The road to sustainability
“Sustainability” is the hottest topic in energy research today, but what does it actually mean?
George Crabtree and John Sarrao describe what makes a technology sustainable, and outline the
materials-science challenges standing between us and clean, long-lasting energy
George Crabtree is a
Distinguished Fellow
in the Materials
Science Division of
the Argonne National
Laboratory,
e-mail crabtree@
anl.gov. John Sarrao
is a physicist and
Program Director for
the Office of Science
Programs at the
Los Alamos National
Laboratory, e-mail
sarrao@lanl.gov
The oil shock of the 1970s triggered worldwide awareness of oil dependency and launched a search for alternative sources of energy. But three decades on, these
efforts have barely had an impact: oil still accounts for
almost 40% of global energy use, and fossil fuels make
up 85%. The US, for example, imported 20% of its oil
in 1970; today the figure is 60%, and other countries
import even larger fractions of the oil they consume.
The problem of oil dependency is compounded by cost.
Before the current recession, the price of oil peaked at
$140 a barrel – five times its price in 2002 and 10 times
its price in 1976 – rewriting the economics of transportation, food, manufacturing and trade that underlie
the operation of society. In addition to dependency and
cost, energy security is a pervasive threat. The concentration of oil production in a few regions of the world
makes the supply of oil vulnerable to unpredictable
events such as weather, terrorism, and geopolitical
manoeuvring. Because oil provides so much of our energy, severe reductions in its flow would dramatically
change the way we live.
The current outlook for energy adds a crucial new
dimension that was not present in the first oil shock:
carbon-dioxide emissions and climate change. The
Intergovernmental Panel on Climate Change has documented global warming through rising sea levels,
shrinking snow cover in the northern hemisphere and
higher surface temperatures. These increases in temperature track similar increases in the concentration
of carbon dioxide in the atmosphere – a remarkable
correlation that extends over four ice ages covering the
last 400 000 years. Carbon-dioxide levels are now 30%
higher than they were before the Industrial Revolution,
and they are rising at an accelerating pace, driven by
the human combustion of fossil fuels. The potential
implications for global warming and climate change
are sobering. Left unchecked, climate change could
produce dislocations in the agricultural, trade and
demographic patterns that define global economic and
social structures.
A particularly worrying feature of global warming is
the timescale involved. It takes 400–1000 years for carbon dioxide in the atmosphere to equilibrate in the
deep ocean. Hence, the carbon dioxide that we have
already added – and continue to add – to the atmosphere will affect not only our grandchildren but also
their grandchildren and many generations beyond. The
long-term impact of global warming requires a sustained investment of intellectual resources to understand the dynamics of climate change, rather than the
short-lived interest and spending surge that followed
the oil shock of the 1970s.
The dual challenges of energy and climate are captured in a single term: sustainability. Our current reliance on oil and other fossil fuels (see figure on page
26) and our unfettered emission of carbon dioxide to
the atmosphere are not sustainable activities. We are
using oil and fossil fuels at far greater rates than nature
creates them, and their cost and supply are fragile and
volatile. Our carbon-dioxide emissions are growing by
22% per decade and they threaten to overwhelm the
ability of the ocean–atmosphere system to absorb them
and maintain a stable climate. These activities not only
deplete the fossil resources required for our current
