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CARBON DIOXIDE-STORE-SEA
Chinese scientists find carbon dioxide can be stored in deep-sea sediments
WASHINGTON, July 5, 2018 (BSS/Xinhua) – Chinese researchers found that
carbon dioxide can be stored in deep-sea sediments stably and safely.
The study, published on Wednesday in the journal Science Advances,
revealed that the negative buoyancy effect caused by high density of liquid
carbon dioxide, along with the formation of carbon dioxide hydrate, could
provide an effective barrier to prevent the upward flow of the injected
carbon dioxide.
Carbon capture and storage is considered to be a promising option to
stabilize the atmospheric concentration of human-caused carbon dioxide and
mitigate climate change.
Although conventional proposals for geologic sequestration, including
injection into deep saline aquifers, oil and gas fields, and deep coal seams
are prospective, the stored carbon dioxide is so buoyant that it may escape
from permeable pathways into the atmosphere, according to the study.
Carbon sequestration in deep-sea sediments could take advantage of the
high pressure and low temperature of subsea sediments, according to the
study.
The paper’s senior author Zhang Dongxiao, a professor at Peking
Univeristy, told Xinhua, the required infrastructure of this option is
similar to that used in the recent pilot of natural gas hydrate extraction in
the South China Sea.
“Compared with previous studies, the superiority of our study is the
incorporation of the dynamics of dissolved components and their corresponding
effects on hydrate reaction and fluid flow,” said the paper’s first author
Teng Yihua who worked at Zhang’s team.
“This allows us to study the long-term evolution of different phases and
components,” said Teng. “Consequently, we are able to predict the long-term
changes of the injected carbon dioxide, which is not possible in previous
studies.”
According to Teng, if the buoyancy-driven upward flow is too fast, the
injected carbon dioxide may not be sufficiently cooled down, which means that
hydrate may not form even if carbon plume enter the hydrate formation zone in
static condition.
Whether carbon dioxide would escape or be trapped depended on the
interaction of the competing processes of buoyant flow, hydrate formation,
and density increase of carbon dioxide induced by heat loss, Teng said.
The study showed that the low buoyancy and the formation of hydrate could
effectively trap the injected carbon dioxide in a cage-like system and the
injected carbon dioxide would finally dissolve and migrate away through
diffusion in the long term, thus leading to permanent storage.
“We are very excited about the results, because it proves that this option
is long-term viable and certainly would be an alternative of terrestrial
sequestration,” said Teng.
BSS/XINHUA/FI/ 0832 hrs