11 Jun 2009

For Greening Aviation, Are Biofuels the Right Stuff?

Biofuels – made from algae and non-food plants – are emerging as a potentially viable alternative to conventional jet fuels. Although big challenges remain, the reductions in greenhouse gas emissions could be major.
By david biello

Earlier this year, a Continental jet accelerated down the runway at George Bush Intercontinental Airport in Houston. Nothing out of the ordinary for Capt. Rich Jankowski, who countless times in his 38-year career had eased such two-engine Boeing 737-800s into the sky. Except on this experimental flight, one of the engines Jankowski relied on was burning fuel derived from microscopic algae to push the 45-ton aircraft into the air and keep it aloft — a first in aviation history.

Last year, Virgin Atlantic flew the first commercial jet on biofuels, a 40-minute jaunt between London and Amsterdam in which one engine burned a mix of 80 percent conventional jet fuel and 20 percent biofuel derived from coconuts and babassu nuts. Other test flights have followed, culminating in a 90-minute Japan Airlines flight with one engine burning a blend of biofuel from camelina — a weedy flower native to Europe — and regular jet fuel at the end of January.

As global economies strive to wean themselves off fossil fuels, one of the most daunting challenges is to find a replacement for the liquid fuels that power the world’s aircraft. Biofuels made from algae and non-food plants are now the leading contenders. While homes, cars, and offices can be powered by electricity produced from such renewable sources as solar, wind, and hydropower, there is little likelihood in the near future that battery power will be lifting a jumbo jet into the sky. And the global aviation industry uses an enormous amount of jet fuel — energy-dense kerosene — frequently referred to as Jet A or JP-8: The U.S. commercial airlines alone burn about 50 million gallons of jet fuel every day, at a cost of roughly $150 million.

That’s a lot of greenhouse gases, released right where they can do the most damage — high in the atmosphere. The warming properties of jet fuel exhaust are intensified at high altitude, where nitrogen oxides from the
The challenge is how to produce enough biofuel to supply even a fraction of the jet fuel burned every year by the world’s aircraft.
jet’s turbines react with other molecules in the upper atmosphere to increase levels of ozone, which traps heat, according to the Intergovernmental Panel on Climate Change. The water vapor that forms contrails and other chemically active gases emitted during flight also contributes to climate change. Although the amount of emissions from aircraft compared with other vehicles is relatively small — roughly 3 percent of total worldwide greenhouse gas emissions from fossil fuel burning — the mix of compounds in jet emissions and their release in the upper troposphere intensifies their heat-trapping power.

The environmental appeal of biofuels — especially if they are produced from algae or other non-food sources — is strong. Preliminary results from an Air New Zealand test flight in December show that burning biofuels — in this case jet fuel refined from jatropha oil — can cut greenhouse gas emissions by at least 60 percent compared to conventional fuel. And, as a bonus, about 1.4 metric tons of fuel could be saved on a 12-hour flight using a biofuel blend.

This month, the International Air Transport Association set a goal of achieving “carbon neutral growth” — meaning an increase in air travel would not emit any more CO2 than the present fleet and flight schedule — by 2020. The keys will be increasing fuel efficiency by 1.5 percent per year and using biofuel blends, according to IATA.

The overwhelming challenge is how to produce enough biofuel to supply even a fraction of the more than 60 billion gallons of jet fuel burned every year by the world’s aircraft. Relying heavily on biofuels made from food
Biofuels Digest
Camelina, a weedy flower native to Europe, is a promising biofuel source. One camelina-jet fuel blend reduces CO2 emissions more than 80 percent.
crops — such as soybeans, sugar cane, or canola — would not only affect food supplies and increase food prices, but would produce significant greenhouse gases during the planting and harvesting of these crops, as well as from forest clearing for more agricultural land. Non-food plant sources, such as jatropha and camelina, are promising, but difficult to produce in large quantities and can end up displacing food crops or lead to deforestation if the price of fuel rises high enough. Finally, making large amounts of jet fuel from algae represents a major hurdle, from perfecting the algae’s growth to extracting the oil cost-effectively.

Nevertheless, industry and government interest is driving research and testing into the development of biofuel-based jet fuels. Boeing has been conducting tests with various plant sources, including camelina. And the U.S. Defense Department’s Defense Advanced Research Projects Agency (DARPA) and the U.S. Air Force are working on the development of alternative fuel sources to free the military from its reliance on fossil fuels.

The bulk of the initial bio-jet fuel for test flights has come from jatropha — a poisonous shrub native to Central America — and camelina. Both plants produce oil-rich seeds. Terasol Energy — a company based in the U.S., India, and Brazil and the supplier of the oil for the Continental flight — can squeeze 242 gallons of jatropha oil per acre of farmland in India and Tanzania.

