Aero-Astro and Energy

At her 2005 inauguration, MIT President Susan Hockfield said that it is "our institutional responsibility to address the challenges of energy and the environment." Throughout MIT, researchers are developing means to transform the global energy system to meet the needs of the future and to improve existing energy systems. In our new Web series Aero-Astro and Energy, we take a look at some of these efforts within the Aero-Astro department.

MIT research looks at alternative fuels for aviation

Options could be cleaner, more efficient, and sustainable

By Bill Litant and Jim Hileman

With the world’s aircraft burning more than 141,000 gallons of fuel every minute, the aviation community is increasingly concerned about fuel’s burgeoning cost, volatile supply, and environmental impact. Yet, there is also optimism among some in the community. There is growing evidence that there are options for traditional petroleum products; options that could offer sustainability, reduced dependence on imports, cleaner burning, and cost stability or even reduction.

Developing alternative fuels for aircraft is a tricky business, researchers face myriad challenges. For example, weight is an issue when you have to lift your fuel supply into the air. Safety is a big concern — you can’t pull a balky Boeing or an Airbus to the side of the road and pop the hood. There’s not a lot of concern when your tailpipe emits water vapor at ground level, but there are climate impact concerns when H2O is emitted into stratosphere. And, tens of thousands of airplane engines rely on current fuels’ specific properties to keep parts lubricated, sealed, cooled, and in otherwise good running order.

The Federal Aviation Administration, which has an inherent interest in aviation economics, safety, and environmental impact, is adamant that solid research underlies the regulations and policies it promulgates. To that end, the FAA, along with NASA and Transport Canada, funded a new Center of Excellence research collaborative: the Partnership for AiR Transportation Noise and Emissions Reduction, headquartered in the MIT Aeronautics and Astronautics Department under the direction of Professor Ian. A. Waitz.

Tasking PARTNER to explore a number of aviation environmental issues (e.g., noise and emissions) the FAA asked the MIT experts to explore the ramifications of proposed alternative aviation fuels. The endeavor’s goal is to identify energy sources and processes that could provide a stable jet fuel supply at reasonable cost and reduced environmental impact.

The central questions of the PARTNER study are: how can we reduce aviation’s impact on global climate change and improve local air quality, and how can we combat volatility in jet fuel prices? The study, currently in its final stages, is focused on fuels that could become commercially available within 10 years. PARTNER is examining a array of alternative fuels — low sulfur jet fuel, synthetic liquid fuels from coal and biomass (organic matter), ethanol, and biodiesel — and any one that is considered as a viable alternative must meet a list of qualifications to avoid conflict with environmental and safety regulations, and airline economics.

Today’s ubiquitous aviation fuel is a kerosene-type fuel called “Jet-A.” Jet-A offers considerable energy per weight and volume, is safe to handle, is designed to ensure prolonged engine life, is compatible with the existing storage and delivery infrastructure, and was historically low-cost.

Many alternative fuels pose serious hurdles. For example, biodiesel — increasingly popular for earthbound vehicle use — thickens considerably at the low temperatures encountered at high altitudes. Alcohols pack comparatively little energy for given weights and volumes. Cryogenic fuels, like liquid hydrogen, pose so many obstacles (for example, they are completely incompatible with the existing infrastructure) that they are unlikely to be practical within the 10-year criterion and, are therefore, not under PARTNER’S consideration.

PARTNER’s evaluation includes the full cycle of fuel production and use: initial energy harvesting/resource extraction, production and transportation, storage, burning in engines, to any end-of-use/disposal issues. PARTNER is also considering the full range of health, welfare and ecological impacts, including effects related to changes in non-renewable resource use, air and water quality, community noise, exposure to hazardous materials, and climate change. PARTNER’s research follows the established methodologies for transportation fuels life-cycle analyses where the environmental impact of fuel production is considered separately from the impact of combustion emissions.

PARTNER’s alternative fuel assessment is performed using new, highly sophisticated software that it developed, the Aviation Environmental Portfolio Management Tool, to estimate changes to aviation impacts on local air quality, global climate, and community noise. APMT is a comprehensive software suite that makes possible a thorough assessment of aviation environmental impacts. It quantifies the complex interdependencies between seemingly disparate aviation-related noise and emissions effects. Outputs are comprehensive cost and benefit estimates of aviation industry economics and environmental impacts for a range of assumptions and stakeholder viewpoints.

In a report to be issued in conjunction with the Rand Corporation in the Spring of 2008, PARTNER will offer its analysis of life-cycle and environmental effects, and delineate options for development and production of strategic quantities of aviation fuels.

For more information on PARTNER, its multi-university collaborative network, and its research visit http://www.partner.aero or email info@partner.aero

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Bill Litant is the MIT Aeronautics and Astronautics Department and Partnership for AiR Transportation Noise and Emissions Reduction communications director. He may be reached at wlitant@mit.edu. Jim Hileman is a research engineer for the Partnership for AiR Transportation Noise and Emissions Reduction studying alternative fuels. He may be reached at hileman@mit.edu.