In this week’s episode, host Kristin Hayes talks with Zia Abdullah, a program manager at the US Department of Energy’s National Renewable Energy Laboratory. Abdullah and Hayes discuss what sustainable aviation fuels are made of, how they are refined and manufactured, and how they compare to traditional jet fuel. Abdullah also discusses the challenges in store for the United States in reaching the federal government’s sustainable aviation fuel production goals for 2030.
Listen to the Podcast
- Sustainable aviation fuels should target long-distance flights: “In order to make an impact, we have to go after these longer-distance, long-haul flights … These long-haul flights cannot really be electrified because current battery technology is weight limited … If you were to take the energy content in the fuel tanks in an airplane, and you would store that much energy in a battery, the battery would weigh about 30 times the weight of the fuel … Hydrogen would require not only all the fuel tanks in the airplane, but also half of the fuselage—you wouldn’t carry passengers; you’d be carrying hydrogen. Hydrogen or batteries are not options, so really, our only option is energy-dense liquid fuels.” (4:07)
- Sustainable fuels require long-term planning: “Airplanes that are flying today will still likely be flying in 2030, and airplanes that are being sold today will most likely be flying in 2050. This means the sustainable aviation fuel that we make must be absolutely identical from a molecular perspective to the Jet A fuel that these airplanes use today, so that the current fleet can use it safely.” (11:16)
- Sustainable fuels create jobs: “We are starting a whole new industry in the United States. This is really exciting, because this will create a huge number of new jobs and help the GDP of the United States in a way that’s beneficial to our climate. It’s not going to be easy … It has to be done in a way that engages in a very positive way with existing industries that already work on the fossil side or on the farming side and get them to buy into this new vision and be leaders.” (19:03)
Top of the Stack
- “Climate Friendly Jet Fuel: 3 Strategies for Accelerating its Production” by Zia Abdullah
- “The economic outlook for converting CO₂ and electrons to molecules” by Zhe Huang, R. Gary Grim, Joshua A. Schaidle, and Ling Tao
The Full Transcript
Kristin Hayes: Hello, and welcome to Resources Radio, a weekly podcast from Resources for the Future. I'm your host, Kristin Hayes. My guest today is Dr. Zia Abdullah, Biomass Laboratory Program Manager at the US Department of Energy's National Renewable Energy Laboratory, or NREL. Dr. Abdullah is a mechanical engineer with extensive experience and accomplishments in thermochemically and biochemically converting biomass to fuels and chemicals. His experience includes more than 25 years of research and development in biomass conversion, as well as problem-solving, new product development, business development, and project management.
Earlier this year, I came across an article by Dr. Abdullah on the US Department of Energy's website about accelerating the production and use of sustainable aviation fuels. I think that's a topic that we haven't yet touched on Resources Radio, but we're going to give it a bit more attention today. Dr. Abdullah and I will be talking about what goes into sustainable aviation fuels. I mean that quite literally: we're going to be talking about biofeedstocks as well as the emissions profiles and scalability of these fuels. I want to note there's this rumor that cars running on certain biofuels give off the smell of french fries while operating. Let's find out what our future flights are going to smell like, shall we? With apologies for that rather odd french fry comment, stay with us.
Dr. Abdullah, thank you so much for joining me today on Resources Radio. It's really nice to talk with you.
Zia Abdullah: Thank you for the invitation to be on this podcast and the opportunity to talk about NREL's program on sustainable aviation fuels.
Kristin Hayes: I have to say I'm on a roll personally, having fascinating conversations here on Resources Radio with physical scientists like yourself, or engineers. I'm excited to sort of hear about your engineering background and how you came to focus on biomass and biofuels in your own career.
Zia Abdullah: My interest in biomass and biofuels started very early in my career. After my PhD, I joined Weyerhaeuser Company in Seattle, Washington. Weyerhaeuser is one of the largest private landowners in the United States, and, as Weyerhaeuser employees, we were always challenged to look for new opportunities for biomass because they grow so much biomass on their lands. On the other end they were interested in opportunities other than pulp paper and building products. That's what they do in their line of business, so that led to an interest in fuels and chemicals because those are large markets, and here we are.