But jatropha and camelina have their own issues, such as the inevitable competition between crops grown for food and crops grown for fuel. The answer to that conundrum might be the microscopic plants known as algae. The tiny plants are not typically a food crop, are capable of producing 60 percent of body weight as oil under the right conditions, and can be grown in salt or wastewater, says David Daggett, Boeing's technology leader for energy and emissions.

Algal oil can also be precisely tuned via genetic modification, or good old-fashioned breeding, to be the equivalent of crude oil. A host of companies, from San Diego-based Sapphire Energy to San Francisco-based Solazyme, are now experimenting with this potential fuel of the future.

Bio-jet fuels have delivered consistent high-quality results in ground tests and experimental flights. These fuels seem to have overcome the problems that their energy density might be too low (think ethanol versus gasoline) and that they could gel at the low temperatures found at high altitudes (think diesel on a cold day). “All the characteristics are here to make it a very high quality fuel,” says Billy Glover, managing director of environmental strategy at Boeing. “The fuels we’re testing now have equal or better energy content than the Jet A requirements.”

Tim Zenk, vice president of corporate affairs at Sapphire Energy, said the company hopes to produce 300 barrels of oil from algae grown in brackish ponds at its test facility in New Mexico by 2011. In five years, the output should reach 10,000 barrels a day, costing between $60 and $80 dollars per barrel, he says, compared to more than $300 per barrel today for the algae industry as a whole.

Chemical engineers at the University of North Dakota’s Energy & Environmental Research Center have also successfully turned oil from canola, coconuts and soybeans into jet fuel that rivals the conventional
We believe we have a path for achieving biofuel approvals at a 50 percent blend level over the next two years.”
liquid, U.S. government tests show. And facilities to refine such algal oil are already being built. UOP — a refinery business of Honeywell that processed the biofuels used in the Continental test flight — opened the first “ecofining” facility in Livorno, Italy, last year, with a capacity to eventually produce 100 million gallons of diesel fuel for ground vehicles. A Portuguese company, working with UOP, is building a second “ecofining” facility in Sines, Portugal.

“Going to biofuels doesn’t mean we have to make compromises,” says chemist Jennifer Holmgren, general manager of the renewable energy and chemicals business for UOP. “We are already making fuels that look exactly like the real thing, or better. The real limitation is going to be feedstock.”

Industry and the U.S. government are working on a solution to that problem, through a partnership dubbed the Commercial Aviation Alternative Fuels Initiative (CAAFI). As part of that group, the Federal Aviation Administration’s chief scientific and technical advisor, Lourdes Maurice, testified at a Congressional hearing in March that “we believe we have a path for achieving biofuel approvals at a 50 percent blend level over the next two years.”

She also argued that bio-jet fuels represent a unique opportunity within the transportation sector, because air travel relies completely on energy-dense liquid hydrocarbons distributed to a small number of locations. Supplying biofuel to just 35 major airports in the U.S. would cover 80 percent of all jet fuel use in this country, Maurice said.

Any of today’s biofuels produced in quantity would still have to be blended with jet fuel because they lack aromatics — the hydrocarbon rings common in petroleum-based jet fuel that interact with seals in engines, helping swell them shut. “We fully expect that the first fuels will be 50–50 blends or less,” Boeing’s Glover says.

But even such a blend would deliver significant climate benefits. According to Glover, camelina is a particularly promising biofuel source, with one camelina-jet fuel blend reducing carbon emissions by more than 80 percent. Such a blend would also not require any modifications to existing aircraft engines or infrastructure.

That was certainly the case for the FAA’s experimental flight of the Continental 737-800. Engine shutdowns at altitude did not phase the bio-jet fuel, nor did sudden accelerations and decelerations. By the time Jankowski brought the plane back down to Bush Intercontinental at 1:45 p.m., roughly two hours after takeoff, he had burned through some 3,600 pounds of the biofuel, slightly less than the 3,700 pounds of regular jet fuel in the other engine.

“The airplane performed perfectly,” he said at a press conference afterwards. “There were no problems. It was textbook.”

Correction, June 18, 2009: An earlier version of this article incorrectly stated the amount of jet fuel that U.S. commercial airlines burn on a daily basis. The correct figure is approximately 50 million gallons of jet fuel per day, at a cost of roughly $150 million.


David Biello has been covering energy and the environment for nearly a decade, the last three years as an associate editor at Scientific American. He also hosts 60-Second Earth, a Scientific American podcast covering environmental news. In previous articles for Yale Environment 360, Biello has written about how geothermal technology and solar thermal technology can help meet the world’s energy needs, and about the resurgence in dam construction worldwide.

