New Scientist  [Printer-friendly version]
August 13, 2008

A TANK OF THE GREEN STUFF

By David Strahan

If you have become addicted to the fly-cheap philosophy espoused by
budget airlines over the last decade, it could be time to rethink your
travel plans. Airlines now find themselves facing a crude oil price
that has doubled to more than $140 a barrel in just 12 months, pushing
fuel costs to record levels. Around 10 small carriers have already
gone under, and the industry as a whole is expected to lose $40
billion this year. Airlines are being forced to slash capacity and
merge, and the knock-on effects for passengers are obvious: "Our
customers must ultimately compensate us for the costs we incur flying
them around," warned Gerard Arpey, chairman of American Airlines, at
an airline industry conference in June. With analysts predicting a
further leap to $200 a barrel by 2010, there is no relief in sight.

Yet as bad as things look, the soaring cost of oil is not the biggest
problem the industry and its passengers face. More fundamental is the
need to replace kerosene with another source of energy altogether, for
two pressing reasons.

First, the airline industry is turning out to be the cuckoo in the
nest of carbon reduction. The UK, for instance, is now legally bound
to cut carbon dioxide emissions by 60 per cent to 65 million tonnes a
year by 2050, but under the government's "best case" projection, the
country's aviation industry alone will emit 15.7 million tonnes that
year, almost a quarter of the economy's entire carbon ration.

According to experts at the Tyndall Centre for Climate Change near
Norwich, UK, if additional indirect impacts of aviation -- such as the
effect of contrails -- are taken into account, that figure could rise
to over 100 per cent. Neither scenario is sustainable.

Second, aviation is uniquely vulnerable to the consequences of peak
oil -- the point at which global oil production begins its inevitable
decline. Whereas land-based transport could in theory be completely
electrified, powered by batteries charged from renewable sources,
there is no alternative to energy-dense liquid fuels for jet engines.

There is a growing consensus that global oil production will peak in
the next decade or so and then go into terminal decline. Some analysts
believe it already has: output has been essentially flat since 2005
despite soaring demand, which is why the price is heading skyward.

Even the traditionally optimistic International Energy Agency now
foresees an oil "supply crunch" from 2012. For airlines the problem
could soon be not just whether they can afford jet fuel, but whether
there is enough of it to go round.

If airlines are to have any chance of staying aloft in a post-peak,
carbon-rationed world, they must quickly find an alternative fuel with
low emissions that also matches the stiff technical standards of jet
kerosene. Because planes have to lift their fuel into the sky and
carry it for the entire journey, this fuel has to be energy dense.

Because they fly at high altitude, it needs to remain fluid at -50
deg. C.

Because they fly long distances, chemically identical supplies must be
available all over the world. And because airliners have long lives,
the new fuel must be compatible with the existing fleet. What's
needed, in other words, is an exact replica of old-fashioned jet
kerosene -- a so-called "drop-in" replacement -- that also emits
substantially less CO2 per unit of energy. "Meeting all these
conflicting demands is a very tall order," says Mike Farmery, global
fuel technical and quality manager at Shell Aviation. "There are lots
of exciting ideas, but it will be hard to achieve quickly." So what
are our alternatives?

Veggie powerUntil recently it was widely thought that using biofuels
like bioethanol or biodiesel in aviation was a non-starter. Scientists
have known since the 1940s how to turn vegetable oil into biodiesel
using a process called transesterification, in which the oil is
processed using alcohol and an acid catalyst. This produces fuels that
work well on the ground but not at altitude: the natural freezing
point of such oils is too high, so they would congeal at 33,000 feet.

They also contain too much oxygen, which adds weight but not energy
content.

However, it now seems those technical problems have been cracked.

Finnish oil company Neste has devised a way to produce an oxygen-free
biodiesel called NExBTL, which could in theory be used to make jet
fuel. Neste already has two plants manufacturing NExBTL and has
another two in the pipeline.

Meanwhile in February 2008, airline Virgin Atlantic conducted a test
flight using a biofuel made from coconut and babassu oil produced by
Imperium Renewables, a Seattle-based company that has developed a
patented method of reducing the freezing point. A second test flight
with an Air New Zealand plane is planned later this year.

