Erik Ringle, National Renewable Energy Laboratory: Well, hello, everyone, and welcome to today's webinar, “Sustainable Aviation Fuel and U.S. Airport Infrastructure.” I'm Erik Ringle, from the National Renewable Energy Lab. Before I go over our agenda today, I'd like to cover a few housekeeping items just so you know how you can participate in today's event.  

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The webinar today will cover three items. First, we will hear from Alicia Lindauer and Zia Haq from the U.S. Department of Energy's Bioenergy Technologies Office, who will contextualize today's topic on sustainable aviation fuel and introduce today's main speakers, Kristi Moriarty and Derek Vardon. Kristi Moriarty will then cover key points on sustainable aviation fuel infrastructure, and finally, we'll hear from Derek Vardon about the production and approval process of sustainable aviation fuel. Okay, and with that, I will hand it off to Alicia Lindauer to kick things off for us. Alicia?

Alicia Lindauer, Bioenergy Technologies Office: Great. Thank you so much, Erik, and thank you to everybody who has joined us today. So, my name is Alicia Lindauer. I am a technology manager with the Department of Energy's Bioenergy Technologies Office, and I oversee the Office of Sustainability and Strategic Analysis activities. The Bioenergy Technologies Office is focused on enabling innovative technologies to produce bioenergy and bioproducts from both biomass and waste resources.

Today's webinar is focused on work that we're doing in the area of sustainable aviation fuel, which is also known as SAF. So, it's [inaudible] context. Worldwide aviation accounts for approximately 2% of all human-made carbon dioxide emissions, and it accounts for about 12% of our transportation sector carbon dioxide emissions. Many airports and airlines right now are considering alternative fuel options to help meet their environmental and sustainability goals and mandates, and the Department of Energy is working to enable this transition to sustainable aviation fuels that are made from biomass or waste resources. So today you'll hear from Kristi Moriarty and Derek Vardon, who are both scientists at the National Renewable Energy Laboratory.

Kristi will be speaking first. She will be reviewing recently completed analysis that considered how sustainable aviation fuel can be delivered to airports. Kristi is a senior engineer at the National Renewable Energy Laboratory, and over the past 17 years, she has authored over 60 technical papers covering all aspects of bioenergy from feedstock supply through end use. She is an expert at both the fuel supply chain and biofuel compatibility with infrastructure. That work focuses on materials compatibility and meeting a patchwork of requirements that are necessary to introduce new fuels into the market.

After Kristi speaks, you'll hear from Derek Vardon. He's going to be giving an in-depth overview of SAF, and he'll cover some recent technology advancements. Derek is a senior research engineer and a project team lead at NREL. He is working to decarbonize aviation and heavy-duty ground transportation with low-cost and low-net-carbon fuels that are producing biomass and waste. He is an author of over 30 peer-reviewed scientific publications on biofuels and biobased chemicals.

He's an inventor on multiple patents—both pending and issued—and he's an affiliate faculty member at the Department of Chemistry at the Colorado School of Mines. Derek is most passionate when he's working to get technology out of the lab and into the marketplace, working with interdisciplinary teams that leverage national laboratory, academic, and industry capabilities to address critical technical barriers for sustainable transportation. So, again, I thank you all for joining us today. I'm going to now turn things over to Zia Haq. He is the lead analyst with the Bioenergy Technologies Office, and he oversees a lot of our sustainable aviation fuels work.

Zia Haq, Bioenergy Technologies Office: Thank you, Alicia, and thank you for all the participants. Hopefully you can hear us, and let us know if you have any issues—any technical issues. So DOE is, of course, very committed to developing innovative pathways for sustainable aviation fuels, and we are working on a variety of different feedstocks such as biomass, algae, wet waste feedstocks, and carbon dioxide. We are also working on scale-up of these technologies, and we hope that you are aware of the latest funding opportunity announcement, which has closed—concept papers have closed—but we hope to make awards on that announcement in September of this year.

We are working very closely with the U.S. Department of Agriculture and Federal Aviation Administration via an interagency working group to commercialize sustainable aviation fuel conversion technologies and to bring their cost down. And USDA, of course, has a critical role to play to develop new feedstocks, and FAA is helping with the international negotiations at IKO and with ASCENT funding, and with ASTM certification, and with outreach via CAAFI. We hope to bring other agencies into this initiative in the future. We're also monitoring several legislative initiatives that are going on in Congress and at the state level. As you may know, Representative Julia Brownley of California announced a Sustainable Aviation Fuel Act, and various other versions of that act are going through the process.

