Presentation Abstract: The Conflict Between Aviation
Growth and the Environment: An Industry/ Research Perspective

Question #1

Interviewer: Vicki Pellar-Price
Policy decisions regarding emission mitigation correspond directly to cost, technical feasibility and safety concerns. Though options have been proposed such as higher fuel taxes, emission charges, emission limitations, increased emission standards, retrofit mandates, voluntary actions, and demand management, the belief is that these options will be negotiated into policies that will include technological, operational strategies for improvements to system efficiencies and emission reductions. Which of these options would the industry be most likely to implement toward reducing emissions and maintaining industry competitiveness? The National Resources Defense Council (NRDC) suggests there should be government imposed industry laws which apply to reductions of emissions through accountability, emission charges and or limitations. Will that be enough to alter the effects of increased demand on the environment?

Bruce Anderson- My role is strictly to participate in some of the field experiments and try to characterize the emissions from various sources of aircraft and to contribute both findings and my understanding in reports like the ICAO that you read. And also to contribute to NASA interrim-reports on subsonic emissions and from subsonic and stratospheric aircraft. I can’t speak to NASA policy or conclusions. Everything I’ll say will be my own opinion, but I will try to speak to the consensus of opinions on different things. But I can’t illuminate the national policy on aerosol and aircraft emissions.

David Kittelson- I’m not involved in policy; I’m involved in experimental measurements. I only am impacted by policy as much as I disagree or agree with it. I’m not the one making it.

Bruce Anderson- Right. Well I think all of us are in the trenches trying to develop an understanding of the processes that create aerosol particles in combustors and in engines. The information that we gather and the understanding we gain will help to improve technology. At least that’s my hope that we will begin to understand how an aircraft or a traditional engine produces sulfur or soot particles, so that engineers can use that information to develop a better combustor in order to reduce the emissions of these unwanted trace species. That’s our particular role in the national effort to characterize and control emissions.

David Pui- Dave and Bruce have probably heard all the counter arguments and arguments and understand the science and the technology, but in terms of policy we can’t really speak to that.

Bruce Anderson- What I think I can do is to describe what NASA’s efforts are to reduce aviation emissions. NASA’s role is very much shaped by the administration’s policy on pollution research.

David Pui- Maybe Bruce can state what NASA’s interest is in this whole measurement experiment.

Bruce Anderson-Well, several years ago NASA's aeronautics directorate had two programs called Advanced Subsonic Technology (AST) and High Speed Civilian Transport (HSCT). The focus of HSCT was to develop technology for making supersonic civilian transport economically feasible. And the subsonic technology program (SCAST) was to develop improved airframe and powerplant technology for subsonic aircraft; indeed some of this is in use now in commercial subsonic aircraft. Portions of the funding from both programs were allocated to set up the "Atmospheric Effects of Aviation Project (AEAP)" that sponsored environmental research to assay what the impact of aircraft, particularly of a standing subsonic fleet would be on the atmosphere.

Some AEAP objectives were very similar to those of the assessment program they instituted around 1970 when the Concord was first conceived. Then NASA conducted a study to see what impact the supersonic fleet would have on stratospheric ozone in particular. And at that time the ozone cycle on the stratosphere wasn’t completely understood. That was back before the concept of an ozone hole was even considered. But a lot of work was done to figure out much NOx was going to be deposited, anywhere from 15 to 20 kilometers up in the stratosphere, and what impact that might have on ozone and other stratospheric constituents. The program was dropped more or less because the technology was too far behind to even make a supersonic fleet economically feasible.

In the late 80’s they resurrected study of supersonic technology, starting the HSCT program, because they thought that technology had advanced to the point that supersonic transport might possibly be commercially viable. Again, they applied a portion of that funding toward studying the technology and a portion for assessing the environmental impact of a fleet of high flying aircraft. The environmental work was primarily focused on evaluating what the impact of the supersonic aircraft emissions would have on ozone and radiation characteristics of the stratosphere. AST also allocated money to AEAP. Their interest was in assessing the impact of current and projected fleets of subsonic aircraft on atmospheric radiation and ozone, hydrology and climate.