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David MacKay in his book, Sustainability-Without the Hot Air (see, states that the projected yield of biodiesel from jatropha is 1,600 liters per hectare per year (or a low 0.18W/square meter). It would be useful to know the time that it takes to grow the 242 gallons of jatropha oil per acre quoted in the current article as well as the conversion between jatropha oil and biodiesel to make a comparison with MacKay's number.

However, using MacKay's number, I calculated that, to replace the total U.S. aviation fuel requirement of 240 million U.S. gallons per day with jatropha biodiesel, it would take a suitable growing area approximately 25 percent of the land area of the U.S. excluding Alaska (i.e., 25 percent of 8.15 million square kilometers). Even to replace a quarter of the regular aviation fuel with this biodiesel would require an enormous area.

Biofuels from waste organic material or grown in space that has no competitive social, commercial or environmental service potential, yes, but surely this will fall well short of substituting for the 60 billion gallons of aviation fuel used annually by the world's planes? In an equitable world, it seems as if there will be a lot less flying being done if biofuels are to be the major energy source.

Posted by Rick Row on 11 Jun 2009

The reports of present planetary damage and future prospects indicate we must stop contaminating the ecosphere as a growing emergency. It would seem jet aviation will not be efficient enough for conventional use in the near future. Time to build some great sailing ships for the next decade when restrictions on carbon will be our only salvation.
Posted by James Newberry on 15 Jun 2009

Can you explain how a U.S. airline industry with total annual revenues of $100 Billion burns 240m gallons of $3 jet-a fuel a day? Isn't that over 80 billion gallons (supposedly costing $240b) per year?
Posted by marc on 17 Jun 2009


Thanks for catching my slip-up. I used the global figure mistakenly, in place of the U.S. only numbers. You can find a lot more precise data on this from both the industry and the government at:

2008 figures on fuel use from the Air Transportation Association:

2006 figures on fuel use (state by state) from the Energy Information Administration:

Doing the math, that means airline companies are spending more than half their revenue just on fuel...

Posted by David Biello on 18 Jun 2009

Aviation fuel amounts to less than 8 percent of liquid fuel burned world-wide. The uncomfortable truth is that we need to wean our cars off oil to make any difference at all. Wasting effort on high profile-small results projects like this divert attention from the need to convert the global ground fleet to methanol, preferably synthesized from above-ground carbon. (And, of course, the liquid fuel problem is itself dwarfed by the coal-fired power plant problem)
Posted by Julian on 19 Jun 2009

We might confront the emissions problem
caused by the world's airlines with biofuels - but
how about the impact of the injection of
megatons of pollution into the atmosphere at
30K feet?

If we are to truly deal with the environmental
impact of air travel, then we will not accept that
heavy craft pushed by jet engines is an answer.
On ground high speed rail combined with lighter
aircraft might salvage something of the
airline industry, might not. But the switch to
biofuels is another attempt to continue a
thoroughly unsustainable industry, born out of
the very crucible of the oil age. The very model
is not sustainable.
Posted by kd brown on 25 Jun 2009

Not mentioned as a potential source of biofuels feedstock for making jet fuel is wood wastes namely, forest residue, pre-commercial thinnings, sawmill waste, and waste lumber from construction sites and landfills. These cellulosic wastes are readily gasified, especially if torrefied first and the resulting clean syngasconverted into F-T liquids and/or jet fuel. This type of biofuels feedstock is not crop dependent and will not competete for land use with food crops. The thermo-chemical pathway for producing biofuels in this manner are proven. The primary drawback is the limit on amounts of wood wastes available and associated costs. But early indications are that this approach could be commercially viable and should be included as a potential source for some of the clean JP-8 that will be needed.
Posted by Tim Sklar on 08 Jul 2009

I am concerned by the world looking at biofuels as an alternative to regular fuel. Biofuels, if made from algae and non-food plants, is good as long as they don't contest with food plants over land, irrigation.

Higher biofuel demand in the United States and the European Union has not only led to higher corn and soybean prices, it has also resulted in price increases on substitution crops and increased the cost of livestock feed. In last two years, the price of corn in the U.S. has more than doubled, driven partially by demand for alternative fuels.
Posted by Amy on 19 Aug 2009

The cost to have the Bio Jet Fuel derived from any type of feed stock will be definitely not cheaper than the current fossil sources.

Are the Aviation industry willing to pay/absorb the high cost of the Biofuel?

There is no way that the feed stock for Biofuel could be cheaper than the current fossil fuel. The Food versus Energy will be more tension as growing energy crop (Jatropha,Palm oil or Cane) will have to steal the land from the food production since it was clearly proved that Growing energy crop required the reasonable piece of arable land.

It is a zero sum game either to grow more food crops to feed to people or grow more energy crop to serve the energy demand purpose.

Posted by Chumroen Benchavitvilai on 07 Nov 2009



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