Kristin Hayes: Here we are. As I said, it’s novel for us on Resources Radio to be talking about sustainable aviation fuels. One thing that I noticed in your article is this part in quotes: "When we talk about decarbonizing the aviation sector, increasing supplies of sustainable aviation fuel (SAF) is often at the center of the discussion."
Why is that the case? Why is sustainable aviation fuel so central to the discussion? A parallel question is, are there other decarbonization options available for aviation, or are we talking about less carbon-intensive liquid fuels? Are they the only game in town for this sector?
Zia Abdullah: If you look at commercial aviation and the greenhouse gas, or GHG, emissions associated with commercial aviation, about 95 percent of the GHG emissions in commercial aviation are produced by medium- and long-haul flights. If you're flying from Washington, DC, to Los Angeles, for example, those are long-haul flights. Regional aircraft, which are flying 100 miles or 150 miles or 200 miles, only produce about 5 percent of the emissions.
In order to make an impact, we have to go after these longer-distance, long-haul flights. For these airplanes, there's no other option than energy-dense liquid fuels. You may have read and heard a lot about electrification and hydrogen and so on powering airplanes. These long-haul flights cannot really be electrified because current battery technology is weight limited. Batteries are very heavy.
If you were to take the energy content in the fuel tanks in an airplane, and you would store that much energy in a battery, the battery would weigh about 30 times the weight of the fuel. If you use hydrogen, and you put that much energy in hydrogen, the hydrogen would require not only all the fuel tanks in the airplane, but also half of the fuselage. You wouldn't carry passengers; you'd be carrying hydrogen. Hydrogen or batteries are not options, so really, our only option is energy-dense liquid fuels.
Kristin Hayes: It's great to have a fine point put on that and why this matters so much. My next question for you, then, is what is considered a sustainable aviation fuel? What does sustainability mean here? What feedstocks are most common when we're talking about these sustainable fuels?
Zia Abdullah: It's a very precise definition. Sustainable aviation fuel has been defined by the International Civil Aviation Organization (ICAO). This is defined as a fuel that (a) achieves net greenhouse gas emission reductions on a life-cycle basis; (b) respects biodiversity conservation and ecosystems from where the feedstock is harvested; (c) contributes to local social and economic development; and (d) the source of the biomass for this fuel does not compete with food and water requirements for humanity. This one is really important.
The question is, How do we make SAF, and how do we do it? SAF is made by converting renewable feedstock to fuel molecules that are identical to conventional jet fuel, which is called Jet A. We use biology and catalytic conversions that are very similar to those that are already used in refineries.
The key difference is that in conventional refineries, crude oil is very similar, but in biorefineries, the feedstocks can be very diverse. The technologies we develop—the key is that these are funneling technologies. They take diverse feedstock and make it into a precise product called jet fuel.
Kristin Hayes: What are some of the feedstocks that these biorefineries are working with?
Zia Abdullah: The technologies that we have developed, in principle, can take any renewable feedstock and convert it into sustainable aviation fuel. You have woody biomass, such as purpose-grown wood. You can have beetle-infested biomass on the West Coast that has to be gotten rid of because it causes forest fires. You can have herbaceous biomass that you can grow for the purpose of making fuel. You can have municipal solid wastes that are landfilled, and you can even have wet waste such as sludges from farms, from the food industry. You can have sludges from wastewater treatment plants that can all be converted to SAF. We shouldn't forget algae, and we shouldn't forget carbon dioxide.
The Oak Ridge National Laboratory, which is also a Department of Energy (DOE) lab, has published a study called the Billion-Ton Report. This study concludes that the United States can sustainably produce over a billion tons of feedstock annually. Most of this feedstock can be converted to sustainable aviation fuel.