I think AEAP was active from 1993 to 2001 at which point the aeronautics division within NASA took a big hit in funding so they dropped all the studies dealing the with atmospheric effects of aviation. A portion of the subsonic study continued to receive funding from NASA's office of earth sciences, but at a very low level, and most of the focus was on using 3-D models to assess the impact of aircraft emissions on climate and ozone distributions.

But right now NASA’s funding of environmental impacts of aviation is at a very low level. The Aeronautics Directorate has an Ultra Efficient Engine Technology program from which Chowen Wey at NASA Glenn receives a small amount of money to study and understand emissions from new combustors that are being developed as more efficient power sources for jet engines. So they are studying the NOx emissions and the particulate emissions from these and we’ve also got a small amount of funding from Chowen and Don Anderson in the Radiation Sciences office at NASA to conduct the Experiment to Characterize Aircraft, Volatile Aerosol and Trace Species Emissions ( EXCAVATE) Mission that David Pui has described. Otherwise there is no new funding that has been injected into aircraft emissions studies from NASA and I don’t think it’s NASA fault as much as it's our budget that has been flat for the last ten years, and certain items within the program like the space station and the space shuttle are taking an increasing portion of the budget and leaving less for the other programs.

That’s kind of the situation. The Atmospheric Effects Aviation Program Project (AEAP) sponsored a number of studies during the 8 year period it was active in assessing aviation impacts for subsonic testing that included some of the ground based measurements that Professor Pui participated in and some studies of contrails and air pollution levels over the Continental US and the North Atlantic flight corridor. At the same time NASA was doing these types of studies the Europeans have conducted a number of studies to look at what levels of pollution commercial aircraft are generating over Europe and to look at the impact of various fuel formulations on particulate emissions from aircraft. I think part of the drive for Americans to achieve an understanding of turbination engine emissions was for fear that the Europeans would find some smoking gun that would give Europeans an advantage over American technology, in terms of engines and air frames. I think the Europeans are still doing some studies on aircraft emissions but not at the same level they were doing five years ago. If you look at the literature now, the number of papers done by American scientists on aircraft emissions has dropped way down. So even though it’s not a solved problem there are certain conclusions that led everybody to believe that there really wasn’t any smoking gun there; there was nothing that was going to create an ozone hole, it’s just a gradual process; aircraft is just like any other internal combustion engine or diesel engine, they generate a fairly known amount of trace gases and aerosols. The more of them you have flying, the more of these they’re going to create. That’s my perception of what’s going on within NASA.

David Pui- Bruce that’s an excellent overview of NASA’s interests. This gas turbine engine technology has improved a great deal. I still remember years ago when Gorbachav came to Minnesota. I paid a lot of attention to his visit, when he arrived and what he did. And when he took off, I remember seeing him give the farewell speech and then he got on his aircraft and took off and I remember this huge black plume spew out of the plane. For ten minutes it spewed black soot.

Bruce Anderson- Those were old, low by-pass turbo jet engines that generated a lot of large soot particles. They currently use "smoke number" measurements to regulate soot emissions; basically you suck the engine emissions through a piece of filter paper and then measure the light attenuation through the filter. If the filter comes out black you know the engine is not running properly or doesn’t meet the requirement. So, they came up with techniques for reducing the smoke numbers from engines. Professor Kittelson knows more than I do about this. But, the more modern engines certainly generate probably an order of magnitude less soot than the older turbo fans engines did. There have been a lot of improvements in technology that reduce the particulate emissions or at least the visible particulate emissions.

David Kittelson -Well yes, a lot of what I’ve been doing with diesels is looking how improving engines technologies tends to make the particles smaller and as they get smaller you do have much less mass and much less of an optical signature, but sometimes you don’t actually emit much less total numbers of particles. That’s one of the concerns with diesel engines: is that these very tiny nuclei, that probably aren’t even composed of soot, but rather of hydrocarbons and sulfuric acid, might have some adverse environmental effects and that’s been the driving force behind the diesel work I’ve done in the last few years. When I look at the size distributions and so on and compare them to your work and Pui’s there are amazing similarities between some very modern diesel engines and the gas turbine emissions.