There's also considerable interest in international collaborations, and we've heard from several countries including India, Canada, European Union, Chile, and others who are interested in collaborating with the U.S. on developing sustainable aviation fuels. So, this is an area that we hope will become more relevant in the coming months. So with that, I'm going to turn it over to Kristi, and Kristi, let's hear about airport infrastructure needs. Thank you.

Kristi Moriarty, National Renewable Energy Laboratory: Great. Good morning or good afternoon, depending on where you are. Next slide.

So, just in terms of what I'm going to cover. As Alicia said, we published a report in February of this year on the U.S. market and infrastructure and looking at where the fuels might be blended, and jet fuel quality and the ASTM standards really drive a lot of the thought process around that. So, we'll just go over what those options look like and what might make most sense in some of the terminal operations' regulations—and there's a link to that report at the end of these slides. Next slide.

So, the International Civil Aviation Organization defines sustainable aviation fuel—SAF—as a fuel that achieves a net carbon greenhouse gas reduction in emissions and respects the biodiversity and the ecosystems from which these feedstocks are drawn, and where the fields were produced, and impacting social and economic development in a positive way, and ICAO set the jet fuel baseline value as 89 grams of carbon dioxide equivalent per megajoule. And one of DOE's labs—Argonne National Laboratory—has the GREET model, which analyzes that data and comes up with what the relative values of emissions might be from particular feedstocks and pathways to produce different fuels, and they found that the range for SAF fell between 5 and nearly 66 carbon dioxide equivalent per megajoule, and that depended on feedstock and technology. And just so you're aware, that higher end was for corn-based ethanol being converted to jet fuel, which probably isn't the most likely pathway. But in all instances, it was lower than that jet fuel baseline. Next slide.

As Alicia said, aviation worldwide accounts for 2% of carbon dioxide equivalent emissions, or 12% of transportation emissions, and ICAO adopted the CORSIA scheme in 2016, and that's just coming into effect with flights between the green countries on that map there, and in 2027 amongst the flights between blue countries and green countries, and the yellow countries are exempt. And then, the aviation industry as a whole has aspirational goal of reducing carbon emissions by 50% on 2005 levels through to 2050, and SAF presents a near-term opportunity to meet these schemes and goals. Next slide.

So, this comes from the report, and certainly not just in the U.S. but also across the world, we're seeing growth in both jet fuel use and enplanements, which is an example of a person boarding a flight. Obviously, there was a big fall-off in 2020, but I think we'll make it—data from this year—we'll see a recovery. Now, enplanements fell more than jet fuel use, and that's because the federal government requires a minimal level of service of flights going to different places. So, when the pandemic was first occurring, there were certainly flights going that maybe had 150 seats, but maybe 10 people on them. So, we'll wait and see what the rebound looks like that, but I think, over future time, we can expect there to be more travel by air. Next slide.

While 2020 was a difficult year for conventional jet fuels, a bright spot for sustainable aviation fuel, as you'll see here, nearly doubled between 2019 and 2020. And while the Energy Information Agency doesn’t put out production or consumption numbers for fuel—that's of the smaller volume—we were able to estimate this from the EPA's Renewable Fuel Standard public data just to get an idea of what the market in the U.S. might be at this time. Next slide.

So, what airports are using sustainable aviation fuel in the U.S.? LAX has been doing it since 2016, and then more recently, late in 2020, at San Francisco International Airport and Ontario International Airport—which also in California, not Canada—and then, most recently, last month, a general aviation airport at high altitude in beautiful Telluride, Colorado, is the latest in using this. And we do expect, in the near-term future that the majority of the stock production would go to California due to the Low Carbon Fuel Standard, but there's many other regions and airports that are interested in using this fuel, and there's a lot of steps that you can take to prepare for when there's more stock available. Next slide.

So, I'm sure we're all very grateful for jet fuel quality. Of course, on highways, transportation fuels are checked for quality as well, but jet fuel quality differs in that every time it moves across the supply chain, it is tested to make sure it meets the relevant ASTM standards prior to being used in aircraft. And when the fuel is produced at the refinery, it receives the Refinery Certificate of Quality, which is a traceability document—32-point test with a batch number—and as it moves across the supply chain, certified third-party laboratories do the testing to make sure that all of the criteria's met and it's a Certificate of Analysis that's generated. And it's recommended to do similar documentation for neat SAF or if it's produced as a standalone plant, and then, certainly, when it's blended with SAF, that COA would be generated. Next slide.