Kristin Hayes: How has the production and use of sustainable aviation fuels grown in recent years? Maybe you can give us a flavor of how much is in use now, and also some sense of what the trajectory looks like. You mentioned that there's quite a bit of potential, but do you see that translating into use as well?
Zia Abdullah: At present, we don't make a lot of fuel. We make about four and a half million gallons in the United States, and most of this is produced through a process called HEFA, which stands for hydrotreatment of esters and fatty acids. The feedstock for this are vegetable oils or waste oils, or fats and greases from animal rendering operations as feed.
This process is relatively straightforward and refineries can convert that into fuel. Currently, sustainable aviation fuel is being produced by World Energy in the refinery in Paramount, California, near Los Angeles, and Neste also imports sustainable aviation fuel into California from Singapore. Gevo has a production facility in Texas.
The Biden administration has directed industry and the federal government agencies through an executive order last September to work together to reduce greenhouse gas emissions from commercial aviation by 20 percent by 2030 and to completely decarbonize aviation by 2050.
In response to that, there was a memorandum of understanding between the Department of Energy, Department of Transportation, Department of Agriculture (USDA), and the Federal Aviation Administration (FAA) that formalized these greenhouse gas reductions into gallons of fuel. This came up to three billion gallons of sustainable aviation fuel production by 2030 and 35 billion gallons by 2050. This is called the Sustainable Aviation Fuel Grand Challenge, and we are all excited about this and very motivated to work on it.
Kristin Hayes: That's great. How much are we producing now in terms of that gallon equivalent?
Zia Abdullah: Four-and-a-half million. So, you can imagine that we have to go from four-and-a-half million today to three billion in eight years.
Kristin Hayes: There's a lot of growth needed. That's a great lead-in, actually, to the next question. What sort of strategies is the research community—whether it's at NREL, within the broader academic community, or within industry or other players—what sort of strategies is that community employing to help expand that supply in the timeframe that you've been talking about?
Zia Abdullah: The first pillar of the strategy is compatibility of fuel. Airplanes that are flying today will still likely be flying in 2030, and airplanes that are being sold today will most likely be flying in 2050. This means the sustainable aviation fuel that we make must be absolutely identical from a molecular perspective to the Jet A fuel that these airplanes use today, so that the current fleet can use it safely. As we all agree that safety is number one, there cannot be any compromises with respect to safety. Fuel is a big part of safety, so we have to make sure that the fuel we make is 100 percent identical to Jet A and must be a 100 percent drop-in. That's number one.
Second is feedstock. The United States already has the capability to make enough feedstock, but it's very diverse. The challenge is, How do you develop technologies and biorefineries that take this very diverse feedstock and make it into a homogeneous, precise fuel? That's part of our strategy, and how do we do it?
We do it through coalition, so that means that national labs, universities, industry—we all work together very actively. We work across agencies. The DOE, USDA, FAA, NASA are all working together; and then cross-industry, so that means that you have to work across the entire value chain, from feedstock suppliers to people who gather feedstock and then refine it. Very important partners are petroleum companies because they already know how to make the fuel and deliver it safely. This is all done through public-private partnerships.
Kristin Hayes: It definitely strikes me that those public-private partnerships between agencies, between government and industry—I can see how they'd be critical in expanding the use of these fuels. Can you say a little bit more about the work NREL or these other government institutions is doing with companies, either those responsible for building and operating the planes or those producing and refining fuels?
Zia Abdullah: You're absolutely correct. Public-private partnerships are very important, and the Department of Energy recognizes this. The Bioenergy Technologies Office (BETO) is an office in the Department of Energy that now issues annual funding opportunity announcements (FOAs). They provide grants to industry to work with technology partners like national labs and others to methodically reduce risk and scale up novel technologies to make sustainable aviation fuel. So the Bioenergy Technologies Office is helping with these public-private partnerships.