It does seem that the gas turbine emissions are much higher under these off-design conditions, associated with idling and take-offs than they are when you’re up in the stratosphere cruising. I was at a conference in Zurich a few weeks ago where they had somebody from one of the big stationary gas turbine companies in Europe and those engines would be running at design point on the ground and the particle mass on the ground was considerable lower than that of ambient air and so on design a gas turbine engine could be extraordinarily clean. I guess my concern and the concern I’ve heard expressed at meetings is whether or not engines running off design at airports might be a local hotspot.

Bruce Anderson- Well I think that’s a reasonable possibility. NASA’s interest has primarily focused on what aircraft do in the mid to upper troposphere and lower stratosphere. When the engines are operating on their design point, they’re all revved up, and your not continuing to go from idle to full power like you would be in a taxi mode in an aircraft. I’m sure Professor Pui has discussed with you some of the results from our Excavate experiment. Such as, when you are revving and idling an engine you do get considerable quantities of basically raw fuel or small particles generated that are mostly organic. Yes, those are some of the things we don’t understand very well and it’s something that NASA has not really paid much attention to. The primary objective of the recent study we did at Langley was to look at a B757 engine emissions and try to simulate the in-flight conditions, the fuel flow rates and temperatures that an engine might be at in flight. But, during the process of setting this up we realized that at airports the engines weren’t going be operated like that, so we gathered a lot of data to try to characterize the non-optimum emissions from the engines. Those are the types of studies we need more of, because I think Professor Kittelson is right the airports themselves may be the hot spots for local air quality and human impacts. The FAA is interested in aircraft emissions in terminal areas, but they don’t really have any money to sponsor research. A guy called me from the FAA and they wanted to use our data in a dispersion model to determine what the PM2.5 levels might be in the vicinity of an airport. But that’s not something that’s received a heck of a lot of attention. Aren’t you getting involved in that David?

David Kittelson- Well you know we actually had a grant from the Minnesota Department of Transportation n to do some particle measurements near the airport. The airport commission would not let us anywhere near; they didn’t want us anywhere near the property. So that project collapsed.

Bruce Anderson- Well that’s the problem, most aviation industries are very sensitive to anything that might lead to further regulations. They want to preserve their competitive edge and be able to operate as economically as possible. I know for a while there was talk of using tow-carts to pull aircraft onto the runways and have them start their engines just before take-off instead of having these long lines of aircraft with their APBUs, (Auxillary Power Units) running and their engines alternately powering up and idling down. I think there is some sensitivity to what people might find when they start looking in detail at aircraft emissions in terminal areas. I think that it’s a subject that NASA is willing to address if there was some level of funding to support it. The type of work that gets done is not so much selected by the scientists within our organization as it is with the level of funding available and the funding priorities.

David Pui- Bruce I heard you and Dave both tell me about the recent conferences where investigators talked about comparing the three days after 9-11 when all the aircraft were grounded and comparing prior to 9-11 when aircraft were flying normal operations. I wonder if anyone of you can summarize what this investigation has revealed?

Bruce Anderson- Well I know they looked at the temperature variability at ground sites in the central US and they found that the surface temperature had a much larger swing between day and night during the time the planes were grounded as opposed to when they were operational and flying. So the conclusion was that the contrails had a dampming effect on surface temperature variations. I’m not sure where that study appeared and what the exact implications are for climate change, but the indication is that the contrails are probably trapping heat.

David Kittelson- I actually thought it was sort of the opposite conclusion: that they were raising the nighttime temperatures but they were reducing the daytime temperatures and the net effect was a cooling effect rather than a heating effect.

Bruce Anderson-Well maybe your right about that. I know that the conclusion was that they were dampming the temperature variation.

David Kittelson- Yes that’s right and it was quite a significant effect. Phil Hoppke who runs the EPA center out in New York State told me about it. I still haven’t seen it in print.

Bruce Anderson- I think it may have been in Science News.

David Pui- Vicki seems to know where it was published.

Vicki Pellar-Price- It did appear in several local papers.

Bruce Anderson-Right. It did appear in our daily newspaper. Patrick Minnis is a fellow scientist here that understands the radiation effects better than anybody I know. He has published a lot of papers about contrail frequency and duration and radiative effects.

David Pui- Would you say based on this single study that it’s a good demonstration that yes, aircraft does have an effect on global radiation balance?

