Winston Churchill once said of the Americans, that we can be counted
on to do the right thing, after we've exhausted all the alternatives.
What are the alternatives to actually cutting our Co2 emissions?
Generally, they're called geoengineering,
based on the idea that we are now powerful
enough that we can actually engineer the planet in some ways.
There are different strategies that are all called geoengineering.
They're very different,
and have possibilities to actually work.
One way that would work
to solve the climate problem, and is my hope
for the future, is to actually eventually
scrub CO2 from the atmosphere. This could be done.
CO2 reacts with a base to make bicarbonate. You saw this
using carbonate ion a base in the seawater chemistry,
this is the buffer mechanism whereby seawater can hold
more CO2 than it would if it didn't have that chemistry.
It can be used in an industrial way, too;
the base that they usually talk
about is called an amine. But it functions in the same way.
You run the CO2 through a solution of this, and it turns into bicarbonate,
and then you have to get the CO2 back off again,
and do something with it. This is how they scrub
CO2 from the air in submarines,
and it's also how they scrub sulfur dioxide
from coal power plants. It's not a novel process.
Once you've captured the CO2 then you have to figure out what to do with it.
The name they use for this is CO2 sequestration.
There are two basic options: on land and in the ocean.
On land, there are deposits, like layers of sandstone,
with coarse enough grains that fluid in between
can flow around, and
deep enough that the water is salty.
They call these saline aquifers.
Since the water is salty, nobody wants it,
might as well put some CO2 in it. It turns out that there is capacity for
thousands of gigatons of carbon in these sorts of deposits in the earth.
They're not evenly spread out around the earth.
We have lots of them in the United States.
There are no such deposits in Japan, for example.
The CO2 at this pressure is actually a liquid, rather than a gas,
and it eventually reacts with the CaO compoenen
of rocks that are down there.
That's the Urey reaction again.
We pump the CO2 down there and it can
react with igneous rocks, which neutralizes it.
The other option that people talk about is to inject it
in the ocean.
Here is a ship and a pipe and a bubbler and you bubble some CO2 out and
and it floats up, it would be liquid in that case, but it would float.
well, it actually depends on the depth in the ocean.
At some depth, the CO2 is more
compressible than water, so it would actually sink.
But either way, it would eventually dissolve in the water.
And once that happens,
the CO2 dissolving in the deep ocean, it
would exchange with the atmosphere, on a time scale
of about 1000 years, just the same as if we had put it in the atmosphere.
It would take 1000 years to equilibrate with the ocean, then you'd add this long tail.
You put it in the ocean, it would
take 1000 years to equilibrate with the atmosphere.
This process would eliminate the peak,
but it wouldn't eliminate the long tail.
It would only be a partial solution to what to do with the CO2.
Another idea that you hear about, which I am personally not a believer in, is to
fertilize the ocean. It is found that in
large sections of the surface ocean, phytoplankton growth
is limited by needing trace amounts of iron, Fe.
There are those who propose putting
iron in the ocean, making the phytoplankton grow.
These dead phytoplankton will sink in the ocean,
pull CO2 out of the surface ocean water.
This is a very strong lever because, you only
need one atom of iron for maybe 20,000 atoms of CO2.
It seems like a very powerful technique.
The problem is that the CO2
in the atmosphere only exchanges with that from the
ocean in, like we've said, about a thousand years.
If you could fertilize the ocean for
a thousand years, you would start to get somewhere.
But in simulations of what happens if you just fertilize
in one spot in the ocean, for a few decades, it's found that the impact on
the CO2 in the atmosphere is very small.
In fact, if you put iron in one spot in
the ocean models, you stimulate lots of production in that spot,
although there are other nutrients like nitrogen and phosphorous
in sea water that limit how much phytoplankton can grow,
So by making one spot in a model that's very productive, you make a
doughnut of areas around it that are less productive,
and so it compensates.
The impact on atmospheric CO2, according to the models, is low.
And if it were actually done you wouldn't really be able to measure how much you're
changing the CO2 concentration of the atmosphere.
If you're looking to buy carbon offsets,
the right to emit carbon by investing some money,
and someone wants to sell you carbon offsets by grinding up old cars and
putting them in the ocean, I would advise you to put your money elsewhere.