Econ_June_09

The Economist

June 9th 2018

Science and technology 69

diabetic retinopathy and age-related mac-

ular degeneration. The firm is alsoworking

onmammography.

Heart disease is yet another field of in-

terest. Researchers at Oxford University

have been developing

s intended to in-

terpret echocardiograms, which are ultra-

sonic scans of the heart. Cardiologists

looking at these scans are searching for

signs of heart disease, but can miss them

20% of the time. That means patients will

be sent home andmay then go on tohave a

heart attack. The

, however, can detect

changes invisible to the eye and improve

the accuracyofdiagnosis. Ultromics, a firm

in Oxford, is trying to commercialise the

technology and it could be rolled out later

this year in Britain.

There are also efforts to detect cardiac

arrhythmias, particularlyatrial fibrillation,

which increase the risk of heart failure and

strokes. Researchers at StanfordUniversity,

led by Andrew Ng, have shown that

software can identify arrhythmias froman

electrocardiogram (

ECG

) better than an ex-

pert. The group has joined forces with a

firm that makes portable

ECG

devices and

is helping Apple with a study looking at

whether arrhythmias can be detected in

the heart-rate data picked up by its smart

watches. Meanwhile, in Paris, a firm called

Cardiologs is also trying to design an

in-

tended to read

ECG

Seeing ahead

Eric Topol, a cardiologist and digital-medi-

cine researcher at the Scripps Research In-

stitute, in San Diego, says that doctors and

algorithms are comparable in accuracy in

some areas, but computers have the ad-

vantage of speed. This combination of

traits, he reckons, will lead to higher accu-

racy and productivity in health care.

Artificial intelligence might also make

medicine more specific, by being able to

draw distinctions that elude human ob-

servers. It may be able to grade cancers or

instances of cardiac disease according to

their risks—thus, for example, distinguish-

ing those prostate cancers that will kill

quickly, and therefore need treatment,

from those that will not, and can probably

be left untreated.

What medical

will not do—at least

not for a long time—ismake human experts

redundant in the fields it invades. Mach-

ine-learning systems work on a narrow

range of tasks and will need close supervi-

sion for years to come. Theyare “blackbox-

es”, in that doctors do not know exactly

how they reach their decisions. And they

are inclined to become biased if insuffi-

cient care is paid to what they are learning

from. They will, though, take much of the

drudgery and error out of diagnosis. And

theywill also helpmake sure that patients,

whether being screened for cancer or taken

from the scene of a car accident, are treated

in time to be saved.

N MAY some 250 scientists and policy

types from around the world convened

in Gothenburg, Sweden, to discuss a dirty

secret of the three-year-old Paris climate

agreement. Virtuallyall simulationswhich

chart paths towardmeeting that compact’s

goal—to keep temperature rise “well be-

low” 2°C relative to pre-industrial levels—

assume not just a sharp reduction in actual

emissions but also the removal of carbon

dioxide from the atmosphere on amassive

scale. One reason such “negative emis-

sions” have been absent from climate dis-

cussions—the Swedish shindig being the

first of its kind—is that no one has a good

idea of how exactly to bring them about.

The obvious solution is to plant lots of

trees, to convert CO

into wood. But this

would mean foresting an area with a size

somewhere between that of India and

Canada. Alternative, engineered fixes

have been dogged by potentially strato-

spheric costs, uncertain efficacy or both.

No longer, reckons David Keith. Besides

his day job as a climate expert at Harvard

university, Dr Keith is a co-founder of Car-

bon Engineering, a nine-year-old firm that

counts Bill Gates among its backers. Dr

Keith and his colleagues argue in a paper

they have just published in

Joule

that the

-removal technique they have been

perfecting is no pipe dream—even if it does

contain pipes aplenty.

Their process has four steps. First, air is

channelled by fans onto a honeycombed

plastic slab called a contactor, where CO

which is acidic, reacts with aqueous potas-

sium hydroxide, which is alkaline. The re-

sulting solution of potassium carbonate is

filtered and exposed to a slurry of calcium

hydroxide. This produces potassium hy-

droxide, which is recycled back to the con-

tactor, and pellets of calcium carbonate.

These are whisked to the third receptacle,

calleda calciner. There the calciumcarbon-

ate is heated to 900°C to release pure car-

bon-dioxide gas ready for capture, and cal-

cium oxide. Finally, the calcium oxide is

piped to a “slaker”, where it is dissolved in

water to form calcium hydroxide, which is

reused in the second step.

If that all sounds complicated, chemi-

cally speaking it is not. Nor is the idea new.

A researcher called Klaus Lackner came up

with the principles 20 years ago and Dr

Keith patented his version in 2015. A pilot

plant with a contactor three by five metres

across and threemetres deephas been run-

ning for three years. It extracts a tonne of

carbon dioxide from the air per day.

What sets Dr Keith’s latest paper apart

from his earlier publications—and, indeed,

those of other putative carbon-hoovers—is

that it offers a hard-nosed estimate of the

system’s cost and scalability. The results

lookencouraging.

That is principally because each step in

Dr Keith’s scheme is adapted from known

industrial processes. The contactor was

pinched from factory cooling towers. The

pellet reactor came from water-treatment

plants. The calciner was developed from

metal-ore purification apparatus. And the

slakerwas adapted frompulpmills. The re-

quired tweaks were small enough to per-

mit Carbon Engineering to procure the

paraphernalia for the prototype plant from

existing suppliers. Crucially, this also en-

abled the suppliers—and an independent

engineering consultancy hired by Carbon

Engineering—to estimate how much it

would cost to build a fully fledged facility

(envisaged in the picture above) capable of

extractingbetween100,000 and1mtonnes

Climate change

The power of negative thinking

Extracting carbon dioxide fromthe atmosphere is possible. But atwhat cost?