Bruce Anderson- Well it’s like you can ride around Minneapolis and make measurements of soot and you could say engines have a tremendous effect on soot levels in the atmosphere, but if you go out to Christmas Island you would see one soot particle every ten minutes or something. The central US is often blanketed with contrails, but extrapolating that to a global effect is problematic.

David Pui- So I should not say global.

Bruce Anderson- I’d say regional effect.

David Pui- Especially in the Atlantic corridor, east coast?

Bruce Anderson- You can look into those reports and see where those flight paths are concentrated over the US and North Atlantic. People have found that the frequency of cirrus clouds are much higher over those areas and that can be attributed to condensation trails from aircraft. But, how many watts perimeter squared change in radiative forcing at the surface that equates to, I don't know. People have made estimates of it, but I’m not familiar with those studies or findings.
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Question #2

Interviewer: Vicki Pellar-Price
Does new jet engine technology require fuel additives or formula changes?

David Kittelson- Certainly aircraft fuel consumption per passenger mile is a consideration in assessing efficiency.

Bruce Anderson- NASA and aviation agencies in the industry are trying to improve fuel consumption per passenger mile through deveopment of high thrust engines and cleaner airframes. Of course the industry itself uses aircraft that are half-full and that’s not efficient. As long as people travel by air travel it’s much more efficient than other modes of travel. There is a lot less CO2 per passenger miles than any other type of transportation. People are also traveling longer distances.

ICAO and NASA report the conclusion that the aviation industry is not going to significantly impact the global CO2 budget, or the water vapor budget in the upper troposphere. The areas that it could have an impact on from an upper atmospheric point of view are radiation and ozone. So those are the areas that they concentrated on. Of course Professor Kittelson and Professor Pui are more intimately concerned with the characteristics of particles that might be deleterious to human health than the NASA program is looking at.

I think Dave Kittelson has been involved in looking at sulfur particle formation in diesel engines; well it’s the same with jet engines. If you could get rid of the sulfur contamination in fuel you could certainly lower the particulate emission contamination in both diesel and turbine engines.

David Kittelson- And that’s happening in diesel engines; in 2007 there will be a 97% sulfur content reduction in diesel fuel.

Pui- Is there a similar initiative for new jet engines.

Bruce Anderson- The heating oil and diesel market drive the jet fuel market, they create more diesel fuel with less sulfur than jet fuel. It comes off the same refinery with a different fractionation.

David Kittelson- Yes, jet fuel is a different cut, although its not clear if hydro-treating which is what they use to get the sulfur down applies here. I don ‘t know that they do it to all the streams. For instance off road engines you might say get the same diesel fuel as on road engines, actually the off road sulfur standard is much higher, and there will be off road diesel produced that has 10 times more sulfur than on-road diesel fuel coming out of the same refinery. I think they take the fuel that they have to get the sulfur down and treat it more vigorously. So, it’s driven by standards.

Bruce Anderson-I don’t think the aviation industry is ready to set a more restrictive sulfur standard. Right now the max is 3,000 parts per million and the average sulfur concentration of jet fuel is around 400 parts per million and it’s tending to go down, but I don’t think they are going to set a standard or reformulate the fuel because it would make the fuel cost more.

David Kittelson- In this connection during the last energy crisis, there were a number of people who made a rather strong case for hydrogen fueled aircraft, arguing that unlike trucks, buses and passengers cars, where the volume of hydrogen really reduces the payload, hydrogen fueled aircraft which are sensitive to mass rather than volume, actually experience an increase in performance when converted to hydrogen, but of course there are lots of other problems. Is NASA doing anything with hydrogen engines?

Bruce Anderson- Probably so. Chowen Wey is involved in the Ultra Efficient Engine Technology Program at NASA Glenn. I know in the past they have investigated new engine technologies. In terms of fuel additives the Air Force has developed an additive that they call Plus 100 that they’ve put into fuel for all their fighter aircraft. It’s supposed to reduce the coking on their after burners, which they claim reduces the soot emissions, but what really happens is what Dave talked about, it results in finely divided soot emissions, so it's more difficult to measure and perhaps their impacts are even more insidious. But, I know that the Department of Defense has put out a call for proposals to reduce the soot emissions from gas turbine engines as well as diesel engines. So people are working on devices to install in the engines and different fuel formulations that will reduce soot emissions and perhaps organic aerosol emissions.



