The EconomistDecember 7th 2019 BriefingNegative emissions 252
1But the biggest problem with using new
or restored forests as carbon stores is how
big they have to be to make a serious differ-
ence. The area covered by new or restored
forests in some of the ipccscenarios was
the size of Russia. And even such a heroic
Johnny Appleseeding would only absorb
on the order of 200bn tonnes of CO 2 ; less
than many consider necessary.
The sort of bioenergy with carbon cap-
ture and storage (beccs) power station that
Drax wants to turn itself into would allow
more carbon to be captured on the same
amount of land. The trick is to use the bio-
mass not as a simple standing store of car-
bon, but as a renewable fuel.A question of combustion
The original use envisaged for carbon cap-
ture and storage (ccs) technology was to
take CO 2 out of the chimneys of coal-fired
power plants and pump it deep under-
ground; do it right and the power station
will be close to carbon-neutral. Apply the
same technology to a biomass-burning
plant and the CO 2 you pump into the depths
is not from ancient fossils, but from re-
cently living plants—and, before them, the
atmosphere. Hey presto: negative emis-
sions. And beccsdoes not just get rid of
CO 2 : it produces power, too. The solar ener-
gy that photosynthesis stored away in the
plants’ leaves and wood gets turned into
electricity when that biomass is burned. It
is almost as if nature were paying to get rid
of the stuff.
There are, as you might expect, some
difficulties. Even if you regularly take some
away for burning, growing biomass on the
requisite scale still takes a lot of land. Also,
the bog-standard ccsof which beccs is
meant to be a clever variant has never really
made its mark. It has been talked about for
decades; the ipccproduced a report about
it in 2005. Some hoped that it might be-
come a mainstay of carbon-free energy
production. But for various reasons, tech-
nical, economic and ideological, it has not.
The world has about 2,500 coal-fired
power stations, and thousands more gas-
fired stations, steel plants, cement works
and other installations that produce indus-
trial amounts of CO 2. Just 19 of them offer
some level of ccs, according to the Global
Carbon Capture and Storage Institute
(gccsi), a ccs advocacy group. All told,
roughly 40m tonnes of CO 2 are being cap-
tured from industrial sources every year—
around 0.1% of emissions.
Why so little? There are no fundamental
technological hurdles; but the heavy in-
dustrial kit needed to do ccsat scale costs a
lot. If CO 2 emitters had to pay for the privi-
lege of emitting to the tune, say, of $100 a
tonne, there would be a lot more interest in
the technology, which would bring down
its cost. In the absence of such a price, there
are very few incentives or penalties to en-courage such investment. The greens who
lobby for action on the climate do not, for
the most part, want to support ccs. They
see it as a way for fossil-fuel companies to
seem to be part of the solution while stay-
ing in business, a prospect they hate. Elec-
tricity generators have seen the remarkable
drop in the price of wind and solar and in-
vested accordingly.
Thus Drax’s ccsfacility remains, at the
moment, a pair of grey shipping containers
sitting in a fenced-off area outside the
main boiler hall, dwarfed by the vast build-
ings and pipes that surround them. Inside
the first container, the flue gases—which
are about 10% CO 2 by volume—are run
through a solvent which binds avidly to
CO 2 molecules. The carbon-laden solvent is
then pumped into the second container,
where it is heated—which causes it to give
up its burden, now a pure gas.
This test rig produces just one tonne of
CO 2 a day. The pipe through which the flue
gases enter it is perhaps 30cm across. High
above it is another pipe, now unused,
which in coal-burning days took all the flue
gases to a system that would strip sulphur
from them. It is big enough that you could
drive down it in a double-decker bus with
another double-decker on top. That is the
pipe that Drax would like to be able to in-
vest in using.
In some circumstances, you do not
need a subsidy, a carbon price or any other
intervention to make capturing CO 2 pay.
Selling it will suffice. The commercial useof CO 2 is nothing new. Not long after the
great British chemist Joseph Priestley first
made what he called “fixed air” in the 1760s,
an ingenious businessman called Johann
Jacob Schweppe was selling soda water in
Geneva. CO 2 , mostly from natural sources,
is still used to make drinks fizzy and for
other things. Many greenhouses make use
of it to stimulate the growth of plants.The use case
The problem with most of these markets
from a negative-emissions point of view is
that the CO 2 gets back into the atmosphere
in not much more time than it takes a
drinker to belch. But there is one notable
exception. For half a century oil companies
have been squirting CO 2 down some of
their wells in order to chase recalcitrant oil
out of the nooks and crannies in the
rock—a process known as enhanced oil re-
covery, or eor. And though the oil comes
out, a lot of the CO 2 stays underground.
The oil industry goes to some inconve-
nience to capture the 28m tonnes of CO 2 a
year it uses for eorfrom natural sources
(some gas wells have a lot of CO 2 mixed in
with the good stuff ). That effort is reward-
ed, according to the International Energy
Agency, with some 500,000 barrels of oil a
day, or 0.6% of global production. That
seems like a market that ccscould grow
into—though the irony of using CO 2 pro-
duced by burning fossil fuels to chase yet
more fossil fuels out of the ground is not
lost on anyone.Do the carbon shuffle
Carbon flows between atmosphere, biosphere and solid earthSources: Nature; The EconomistBioenergy with CCS (provides energy)
Carbon drawn from the atmosphere into the
biosphere is stored back in the solid earthBiosphereAtmosphereSolid earthDirect air capture (requires energy)
Carbon from the atmosphere is
stored in the solid earthBiosphereAtmosphereSolid earthBioenergy (provides energy)
Carbon from biomass is emitted back into the
atmosphere whence it recently cameBiosphereAtmosphereSolid earthCarbon capture & storage (CCS) (can provide energy)
Carbon from fossil fuels is stored back
in the solid earthBiosphereAtmosphereSolid earthGrowing forests and improving farms (neutral)
Carbon from the atmosphere is stored in the biosphereBiosphereAtmosphereSolid earthFossil-fuel burning (provides energy)
Carbon from fossil fuels is emitted into the atmosphereBiosphereAtmosphereSolid earth