Hydrogen for Boeing

Boeing is developing an unmanned plane that would use liquid hydrogen to reach altitudes topping 60,000 feet and stay there for days at a time.

The plane is one of several alt-fuel aircraft that Boeing, which earlier this year tested a hydrogen fuel cell airplane, is working on. It uses an internal combustion engine which burns hydrogen. It has been tested on the ground in the lab under the high altitude conditions.

As it gives out mostly water vapour, which is also a greenhouse gas, but does not have carbondi oxide’s staying power and only has a minor direct warming effect, hydrogen could be considered a better fuel than the normal aviation fuel. It is also light.

Liquid hydrogen is used in rockets where it is mixed with oxygen and burns. The problem with liquid hydrogen needs much more volume than other fuels to store the same amount of energy. It takes roughly four liters of LH2 to match the energy content of one liter of jet fuel. The fuel cannot be carried in the wings as it will have to be large and will affect the lift. Boeing plans to try the fuselage for storing the fuel.

Combustion of fuel in aeroplane engines results in emissions of carbon dioxide (CO2) and nitrogen oxides, (termed NOx), as well as water vapour and particulates. Aviation emissions have a greater potential for mischief as they can instigate various chemical changes at that height. It is the emission of NOx, water vapour and particulates at altitude that account for the extra impacts of aviation emissions. Nox also combines with sunlight to form ozone.

Aviation is the fastest growing cause of global warming. The amount of carbon dioxide emitted by air travel doubled between 1990 and 2004. That is totally incompatible with the need to reduce carbon emissions by 60% by 2050.

But it is not possible to ask people not to fly or to make it a costly option just to cut down on flights. A better solution touted is to improve fuel efficiencies, the air traffic control gets smart, routes get straighter, etc. All these with a proper implementation of emissions trading on aircrafts and research on friendlier fuels can bring down fuel used and emissions.