I can give you a really good example of this at NREL. NREL has a partnership with Alder Fuels. Alder Fuels and DOE are jointly funding technologies to make sustainable aviation fuel from very broad feedstocks ranging from woody biomass to actually wet wastes.
Alder is de-risking and scaling up these technologies.
Another example that we have recently had is with a company by the name of Sapphire Renewables. This company is working on producing sugars from corn store in the Midwest, and these sugars are then converted to ethanol through fermentation. Then the ethanol can be upgraded to sustainable aviation fuel in partnership with a company that was also DOE-funded. The name of that company is LanzaTech. This was a company that came out of research that was done at the Pacific Northwest National Lab through DOE funding. So public-private partnerships are critical in success.
Kristin Hayes: I want to follow up on the goals that the Biden administration has set in terms of the amount of sustainable aviation fuels available. You mentioned that there are gallon-level targets for 2030 and for 2050, but in other conversations the administration has set price targets, for example for hydrogen, or other things where driving down the cost of those technologies is critical to their adoption. Are there price targets in mind for these sustainable aviation fuels? Are they competitive right now, and the challenges are about scaling them up in terms of production? How do you see the economics of this playing out?
Zia Abdullah: I'll be very honest with you. If one does not take into account the societal cost of carbon dioxide in the atmosphere leading to climate change, it would be very difficult for sustainable aviation fuel to compete with fossil Jet A. When you look at fossil Jet A, you take crude oil out of the ground, you distill it, and you make aviation fuel and sell it. If you make a biofuel, you have to go and grow biomass, harvest it, convert it through much more complex processes, and then make fuel out of it. It will always be more expensive.
Having said that, cost is still very important. We understand that if we make fuel where the cost is very high, we'll never meet the gallon targets. In all of these technologies that we are developing, we strive to make fuels at the lowest cost that we can.
Then there is going to have to be support from policy where airlines and other industries will be incentivized to use sustainable aviation fuel. A very good example of policy is the Low Carbon Fuel Standard (LCFS) in California, and it is because of LCFS that most of the sustainable aviation fuel right now is going to California because the airlines find that they can take advantage of that, and they can decarbonize their flights and also get some benefit from LCFS. Having said that, the airlines are very cognizant of the greenhouse gas impact of their operations, so they're giving us a lot of leeway, and they're incentivized, and they want to work with us. If the fuel is even a little bit more expensive, they're still receptive to using the fuels.
Kristin Hayes: That's really good to know. In your view, what are the biggest challenges that the research community at NREL or elsewhere faces in meeting these lofty targets related to the use of these fuels? What do you see as the hurdles to overcome?
Zia Abdullah: If we are at four-and-a-half million gallons today, and we have to get to three billion gallons in eight years, we have to build production scale very quickly. We have to mobilize across the value chain. At least for 30 billion gallons, we have to make 600 million tons of feedstock: grow it and harvest it and process it. We have to develop new value chains. We have to deal with diversity. We have to have new conversion pathways that get approved.
We are starting a whole new industry in the United States. This is really exciting, because this will create a huge number of new jobs and help the GDP of the United States in a way that's beneficial to our climate. It's not going to be easy. There's going to be a lot of work, but I think that the positives far out with the negatives.
Kristin Hayes: It's the mobilization of the biochemical processes themselves, combined with training a new workforce, combined with actually siting new facilities.
Is that part of this as well—are there different kind of refineries and things that will be needed for these fuels? I want to emphasize, as you said, that there's an opportunity here, particularly if the feedstocks—unlike some of the global market challenges that we have with oil markets, for example—are coming from the United States. This can really be an opportunity for the United States to home-grow an industry. Is that the case?
Zia Abdullah: Absolutely. The United States has the capability to grow this biomass. I think that we are going to develop a new industry, but we have to take advantage of people who are already in adjacent areas.