Question #3

Interviewer: Vicki Pellar-Price
The pressure is on for accountability. Organizations such as the ICAO are pressing for more stringent regulations on NOx emissions at national airports. The EPA proposed PM-2.5 regulations, which would provide a restriction on aircraft particulate emissions. The IPCC estimates aviation’s contribution to global warming at 3.5% and growing. The Kyoto Protocol to the United Nations Framework Convention on Climate Change seeks reduced emissions from industrialized countries from aviation fuels.

Engine efficiency increases NOx emissions. Contrails are often the result of greater engine efficiencies. An increase in contrails can increase radiative forcing, which can alter the climate and atmospheric ozone levels causing an increase in ultraviolet-B radiation. A result of this forcing, using GDP growth as a determinant for aviation’s contribution, and aviation will contribute to a mean surface temperature rise.

The Bush administration has backed away from the campaign promise to reduce levels of transportation related CO2 which contribute to impacts such as alterations in the chemical composition of the troposphere and stratosphere, upper atmospheric ozone depletion, changes in aerosol and particulate levels, the creation of contrails and changes in existing cirrus cloud cover. How will your research help to convince the government and the industry to address these serious environmental impacts now, both on the ground as it affects the air we breath, and atmospheric climate changes?

Bruce Anderson- Speaking from the position of a scientist, I’m not sure that people who develop budgets for the Federal Government take into consideration our findings. There is a long ongoing national debate on whether global warming is a reality or it’s just a cycle of the sun or some long-term cycle of the planet’s climate. The Bush administration has been dragging its feet about doing anything about CO2 emissions; I just read they have more or less coerced the EPA into not including taking any further discussion on CO2 and global climate change other than into a recent EPA report.

David Kittelson- Somehow the Europeans, who certainly have the same politics and problems, are taking global climate change very seriously. When you drive on the Autobahn in Germany next to the speed limit sign, signs read slow down, and protect the environment.

David Pui- The Green Party in Germany is very powerful. A lot of changes are the result of the Green Party initiative. One of the interesting things I learned when I spent time in Duesselbourg, Germany last year, as part of my sabbatical, was the use of wind power. I saw a whole bunch of wind powered generators in farm fields. This is Green Party initiative; they want to see these alternative energy sources used.

David Kittelson- Germany has a strong Green Party, but even the attitude of the rest of the world is that fuel should be more expensive and that we really should reduce CO2. It’s only in the US. The US stands out like a sore thumb compared to the rest of the world.

Bruce Anderson- Well we have a culture of consumption.

David Kittelson-That’s right, we have an energy policy that was started on the 1930’s expansion based on ultra cheap energy and we haven’t changed since.

Pui- Vicki, I don’t know if you’ve thought of this, but I always tell my students that water is more expensive than gasoline. Water costs $1.00 for half a liter; so one gallon, that’s four liters, costs $8.00 to get one gallon of clean water to drink.

Vicki Pellar-Price- Capitalism?

David Kittelson- American Capitalism.

David Pui- That’s easily 4 to 8 times more expensive than gasoline.

Bruce Anderson- There are other methods besides reducing pollution. We could develop alternative energy sources, promote conservation and then start thumbing our noses at these OPEC countries that hold us hostage for oil.

David Kittelson- It would transform the country, and yet there is no political will to do this. Zero as far as I can see.

Bruce Anderson- Yes, this is way outside of our expertise, but as a concerned citizen though it’s something I’ve thought about a lot. Fuel in other parts of the world is at least 2 to 4 times more expensive than it is here in the States and people don’t seem to be suffering from it. Yet, if gas goes up 15 cents a gallon here it’s a major crisis.

David Kittelson- Yes, I think the lobbyist who work against fuel price increases have sort of propagated hysteria associated with an increase in the price of fuel. There is the belief that an increase in fuel prices will make the economy suffer, and it’s such a firm belief that it actually does. But it’s not because the price is increased; it’s because people believe the economy will suffer. Then the stock market goes down of course because that‘s the belief that it will. But if you actually look at how oil prices propagate through the society, yes, it’s a factor and consumer goods are cheaper when oil is cheaper. But that doesn’t hold true for other areas; in Europe where the standard of life is good, fuel prices are higher.

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