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| Titel |
Increased chemical weathering of olivine in high-energy shelf seas can counteract human CO2 emissions and ocean acidification against a price well below that of CCS and other methods |
| VerfasserIn |
Poppe L. de Boer, Roelof D. Schuiling |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250100437
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| Publikation (Nr.) |
 EGU/EGU2014-16404.pdf |
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| Zusammenfassung |
| In the reaction: Mg(Fe)2SiO4 (olivine) + 4 H2O 2 Mg(Fe)2+ + 4 OH- + H4SiO4, followed
by 4 OH- + 4 CO2 4 HCO3-, CO2 is consumed, and Mg2+, Fe2+, H4SiO4 and HCO3- are
produced.
Contrary to the paradigm that olivine weathering in nature is a slow process, flume
experiments show a fast reaction, consuming CO2, and raising the pH at short notice. Only
under static conditions a silica coating develops that retards the reaction. In high-energy
shallow marine environments such silica coatings are abraded so that the chemical reaction
can continue. When kept in motion even large olivine grains and gravels, rubbing and
bumping against each other and against other sediment grains, weather quickly. Experiments
show that fine micron- to silt-sized olivine particles are produced, and that the chemical
reaction is fast.
The chemical weathering of 7 km3 olivine is needed on a yearly basis in order to
compensate the human CO2 emissions. This seems much, but is of the same order of
magnitude as the volume of fossil fuels (in oil equivalents ~10 km3) that are burnt annually.
Olivine is readily available at the Earth’ surface on all continents, and such volume
of 7 km3 is exceeded by existing mines; e.g. the Bingham Canyon open pit mine
in Utah has an excavated volume of 25 km3. Hydrocarbons, on the other hand,
are commonly retrieved with great efforts, from great depths, and often at remote
locations.
Spreading of large amounts of olivine (and/or serpentinite) in high-energy shelf seas
where coarse sand and gravel can be transported, will counteract human CO2 production by
fossil fuel burning and ocean acidification against a price well below that of other methods;
order of US$ 10.- per ton CO2.
For example part of the continental shelf between the Shetland Isles and France, that is
the Southern Bight of the North Sea, the English Channel and the Irish Sea, is covered with
sand waves, and in and around the English Channel an area of well over 100,000
km2 experiences bed shear stresses capable of transporting gravel. A volume of
0.35 km3 coarse olivine grains, one cm thick, when applied to an area of 35,000
km2 where gravel can be transported (or a thinner layer over a larger area), would
compensate 5% of a year’s worldwide CO2 emissions. This 5% exceeds the combined
annual CO2 emissions of the adjacent countries, the United Kingdom, France, The
Netherlands, Belgium and Ireland, together responsible for about 4% of the world’s CO2
emissions.
This is a safer and cheaper approach than CCS. Moreover, contrary to CCS, adding
olivine to the marine system in areas where it weathers fast, is an effective way
to counteract ocean acidification. It brings bio-limiting nutrients, Si and Fe, into
the system that will stimulate primary productivity thus trapping even more CO2. |
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