For example, if you look at the forest-products companies of the farming community—we must engage with them to grow feedstock because they know how to do it. We don't have to reinvent the wheel and make expensive mistakes. Then, when we get on the other end, we look at fuel delivery to airports. Safe production of finished fuel. We have to engage the petroleum industry in that because they already know how to do it, and they know how to do it safely and reliably. We are going to have to develop a new industry, but it has to be done in a way that engages in a very positive way with existing industries that already work on the fossil side or on the farming side and get them to buy into this new vision and be leaders. There's a huge opportunity. Even for the petroleum industry, there are huge opportunities for reinventing themselves.
Kristin Hayes: Hearkening back to my somewhat odd comment at the beginning, I am really curious: will passengers know if they're flying on planes that are fueled by sustainable aviation fuels? Probably not, because the whole goal is to develop fuels that are so similar in terms of their properties that they can seamlessly plug into the existing aviation infrastructure that we have, but will it change the flying experience in any way? Are we going to smell french fries on board?
Zia Abdullah: I'm sorry to disappoint you, but there's going to be no wonderful aroma of french fries on your next flight. The fuel is going to be identical to Jet A so there'll be no changes at all.
Kristin Hayes: Fair enough. I will have to settle for the smell of warm rolls coming from the back of the planes. Good to know.
Well, this has been really interesting. I appreciate you taking the time to talk with me. I did want to close with Top of the Stack. Perhaps you've heard of this type of feature before, but, basically, we're looking for you to recommend any other good content that you might like. It can be on this topic. It can be of any medium; it could be on other topics. Something you'd want to share with our listeners as they continue to learn about these issues. So what's on the top of your stack?
Zia Abdullah: One topic that we did not cover in our conversation that has a lot of interest in Europe—and the interest in the United States also is growing—is the concept of eFuels. That means to make fuels and products from carbon dioxide from the atmosphere.
The idea is to capture carbon dioxide from industry-point sources, so if you have a fermentation plant or an industry-waste gas stack or you capture it directly from the air—these are DAC facilities, direct air capture facilities—and then use renewable electricity from wind or solar to actually convert the carbon dioxide through a process called reduction into some intermediate chemical then that can be further upgraded into a fuel such as a sustainable aviation fuel or a chemical. This is really important because we use carbon in our economy all the time.
Everything that we use from plastics to polymers has carbon in it. The idea is not to get rid of carbon. We would still use carbon, but we would create a sustainable circular carbon economy. That means that we would still use carbon to make fuels and products, but recycle this carbon from the atmosphere and upgrade it, rather than extracting the carbon like we do right now from the ground as crude oil and then disposing of it in the atmosphere. This circular carbon economy is really important and may be of interest to your listeners.
Then one question that people have with this is cost. How much would the final fuel cost or the chemical cost be, and what should be the reasonable cost of capturing carbon dioxide and electricity and using electricity to make these processes—what would the economics be? Are these processes ever going to be viable?
I've been reading this really interesting paper in volume 14 of the journal Energy and Environmental Science, and this was by my colleagues here at NREL—Zhe Huang, Gary Grim, Josh Schaidle, and Ling Tao. The title of the paper is “The Economic Outlook for Converting CO2 and Electrons to Molecules.” They've done a comprehensive analysis of many technologies and promising products that can be made in the near, mid, and long term. This is exciting because this study shows that at a contemporary cost of three cents per kilowatt-hour for electricity and about $20 a ton for carbon dioxide, there can be several products that are used in our society already that can be made from carbon dioxide.
If that is the case, then what really excites me is that we are on the cusp of a circular carbon economy, and, hopefully, in the near future we'll be able to use atmospheric carbon dioxide rather than having to pull carbon out from the ground. I think that this is a very positive and optimistic way to look at the future.
Kristin Hayes: Fantastic. That's a great recommendation. We'll make sure to put a link to that on the website.
This has been great. Thank you again for taking the time. I hope we can stay in touch about these many developments that are obviously coming down the pipe.
Zia Abdullah: It's a pleasure talking to you, Kristin. Thank you very much for this opportunity.
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