Conventional Jet A meets ASTM D1655, where SAF, when it's first produced, would meet ASTM D7566. And ASTM, over time, has approved seven SAF production pathways, and I'm sure we'll continue to see more technology pathways approved over time. And the percent of SAF that's allowable to be blended with Jet A is either 10% or 50% at this time as determined by the pathway. So, when SAF and Jet A are blended, tested, and meet all the relevant ASTM requirements, then that blend is designated as ASTM D1655. And what that means is it's a fully fungible drop-in fuel so, it's indistinguishable from the conventional fuel it's replacing—in this case, Jet A—and that means it can be used in existing aircraft and infrastructure and travel by pipeline. Next slide.

When we consider airport infrastructure, large commercial airports are generally going to have a pipeline and receive the majority of their fuel by pipeline. They might supplement by truck deliveries if they have the ability to receive by truck when the pipeline's at capacity on really busy times—like maybe July 4th or Christmas or some of those other busier times—whereas a smaller airport or general aviation airports are more likely to receive their fuel by truck. And airports have the tank farm that's located either within the airport footprint or nearby that has the ability to receive fuel by pipeline or truck, and also has equipment for detecting and preventing and containing any releases, as well as dispensing the fuel either to trucks that refill the aircraft or a fuel hydrant system, which is pipelines running underneath the gates. Tank farms are typically sized for the busiest weeks of the year—say, in Phoenix when it's baseball spring training and they got a lot more tourists than normal—and also, they're designed to accommodate future growth. And in some of the data that NREL collected, it looked like it was pretty typical for an airport to have 4–6 days of fuel use on hand.

Now, while the airport owns the tank farm, they usually lease it out to airline fuel consortiums, which is all the airlines at the airport that pull together their resources to source fuels from various producers and share the infrastructure to ensure that they can get all the fuel that's needed for all the different flights. And then, the airline fuel consortium typically hires a third party to operate the fuel tank farm in that process of getting and receiving fuel. Next slide.

So, in terms of fuel logistics and how fuel moves, conventional Jet A—whether produced at the U.S. refinery or imported—will get all the fuel quality check, and then will typically travel by pipeline—sometimes by barge—to a fuel terminal where it's stored, and then ultimately delivered by truck or pipeline to an airport. Biofuels, certainly when they're low volume, tend to travel by truck or rail and then either pass through a transmodal facility or directly onto a terminal if they can receive fuel by those methods. That's where they're blended in the case of, say, on-highway transportation fuel—like ethanol and blendstock for gasoline—and in this case, fuel could be blended at the terminal—the SAF and the Jet A—ultimately for delivery to the end user. In the case of what's going on right now, I would say Los Angeles International Airport—special case. They happen to be located by World Energy, which is the sole existing commercial SAF producer within the U.S., and they bring in the Jet A to their facility, blend it, certify it as an ASTM D1655, and it comes by truck to LAX.

In the case of San Francisco Airport, they're receiving fuel by ship. The Jet A and SAF are blended at the terminal, and it's delivered by pipeline to the airport. For Telluride, they receive all their fuel by truck, so that's how the SAF is coming in to that airport. Next slide.

So, when we're considering where to do the blending, it's first important to note that there's two places in which you could produce SAF. If SAF is produced or coprocessed at the existing petroleum refinery, the upgrade to the infrastructure and a certification of the fuel occurs at the refinery, and then it's just business as usual down across the supply chain and onto the airport, and no changes would be necessary there. We anticipate, initially, a lot of the sustainable aviation fuel will be produced at standalone plants, so it has to be blended somewhere prior to its use in aircraft. Neat SAF—so, that'd be 100% SAF—would not be able to travel by pipeline per current federal regulations. Perhaps that might change over time, but currently, today, it cannot travel that way.

So, NREL considered a number of different locations for where SAF and Jet A could be blended, and this included terminals, airports, refineries, and green- or brownfield sites. And looking at all these, I'd say the conclusion up front is terminals make the most sense because they already have existing infrastructure that's familiar with blending fuels because they do it all the time. And just that—the fuel quality standards dictate that it should be done upstream of the airport. Next slide.