The problem with so-called first-generation biofuels -- made using
conventional fermentation and distillation procedures from wheat, say
- remains the amount of feedstock and land required. During Virgin's
test flight from London to Amsterdam, the Boeing 747 consumed 22
tonnes of fuel, of which only 5 per cent was neat biofuel. Producing
even that much required the equivalent of 150,000 coconuts, says Brian
Young, Imperium's director of international business development. Had
this single flight been run entirely on biofuel, it would have
consumed 3 million coconuts -- an astronomical number that highlights
the scale of the problem. However, Virgin and its partners Boeing and
GE stressed that the flight was simply a "proof of concept", and
accepted that producing useful amounts of fuel would require "next
generation" feedstocks: those made from non-food crops, waste biomass
or by converting existing fuels to liquid form.

One option, which Virgin's Richard Branson suggested at the launch of
his airline's test flight, would be to produce fuel from the nuts of
Jatropha curcas. This hardy bush grows in the tropics on relatively
poor land with little water or fertiliser, so it needn't displace food
production. However, the amount of land required to fuel the world's
jet planes would still be prodigious (see map).

Aviation currently consumes around 5 million barrels of jet fuel per
day, or 238 million tonnes per year. On current Jatropha yields -- 1.7
tonnes of oil per hectare -- replacing that would take 1.4 million
square kilometres, well over twice the size of France. To put this in
context, D1 Oils, the British company pioneering biofuel from Jatropha
in countries such as India, Zambia and Indonesia, plans to plant
10,000 km2 over the next four years.

If vegetable oil looks likely to remain in short supply, another
approach would be to make jet fuel from plant material using the
Fischer-Tropsch chemical process developed in Germany in the 1920s.

Originally designed to produce synthetic diesel from coal, the
Fischer-Tropsch process also works with a wide range of organic
matter. The feedstock is heated without oxygen to create a synthetic
gas that is then converted to high-quality liquid fuels using high
temperatures and iron-based catalysts. This makes it possible to
create a synthetic jet fuel that is indistinguishable from
conventional kerosene. Depending on the feedstock, the fuel could in
principle have very low carbon emissions and not compete with food
production. Unfortunately, though, all the feedstocks have significant
drawbacks.

For example, Fischer-Tropsch jet fuel is already produced from coal by
Sasol in South Africa, and planes refuelling in Johannesburg get a
half-and-half blend of kerosene and coal-to-liquids (CTL) fuel. The
problem with CTL is that life-cycle emissions are roughly double those
of kerosene, making CTL-powered aviation even more damaging to the
climate.

The Fischer-Tropsch process also works with natural gas. Gas-to-
liquids (GTL) jet fuel was tested by Airbus and Shell earlier this
year. Well-to-wing emissions are lower than CTL, yet no better than
conventional kerosene, because the Fischer Tropsch process itself
consumes so much energy. According to Airbus's rival Boeing, GTL jet
fuel emits 1.5 times as much CO2 as kerosene.

The only realistic hope of producing Fischer-Tropsch jet fuel with
substantially lower emissions is to use some form of plant material
such as wood or straw as the feedstock -- so-called biomass-to-
liquids, or BTL -- as championed by the German company Choren, which
plans to start full-scale production by 2012. The company boldly
proclaims a vision of "potentially infinite production of renewable
energy", but a closer look at the numbers suggests the real outlook
will be more modest.

In a presentation at the World Future Energy Summit in Abu Dhabi in
January, Choren CEO Tom Blades said the company's BTL fuel could
reduce greenhouse gas emissions by up to 91 per cent, and insisted it
would not compete with food production. One reason for this is that a
large proportion of the feedstock will come from waste construction
timber and existing forestry -- initially. However, Blades
acknowledged that further BTL expansion would require increasing
amounts of specially grown "energy crops" such as willow or
miscanthus. Supplies of waste timber aren't expected to grow, so
within 10 years, more than half of Choren's feedstock will need to
come from energy crops, again raising the issue of land use.

Food not fuelBlades cites the EU's Biomass Action Plan report of
December 2005, which suggests that Europe has the potential to produce
around 100 million tonnes of energy crops annually by 2030, and that
total available biomass, including waste and forestry contributions,
could amount to 315 million tonnes. Since Choren's BTL process takes 5
tonnes of dry biomass to produce a tonne of fuel, this would produce
just over 60 million tonnes of fuel per year. That sounds a lot until
you remember that in 2006 the EU consumed more than 700 million tonnes
of crude. "We're not replacing oil," Blades admits, "just making it
last a little bit longer."

In the context of global aviation, the numbers are even more daunting.

Meeting today's global demand for jet fuel from BTL would require -
assuming the average crop yields 10 tonnes of biomass per hectare -
nearly 1.2 million km2. That's well over three times the size of
Germany, and makes no allowance for the predicted rapid growth in
aviation. On the same assumptions, replacing all current transport
fuel with BTL would require more than 10 million km2 -- an area bigger
than China. This demolishes any claim that second-generation biofuels
wouldn't have to compete with food production.

