快猫短视频

IF FORESTS are not sucking up enough carbon dioxide to halt global warming,
why not make an artificial 鈥渟uperforest鈥� instead? A team of US government
researchers estimate that a superforest which covers 200,000 square
kilometres鈥攔oughly the size of Minnesota鈥攚ould absorb CO₂
as fast as humanity is now churning it out.

Most strategies to curb global warming focus on producing less CO₂.
But Hans Ziock of Los Alamos National Laboratory in New Mexico argues that we
need to concentrate more on removing CO₂ with 鈥渟crubbers鈥�.

Carbon dioxide scrubbers were first suggested as a way of reducing emissions
from individual power plants and even vehicles. But installing them would be a
huge burden on existing industries. Now Ziock and colleagues Klaus Lackner and
Scott Eliott say you don鈥檛 actually have to build the scrubbers where the CO
₂ is produced.

Lackner studied a simple reaction in which a calcium hydroxide solution
absorbs dilute CO₂ from the air. You can then recover the solid calcium
carbonate from the scrubber and heat it to extract the CO₂. The calcium
oxide residue is recycled back into the solution and the pure CO₂ is
reacted with naturally occurring magnesium silicates to form a stable rock-like
solid that鈥檚 easy to dispose of.

Ziock realised that the wind would play a crucial role. 鈥淥nce every week the
wind goes all the way round the Earth, so one can process a large fraction of
the atmosphere over the course of a few years.鈥� In the lab, the researchers
tested how much CO₂ would be absorbed by a static scrubber with typical
winds flowing over it.

Based on this data, they estimate that a huge scrubber, essentially a
collection of calcium hydroxide ponds with an area of 200,000 square kilometres
would remove about 7 gigatonnes of CO₂ per year鈥攅qual to the
amount people produce.

The team also calculated that the forest could be a fraction of that size if
you draw up more solution and expose more of it to the air using vertical fences
with branching features, like windmills or trees. Such structures would be able
to absorb 20 to 30 times as much CO₂as a regular forest.

Other researchers say the idea compares favourably with other ways of
reducing emissions, such as converting electricity production to wind or solar
power. 鈥淚鈥檓 really happy to see some new and clever thinking,鈥� says Jae Edmonds
of Pacific Northwest National Laboratory鈥檚 office in Washington DC. The cost is
a worry, says F. Sherwood Rowland of the University of California at Irvine, but
鈥渢he longer the population keeps releasing CO₂ directly to the
atmosphere, the more likely the answer will require driving levels back down.鈥