So, there's a couple of options for blending at the terminal, and this is going to depend on the end user's preferences, perhaps the infrastructure at the terminal, for what might make sense in different areas and serving different airports. But one potential way is to store SAF in one tank, Jet A in another, and put the blend into a third tank, test it, make sure that it's meeting all the ASTM standards, and designating it as the ASTM D1655, and then injecting it into the pipeline or loading it onto trucks for delivery to their airport for use. Next slide.

Another option that might work as well is to offload the SAF directly into an existing Jet A tank that is set up with a mixer and do the blending within the tank, and then, once again, test and certify it. And this option just probably would require a little bit more software in making sure, with the accounting, that you never exceed the allowable level of the percentage of SAF that's blended. But same thing—it would go into the pipeline, it would be loaded to a truck for delivery to airports. Next slide.

A third option that came up is you could potentially, at a terminal, store Jet A and SAF separately, inject them into the pipeline—which has turbulent flow—where they would be blended; however, that would be establishing the first instance of the SAF blend as the D1655 at the airport, which isn't really desirable, because you might need more off-spec fuel tank at an airport. And also, you know, you're hoping there's that turbulent flow in the pipeline, but there's a very narrow range of fuel properties, and what's coming from the terminal needs to match what's at the airport. So, that's a little bit riskier than options one and two that I just showed. Next slide.

So, what certainly came up is, "Why not blend at the airport?" And certainly, that's possible, but again, it's not the ideal location because that would be the first instance of establishing SAF as a fuel—blended fuel that could be used in the aircraft. Also, the airport infrastructure would need to be upgraded. You're going to be adding blending equipment. You're going to need more storage for off-spec fuel. There's software and potentially more staff that you need, and you also have to consider the traffic impact to your airport as SAF would be coming in by truck, and what would that mean? You're already constrained with traffic at the airport, but that's just another consideration. Also, the tank farm insurance would be impacted because blending adds a little bit more risk to the activities that would be occurring at that facility. Next slide.

Another idea that had come up as a potential place to blend is at the refinery. The reasons that that probably doesn't make the most sense is refineries are not set up to receive a third-party fuel, particularly by truck or rail. Most refineries aren't going to have rail. And then, also, refinery storage is smaller than what you would find at a terminal, because it's sized for the refinery capacity, and certainly, if you introduce a new fuel into the jet tank at the refinery, you would have to do that 32-point test again and recertify that fuel batch. And while it's possible to set up a new site for blending—a greenfield or brownfield site—the reason that that option isn't ideal is because of the significant investment you would have to make to put all the equipment in there when the terminal already has that equipment available for lease. And also, the permitting time for a facility like that—and certainly, the ability to tie into a pipeline—would expect it to be very lengthy. Next slide.

So, just to make it clear, if the blending is done at a terminal, it's business as usual at the airport. The fuel's not stored separately. It's going to be stored in the same way and dispensed to the aircraft as it's done today, and no investment would happen at the airport. The investment would happen at the terminal. Next slide.

So, when this blended fuel comes into the airport, it's not going to be directed towards a particular airline or flight—especially with a fuel hydrant system. You just—once it's in that system, it's just going to the flights as needed as they're being turned around to go take off again. So, all airlines at the airport would need to be in agreement for SAF use, and then, only those airlines that are purchasing the SAF—or maybe in some instances, corporations with received credits—and on the right here, you see from Rocky Mountain Institute what a scheme like that might look like for accounting purposes and who gets credit for purchasing the fuel and receives that carbon-reduction value. Next slide.

So, some stuff that airports could consider today for the future and looking at bringing SAF to their airports is getting together with the airline fuel consortium and the fixed-space operator, and then finding out who's supplying your fuel. Is it a terminal? And is it multiple terminals? And then, find out, how can they receive fuel. Is it by rail? Pipeline? Truck? Ship? And if they can't receive by those ways, what would it take for them to be able to do that? And then, just identifying what equipment needs to be upgraded in order to bring SAF into the airport. Next slide.

So, if we look at terminals as the place to do the blending, they're owned by a variety of companies like oil and refinery companies—maybe a Shell, Exxon Mobil, Marathon, or pipeline companies like Kinder Morgan, Magellan, or Buckeye, or some other mid-stream companies—and they make their money by leasing out the equipment and receiving the fuel, storing it, and then dispensing it by pipeline or to truck offloading racks. Certainly, to add SAF at any terminal, there's going to be some cost. Generally, you're going to be able to lease existing tanks or tanks—whatever tankage is needed to do that. However, there's going to have to be some dedicated lines of pump. Say SAF is coming in by rail. Well, ethanol's probably also coming in by rail and we're certainly not going to put ethanol and SAF through the same lines because we don't want to have any contamination. So, you know, each terminal's going to have different things that need to be done to accommodate this, but that's not going to be a limiting factor in getting SAF out there. Next slide.