The one remaining alternative for low-emission jet fuel that doesn't
compete with agriculture are algae, which can be grown in ponds of
seawater built on non-productive land. Given the right conditions,
some species multiply quickly and produce oil, which can then be
extracted and refined. It is widely agreed that such a system could
take up less space and deliver much higher yields than oil crops such
as palm or Jatropha -- although quite how much higher is still
controversial.

"Algae could deliver much higher yields than oil crops, though how
much higher is still controversial"The technology itself is not new.

Ami Ben-Amotz, a senior scientist at Israel's National Institute of
Oceanography in Haifa, has been farming algae commercially for more
than 20 years to produce beta-carotene food supplements for the
Japanese market. In 2004 he founded a new company, Seambiotic, to
produce algae for biofuel at a coal-fired power station on the coast
at Ashkelon.

It is an undeniably neat arrangement. Warm water from the power
station's cooling system is diverted through the ponds before
returning to the sea. Meanwhile flue gas from the station's chimney
supplies CO2 to feed the algae, and energy for pumping and harvesting
is available at minimal cost. The harvested algae are then reduced to
a concentrated paste and mixed with solvents to separate the oil,
which can be turned into biofuel by transesterification. Seambiotic is
delighted with the results and aims to complete a larger, 50,000-
square-metre pond on the site by the end of the year. Ben-Amotz says
that refineries could offer similar opportunities.

Algae have stirred up huge excitement, not only because they have the
potential to help mop up CO2 emissions, but also because of the sheer
amount of fuel they might produce. Shell, which is building a pilot
facility in Hawaii, claims algae could be 15 times as productive as
traditional biofuel crops. Boeing believes algae could produce 85 to
170 tonnes per hectare per year (10,000 to 20,000 US gallons per acre
per year), yielding all the world's jet fuel in an area the size of
Belgium. Yet the scientists who have done most research into algae
production look askance at such claims.

The fundamental problem, explains Al Darzins, who coordinates alga
research at the US National Renewable Energy Laboratory in Golden,
Colorado, is that although algae grow very quickly, most of their
biomass is usually carbohydrate. To trigger a higher proportion of
oil, you have to stress the algae in some way -- starve them of
nutrients such as nitrogen, say -- which in turn limits their growth
rate. As a result, Darzins thinks 42 tonnes per hectare is a more
realistic target.

Ben-Amotz is even more cautious. To grow algae cheaply means using
open ponds, which are prone to invasion by local alga species that do
not produce oil, or by predatory micro-organisms. There are also the
day-to-day problems of keeping temperature and salinity constant, so
theoretical levels of productivity are hard to maintain on large
scales and over the long term. "If people say it's possible, let them
show me," Ben-Amotz says. "But usually they only show me a bucketful."

With over 20 years' production experience, Ben-Amotz is convinced that
the maximum practical yield is 25 grams of biomass per square metre
per day, of which 40 per cent might be oil. That equates to about 36
tonnes per hectare per year, meaning that to replace current jet fuel
consumption would take about 65,000 km2, roughly the area of Ireland.

Massively better than BTL, but still enormous.

Nevertheless there is intense interest in algal jet fuel in both civil
and military aviation -- hardly surprising, since jet fuel eats almost
60 per cent of the US Department of Defense's annual fuel bill,
burning up over $6 billion in 2006. America's Defense Advanced
Research Projects Agency (DARPA) is sponsoring research into ways to
produce JP-8 military jet fuel from crop oils, including algae. The
target is to produce a fuel that achieves at least 60 per cent
conversion efficiency from the crop oil to jet fuel, eventually rising
to 90 per cent, all for less than $3 per gallon. Three contractors
will deliver fuel samples this autumn, and DARPA is assessing
proposals for further research.

Algal jet fuel also has its fans in civil aviation, including Virgin
and Boeing, which is no surprise since it seems to offer the best bet
in a gamble where the stakes are literally sky-high: nothing less than
the survival of aviation as we know it. However, the main concern may
not be space so much as time. At the launch of the Virgin biofuel test
flight, Branson suggested that algae might produce enough fuel for the
entire airline industry, and that such technological breakthroughs
represented the only chance of mitigating peak oil, which he said
could arrive within six years. But when asked if fuels like Jatropha
or algae could be ready by then, he did not sound so confident: "We
have to try our best to make them available as fast as we possibly
can."

Copyright Reed Business Information Ltd.