Climate Change and Aviation Fuel: A Tough Problem to Solve
Large aircraft require high energy fuel, and lots of it. But jet fuel is very difficult to clean up to satisfy climate protection imperatives, which has led to a major dispute in the US over the role coal-to-liquids and other alternative aviation fuels may play. Congress, the US Air Force, the major airlines, the US Environmental Protection Agency, its Federal Aviation Administration, a special Defense Department task force, coal-state senators, and many, many others are getting into the dogfight, which may go on for a long time.
With all the publicity aircraft greenhouse emissions are receiving, one might conclude that they rank right up there with electrical utilities, vehicle emissions, and other prominent categories in terms of greenhouse threats. In fact, US aircraft operations account for 10 - 12 percent of greenhouse emissions from the transportation sector and for only about three percent of total US greenhouse emissions, which is also about the total percentage contribution to greenhouse gases from aviation worldwide. The difficulty is, controlling aircraft carbon emissions is a particularly intractable problem, and the problem is going to become much worse over the next few years as demand for air travel and transport doubles or even triples by 2025. The issue is exacerbated by scientific uncertainty about just how much more potent at high altitudes aircraft emissions are in causing the greenhouse effect as compared to emissions on the Earth’s surface.
The airline industry has done a great deal already, however, to increase its efficiency and lower the rate of increase in greenhouse emissions per air mile traveled. The industry claims that improvements in operational efficiency over the past 30 years have reduced carbon dioxide emissions 70 percent in the course of improving fuel efficiency 110 percent. The most promising pathways at present to further reduce the carbon footprint of aviation involve improved air traffic control systems, on-ground aircraft operations management, lighter engines and more aerodynamically designed aircraft, and flight altitude and speed adjustments. Still, attempts to improve jet fuel composition and performance have received the lion’s share of attention in recent months.
Finding less climate-challenging fuels for today’s jet fleet is proving to be a particularly challenging and controversial topic. Some promising experiments in fueling aircraft reminds one of a trip to a botanical garden, to a marsh, or to the supermarket, or of the early days of flight at Kitty Hawk. Recent forays include biofuels derived from babassu nuts, coconut oil, algae, or the central American plant, jatropha (a relation of castor oil). A very light, albatross-like solar-powered aircraft is under development in Germany, while Boeing has actually flown – for twenty minutes at 60 miles an hour – a manned aircraft powered by hydrogen fuel cells and lithium battery-stored electricity. But the major battle over alternative aircraft fuel is taking place over fuel liquids derived from coal or oil (tar) sands.
Coal-to-liquids (CTL), whether for aircraft or for other consumption as a fuel, is hardly new. Germany pioneered the process in the Second World War, and for the past nine years South African Airways has flown its jets on a 50-50 mixture of CTL synthetic and ordinary commercial fuel. The US Air Force has completed a test program very much like the South African fuel mix, using 50 percent Fischer-Tropsch synthetic fuel and 50 percent commercial fuel. Even B-52s can safely burn the fuel.
The Air Force and members of the Senate and House from coal-producing states, not to mention proponents of tapping the vast reserves of oil sands in Canada, are pushing strongly for development and use of CTL aviation fuels. The difficulty is, among other things, that a lifecycle analysis conducted by the US EPA found that CTL fuel releases 118.5 percent more greenhouse gases than conventional fuel (EPA, 2007). Perhaps carbon capture and sequestration technology, were it to be developed, could be used to overcome this large carbon deficit? No, said EPA, even after going to the difficult and expensive effort of capturing and sequestering CTL carbon compounds, emissions would still be 3.7 percent greater than for conventional petroleum. The Defense Department has already asked MIT to study the lifecycle carbon profile of CTL production and use, and Senator Lautenberg intends to re-insert in the Federal Aviation Administration funding re-authorization bill making its way through Congress a provision requiring the National Academy of Sciences to organize a study committee to address the question. While these studies are pending it may be correct to say that the jury is still out on the climate implications of CTL and other alternative aviation fuels, but it is clear that widespread adoption of CTL and oil sands to liquids fuels would be accompanied by major environmental challenges.
The Air Force is particularly partial to CTL as a source of aviation fuel and is aggressively pursuing its development. However, a major study done by the Defense Science Board Task Force on DoD Energy Strategy at the request of the Office of the Under Secretary of Defense for Acquisition, Technology, and Logistics, titled “More Fight – Less Fuel,” has concluded that domestically produced synthetic fuel will not contribute to the DoD’s most critical fuel problem – delivering fuel to deployed forces. The Task Force, co-chaired by James Schlesinger and retired General Michael Cairns, wrote that full carbon life-cycle analysis should be performed and that synthetic fuels should have a carbon footprint less than conventional petroleum fuels before they are adopted.
This last remark may be directed at a DoD-commissioned legal analysis attempting to show that in the Energy Policy Act of 2005, Congress did not intend for the military services to be considered as “federal agencies.” Why? Because section 526 of the 2005 law bans federal agencies from purchasing any fuels that produce higher levels of greenhouse gases than conventional jet fuels. (This provision is kicking up sand in many quarters and may not survive the political pressure that is being brought to bear.)
The EPA plans to join with the FAA in considering regulation of aviation greenhouse emissions in the course of the climate “town hall” comment period that EPA has called for to gather thoughts about using the Clean Air Act to broadly regulate greenhouse gas emissions, a topic we have covered in an earlier blog. The European Union first tried to ignore aircraft greenhouse emissions in its first round of actions under its climate authority (the issue, is, as we said above, a very difficult one), but it is now considering requiring airlines to participate in the emissions trading system.
The debate over how the US will attempt to come to grips with the difficult issue of direct aircraft engine emissions of greenhouse gases is just getting started.