In terms of regulations, it was at least quite interesting to me—usually, these larger, aboveground fuel storage tank systems are regulated by EPA. Airport tank farms are the rare instance where they are not. However, states regulate them and tend to follow the same EPA laws, which are from the Stormwater Prevention Act, Clean Water Act, Clean Air Act, and just making sure it's done in a safe and environmental way. So, terminals are able to add SAF even if they were adding new tanks to accommodate SAF, which it's not anticipated to need to do that. It wouldn't impact their EPA operating permit. And the fuel hydrant systems—other airports that have them—are regulated by the EPA. So, that's just a really short little look, mostly at the federal level, on regulations. Certainly, you would need to inform your regulators that you're going to be bringing in this new blended fuel. Next slide.

And these are just some links to the report where most of this information was drawn from. Also, recently BETO and NREL staff did analysis looking at production tax credit versus an investment tax credit and how that might impact production, which Derek's about to talk about. A link to CAAFI and IACO and ASCENT, which Zia mentioned. And thank you. We're always happy to take on any more questions in this area, and I'd like to turn it over to Derek.

Derek Vardon, National Renewable Energy Laboratory: Okay. Thank you, Kristi. And so, next, I'll be diving in a little bit deeper into the technical pathways for producing SAF from biomass and waste carbon sources. Next slide, please.

So, I'll be touching more from a production basis, a lot of the motivation to decarbonize aviation sector with sustainable aviation fuel. I'll be touching on what makes SAF distinct from other biofuels used for ground transportation, as well as discussing some of the new and emerging routes to produce SAF from both renewable and waste carbon feedstocks. Next slide, please.

And so, as many of the speakers today mentioned, there's a growing need for looking at low-carbon-intensity fuels for the aviation industry. Air travel is expected to nearly double and significantly rebound even with the impacts of COVID-19. And as our speakers mentioned, jet fuel currently makes up 8%–12% of transportation emissions that are expected to grow. Within the U.S., we currently consume roughly 26 billion gallons of jet fuel per year, and even with the rapid emergence of electrification for our light-duty and ground transportation, there still are significant technical challenges with looking at commercial flight with batteries, and it's roughly estimated that current state-of-the-art batteries store 2.5% of the energy density per mass of jet fuel, requiring significant advancement in energy storage technology for electrification. Next slide, please.

And in terms of the decarbonization commitments, as you can see on the chart on the right, a critical component of commercial aviation's decarbonization strategy is utilizing SAF to reduce the overall carbon footprint. When looking at carbon emissions, jet fuel combustion is one of the largest sources of the aviation industry, and the International Civil Aviation Organization has set the goal—50% reductions of carbon emissions by 2050, relative to 2005. And so, significant growth in SAF production must be achieved within this time frame to go from the currently 5 million gallons per year today to offset the 26 billion gallons per year consumed in the U.S. Next slide, please.

In terms of current technologies and pathways to produce SAF, the majority of SAF today is generated by hydroprocessing fats, oils, and greases, technically referred to as triglycerides, as shown in the molecule on the left-hand side of the illustration. When processed over a catalyst with hydrogen, renewable hydrocarbon fuels can be produced that can serve both the aviation and renewable diesel market, commonly referred to as hydroprocessed esters and fatty acids—or HEFA for short. HEFA does compete in the same markets as renewable diesel, with diesel consumption within the U.S. also estimated on the scale of 46 billion gallons per year. As you can see, with adoption of the Low Carbon Fuel Standard in California, there's been significant growth in the production of renewable fuels, including green diesel or HEFA-based renewable diesel. And U.S. refining capacity for HEFA has—there's been significant announcements in the last 2 years of estimates of four billion gallons per year of capacity coming online.

But a key component of producing sustainable aviation and fuel is avoiding competition with non-food resources. And so, for lipids in particular, that's been estimated at 1.7 billion gallons per year, requiring significant volumes of new SAF routes and new SAF feedstocks to come online in this time period as well. Next slide, please.

