Last month, in an 8-page document plainly titled “Alternative Fuels for Commercial Aircraft”, Boeing presented their estimation of the alternative fuel sources that could ‘relieve worldwide pressure on crude-oil derived fuels’ and drive air travel to carbon neutrality.

The biofuel debate has largely glossed over the ‘friendly skies’ while high fuel prices continue to take their toll on the industry. No biofuel we have yet can step up to the plate. Ethanol collects water and corrodes the engine and lines while biodiesel freezes up in cold weather (ie: cruising altitude). Don’t forget pilots’ general resistance to change and a life and death dependency on reliable fuel, and aviation biofuels don’t have a leg to stand on.

“There are a lot of questions to be answered and one of them, frankly, that has been answered so far is that ethanol is probably not suitable for airplanes,” Boeing Commercial Airplanes environmental strategy managing director Bill Glover said during a Star Alliance conference in Copenhagen.
“That would require changes to the airplane - (ethanol) doesn’t have the energy content and it has some other properties that are incompatible with the systems in the airplane.
“But we can, it looks like, develop something that is more like a biodiesel that has some promise.”

This isn’t going to happen right away though, and Boeing sees possibilities for 3 different time tables: near, mid-range, and long-term. In the near term, a ‘drop-in’ fuel is needed - something to replace regular fuel as quickly as possible. Boeing thinks this might be a blend of kerosene and synthetic diesel produced via Fischer-Tropsch process (I had to look it up too). Though this could alleviate some dependence on crude, synthetic diesel is still nonrenewable and without CO2 sequestration (mentioned as a possibility in the report) it can actually double net CO2 emissions (being typically manufactured from coal or natural gas) .

In the mid-term (10-50 years), Boeing suggests biofuels will make up a much larger percentage of jet fuel in blends with synthetic diesel or Jet-A (standard Jet fuel). The significant barriers to this are well-known: lack of farmland for contemporaryfeedstocks (soybeans, etc) and competition for food, fuel gelling problems, poorer heat stability in the engine, and questionable suitability for storage.

But the long term is where things get really exciting, and Boeing is extremely optimistic about the potential of algae:

With the potential for algae of providing 10,000 gal/acre/year, some 85 billion gallons of bio-jet could be produced on a landmass equivalent to the size of the US state of Maryland. Moreover, if these bio-jet fuels were fully compatible with legacy aircraft, it would be sufficient to supply the present world’s fleet with 100 percent of their fuel needs (fig. 13) as well into the future.”

Yes, Boeing actually said that: 100% of world aviation fuel needs. Details are sparse at this point, and it’s unclear what this algae bio-jetfuel will be, but Boeing seems satisfied by the prospect and appears sincerely concerned about global warming. The take home message was that:

Long-term solutions will need to dramatically reduce the emissions of greenhouse gases. Therefore, alternate fuels with low to zero carbon content, such as liquid hydrogen or liquid methane, might be used.

Liquid fuels like these could be the next step, potentially produced by nuclear or preferably, solar power.

It’s good to hear some noise coming from the aviation industry, and perhaps algae won’t take 50 years to become the fuel source of the future.

Latest update on Algae Biodiesel: Algae Biodiesel: First Industrial Algae Plants Go Online

For more on this topic, see also: Algae Biodiesel May Soon Be Reality

Alternate Fuels for use in Commercial Aircraft
Algae May become the Aircraft Fuel of the Future (May 25)