Wind-driven vessels
would simply “put a bandage” on the problem of CO2 absorption by the emissivity of GHG and
could actually increase GHG emissions by this false impression global warming has been fixed.22
In closing, geoengineering is still a developing technology that requires many minds and
ideas by individuals’ worldwide for its potential development. Hopefully, this relatively new
technology of artificial trees and carbon sequestering along with continued research in wind
driven water vessels and other technologies (reforesting, reflective surfacing, space mirrors) will
hopefully curb anthropogenic climate change if policy fails.
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KlausLackner” .http://thebreakthrough.org/blog/2008/03/from_synthetic_trees_to_carbon.shtml
4Glikson,A.(2009)“Towardclimategeoegineering?|‐FoundedandInspiredbyMargoKingston ”
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Magazine.http://www.popularmechanics.com/science/environment/4256184
7Irvine,PandRidgwell,A.(2009).”Geoengineering—Takingcontrolofourplanet’sclimate ”.TheJournalof
ScienceProgress.Ed.92,pgs139‐162.
8IntergovernmentalPanelonClimateChange(IPCC).WorkgroupI.IPCC(2007).ClimateChange2007:The
PhysicalScienceBasis:ContributionofWorkingGroupItotheFourthAssessmentReportofthe
IntergovernmentalPanelonClimateChange.(S.Solomon,D.Qin,M.Manning,Z.Chen,M.Marquis,K.B.Averyt,
etal.,Eds.)Cambridge,UnitedKingdomandNewYork,NYUSA:CambridgePress.
9Fox,T.etal.,(2009).“GeoengineeringGivingusthetimetoact? ”TheInstitutionofMechanicalEngineers.http://www.imeche.org/Libraries/Key_Themes/IMechEGeoengineeringReport.sflb.ashx .
10EarthSystemResearchLaboratoryWebsite.(2011).“TrendsinCO2”.US.DeptofCommerce—National
Oceanic&AtmosphericAdministration.http://www.esrl.noaa.gov/gmd/ccgg/trends/global.html. 11Fournier,J.(2010).“OceanCollapse—TheRiskofOceanDeathfromCO2 ”.Planetwork.net.
http://www.planetwork.net/oceanacidity/ocean_collapse.html.
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18Mohr,PeterJ.;Taylor,BarryN.;Newell,DavidB.(2008)."CODATARecommendedValuesoftheFundamental
PhysicalConstants: 2006".Rev.Mod.Phys.80:633–730.
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NationalCenterforAtmosphericResearch.http://www.ucar.edu/communications/staffnotes/0405/latham.html
20SalterS.,SortinoG.,LathamJ.(2008).“Sea‐goinghardwareforthecloudalbedomethodofreversingglobal
warming”.JournalofPhilosophicalTransactionsAMath.Phys.Eng.Sci.November13,2008
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maritimeclouds”.Phil.Trans.R.Soc.A‐Math.Phys.Engng.Sci.,366(1882),3969‐3987
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stratocumuluscloud.”InternationalClimatechangeConfrence,HongKong,China,May2007.http://www.mmm.ucar.edu/people/latham/files/cloud_albedo_spray_quantity_paper.pdf
24NationalInstituteofWaterandAtmosphericResearch(2008).“Havegreenhousegasemissionscaused
globaltemperaturestorise ?”http://www.niwa.co.nz/our‐science/climate/common‐questions/all/have‐
greenhouse‐gas‐emissions‐caused‐global‐temperatures‐to‐rise