In terms of what SAF routes are currently coming online within the U.S.—as you can see, in 2020, there's been several major producers in the million-gallon-per-year facility capacity. And the source of this information is the website, which Kristi mentioned, and I would highly recommend listeners today to visit. It's an excellent resource for the latest trends, which I'm only trying to touch on briefly here. But, as we can see, within the next 3 years, significant volumes are anticipated to come online, with pathways that move beyond just the lipids and triglyceride HEFA feedstocks. These routes include lignocellulosic biomass, alcohols from industrial waste gases, as well as looking at municipal solid waste and forestry residues as carbon sources for fuel production. Next slide, please.

In terms of considering, now, what makes sustainable aviation fuel distinct from other biofuels and transportation fuels, a lot come into its chemical composition that can be broken down and considered in terms of the major hydrocarbon classes. So, I want to emphasize that jet fuel really is an impressive, engineered liquid energy carrier with safety, operability, and performance being core requirements for jet fuel. Jet fuel is unique from ground transportation gasoline and diesel in that it requires no residual oxygen or other heteroatoms—when you consider biofuels such as ethanol and biodiesel that both have significant quantities of oxygen. In addition, the carbon number of jet falls in between that of gasoline and diesel, mainly through historical purposes from the refining industry. But in order to ensure the safe standards, ASTM International has established a qualification process to ensure that any renewable jet fuel meets the same performance criteria for existing aircraft as it would for fossil jet fuel. So, it's identical regardless of fossil or renewable origin when blended at the specified limits. Next slide, please.

You know, apologies for the—I'm a chemistry buff myself, so I like to include a lot of structures here. When looking at jet fuel, it's comprised of four main hydrocarbon types—so those are molecules that contain only carbon and hydrogen. When looking at the structures of jet fuel, you have straight, branched, ring, and unsaturated ring structures, commonly referred to as paraffins, which their distribution's shown there on the bar chart on the right. When looking at the carbon number of jet fuel, as mentioned, it has higher carbon numbers than gasoline, but a lighter carbon number distribution than diesel fuel, with the average carbon chain length of C11. That matters when considering the ways to produce jet fuel renewably from smaller molecules or larger molecules in a conversion technology. Next slide, please.

As Kristi mentioned, extensive testing is required to certify jet fuel, and there are in-depth documentations listed below by ASTM International that I would reference viewers to look into more deeply if they would like to know more about the specifications. But, in general, jet fuel requires a very high-energy-density, low-temperature performance to avoid freezing at high altitude, and for safe handling, a minimum flashpoint for flammability, amongst other specifications listed in detail. And these are covered by both ASTM D1655 for conventional jet as well as D7566 for fossil jet containing synthesized hydrocarbons. Next slide, please.

In terms of the qualification process for new SAF routes, there is specific literature as well by ASTM detailed in D4054 that requires evaluating new SAF routes to the tiered testing, reporting, and validating process. Historically, as new SAF routes have come online, the process works through various stages of feedback and can require producers to supply over 100,000 gallons of jet fuel with a time period of 3 to 7 years. But, as this data has accumulated over time and performance of SAF and specific SAF molecules have become better understood, in 2020, ASTM recently announced a fast-track approval process, which limits sustainable aviation fuel blending at 10% but can greatly accelerate the process if the molecules are comparable to those found in fossil fuel. So, this was recently demonstrated in under a 2-year time frame with a new Annex A7 on elbow-based hydrocarbons, and the qualification process can be done with much smaller volumes and a lower cost in timetable relative to the conventional process as a trade-off of the lower blending limit. Next slide, please.

Diving in deeper now into the current seven approved ASTM annexes. They have very detailed specifications for each, and shown here on the right, I wanted to highlight some of the starting feedstocks for producing these renewable jet fuels. So, historically, Fischer–Tropsch process to produce syngas—which is a small carbon monoxide and hydrogen that get elongated, as shown here in blue—has been approved for both some of the straight-chain, paraffin, kerosene, as well as aromatics and annexes. Also, triglycerides and fatty acids are prevalent feedstocks, as mentioned earlier, that can go into similar approved pathways. And in a direct biological route, both farnesene and, recently, an algae-based botryococcene had been approved.

And then, certainly, there's been significant work in development around ethanol and isobutanol as starting alcohols for approval. There are also now several new SAF routes under active evaluation process by ASTM, and these include aqueous-phase sugars from biomass deconstruction, catalytic pyrolysis routes, and additional alcohol to jet routes that incorporate a wider array of hydrocarbon molecules to look at greater blending levels for sustainable aviation fuel. Next slide, please.

And in terms of emerging routes that are active in development within the Department of Energy, there are multiple technologies that can produce SAF-range fuels from biomass and waste carbon. Commonly, biomass is referred to as lignocellulose, which refers to both the lignin and the cellulosic portions of biomass that can be deconstructed into C5 and C6 sugars, furans, as well as lignin monomers that can be upgraded into jet fuel. In addition, there's been several bio-oil-based approaches with thermochemical technologies that deconstruct whole biomass into a mixture of oxygenates and trace hydrocarbons, with significant work going on within the Bioenergy Technologies Office program to demonstrate production of hydrocarbon-range molecules suitable for SAF with this pathway.

In addition, with advancements in biological processing with both engineered and natural occurring consortiums of microorganisms, there are a host of bio-based intermediate molecules ranging from acetone, butanol, and ethanol, all the way to pure hydrocarbon terpenes that can be upgraded further into jet-range molecules. And then, certainly, with the emergence of greater amounts of renewable electricity and strategies that look to upgrade CO2 in the value-added molecules, extensive work has been going on in electron-to-molecule approaches—whether that's power to liquids or electrochemical means—to further grow the carbon backbone from small carbon and oxygen molecules. Next slide.

And in terms of feedstock and availability—which I believe came up in the chat—certainly, the Department of Energy has done significant analysis of the potential carbon sources that could be used to produce SAF. When looking at just lignocellulosic biomass—whether that's from agricultural residues, forest trimmings, or dedicated bioenergy crops, considering still a one-third split of jet fuel to gasoline and diesel—which depends on the biomass and technology pathway—over 20 billion gallons per year of jet fuel energy potential can be accessed from these feedstocks. In addition, other waste carbon sources—such as animal manures, wastewater sludges, food waste, MSW, and industrial waste gas—offer another significant energy source—roughly half that of 10 billion gallons per year—again, with the caveat that all of these are feedstock- and pathway-dependent, and estimates will vary. But at least it does provide a rough estimate of the potential energy availability within the U.S. for biofuel production that is commensurate with jet fuel consumption. And certainly, from a broader standpoint, the production of SAF provides critical links to both agriculture, food security, and waste management practices, so there are opportunities for cross-sector benefits at the intersection of energy and environment. Next slide, please.

In terms of getting these technologies beyond a research and development level into the marketplace, there's significant ongoing work and its specific funding call mentioned on helping us scale up and de-risk the various production technologies for sustainable aviation fuel. These are commonly referred to as both the technology readiness level, but specific for SAF, also a fuel-readiness level, with more detailed references provided below on both. But the core concepts on each of these are moving from the proof of concept and validation of fuel properties all the way through the integration, scale-up, and de-risking in a stage-gate process to enable operation at commercial scale for emerging SAF pathways. And certainly, the lessons learned with cellulosic ground transportation biofuels can be readily applied as new SAF pathways are being actively worked on towards commercialization. Next slide, please.

And to help facilitate this process, as mentioned, jet fuel can also be considered a highly engineered liquid with very detailed fuel property specifications. And so, the Department of Energy program—as well as others sponsored by the FAA and National Jet Fuel Combustion Program—are bringing online low-volume analytical techniques that can help rapidly inform the development and iteration cycles for these new SAF pathways. These leverage the molecular structure-property relationships that can help determine how specific molecules produced from renewable resources can be blended or evaluated neat, and how various structure property relationships impact the final fuel properties to add benefits such as increased energy density, reduced sooting tendency, or improved cold weather performance through fuel property-structure design. Next slide, please.

But certainly, the questions often come up on both the cost and carbon footprint of new pathways to produce SAF. And so, DOE has been doing extensive process modeling looking at the various unit operations and technology configurations for existing and emerging SAF routes. This techno-economic modeling approach frequently incurs cost sensitivity analysis to understand what the key performance drivers are that impact final cost of sustainable aviation fuels. As highlighted in the bar chart below—adapted from a recent report by World Economic Forum and McKinsey—typically, the cost of renewable fuels can be broken down into three categories around capital expenses for equipment, operating and expenses, and a starting feedstock that is used to produce SAF. There's been extensive strategies actively in development to decrease the price, and this can include the use of waste materials, as mentioned earlier, symbiotic services—such as waste management—and strategic offtake agreements.

In terms of the operating expenses category, technology is continually improving to increase fuel yield and energy efficiency, and certainly, capital. A lot of work is ongoing to understand how new SAF pathways can leverage existing refinery infrastructure very similar to the HEFA-based process. And the carbon and RIN credits also can encourage optimization around reduced carbon intensity. Next slide, please.

And in terms of the latter point, extensive life cycle analysis can provide a framework for comparing different SAF routes and their carbon intensity relative to fossil jet fuel production. There's been several recent publications surveying the different SAF pathways that have a range of carbon intensity reductions from over 90% to above 50%. And typically, as similar to the fuel selling price, feedstock can be a significant impact on the overall carbon footprint of SAF, with opportunities to lower the carbon intensity further through diverting methane emissions from landfills, applying agricultural practices that offer soil carbon sink potential, and certainly, operating with improved energy efficiency, whether that's through incorporation of renewables such as renewable electricity or even alternative hydrogen sources such as renewable natural gas steam reforming or electrolysis. And collectively, these various strategies have been shown to enable low- to even negative-carbon-footprint sustainable aviation fuels when considering their fuel-to-fuel life cycle analysis. And so, last slide, please.

I hope we've given you a good overview of the technical pathways and infrastructure requirements for SAF. So, certainly, we'd like to thank everyone for their attention and I’m glad to turn it back over to Alicia for final closing comments.

Alicia: Great. Thank you so much, Derek, and thanks to Kristi for presenting today. So, we do have some time for questions. I know several have come in so, I'm going to read some of these off of the chat. But before I do, a number of questions did come in about whether slides would be available, so I did want to let you know we are recording this webinar, and so slides and the webinar broadcast will be available on the Bioenergy Technologies Office website in a couple of weeks. It just takes a little while for that to go, but they will be available.

Great. So, we have had some questions come in so, I will go ahead and start reading some of those off. So, the first question is, "Given the available feedstocks and manufacturing processes, what percent of total U.S. jet fuel could be sustainable aviation fuel by 2020, by 2030, other times in the future?"

Derek: Great. Yeah. I will—glad to field that question. So, as one of the comments in this slide mentioned, current jet fuel production from renewable resources is under 10 million gallons per year in the U.S., with a total demand of fossil jet fuel of 26 billion gallons per year. When looking at the available biomass and waste carbon that could be online by 2030, there is an energy potential equivalent of the fossil jet fuel demand, but getting the technologies online and production volumes to that scale certainly would be a significant scale-up and ramp-up of the current production capabilities.

The HEFA-based process—using fats, oils, and greases—that has a near term in the next 2 to 3 years, estimated capacity of four billion gallons per year coming online in the U.S., but that will also compete with the renewable diesel market as well, since it can—HEFA can serve both SAF and renewable diesel fuel requirements.

Alicia: Great. Thanks, Derek. Cool. We've had a few other ones come in. So, there's a couple about, kind of carbon. So, "How much carbon is produced when producing SAF, and what is—kind of from a bottom line—what is the real impact on CO2 emissions?"

Derek: Hmm.

Alicia: I think, Derek, you covered this a little bit when you were talking about the LCA work.

Derek: Yeah. I'll at least speak to the commercial route. So, with the HEFA process being the primary route for commercial SAF production, I believe the latest numbers have that at 18 megajoules equivalent—excuse me, 18 CO2 equivalents per megajoule—which is a significant reduction relative to fossil fuels being at roughly 85 CO2 equivalents per megajoule. So, there's been continuous work to get the carbon footprint of HEFA SAF further reduced, with the renewable hydrogen being a very near-term option to reduce the carbon footprint. And then, as indicated, a lot of the emerging pathways are looking to get that number even further reduced—whether that's through the feedstock production and cultivation process or through diverting carbon from landfills that may otherwise go on to methane emissions. So, I hope that frames the reduction potential for HEFA SAF, at least relative to fossil jet.

Alicia: Great. Thanks, Derek. So, there's a couple of questions that I think would be best answered by Kristi. "How does using a SAF blend affect engine performance or engine maintenance?"

Kristi: It's a fully fungible and drop-in fuel so, it's—you know, it's not going to impact those. It might burn a little bit cleaner. I'd like to follow-up on that question if I could have the email of the person who asked it. But, since it is a drop-in fuel, that performs in the same way as conventional Jet A. There should not be an impact.

Alicia: Well, great, Kristi, and I know that there is some work that we didn't cover today, but there's some work in our office looking at fuel properties that could potentially have a positive impact on engine performance. So, I know that there's at least some earlier-stage research looking at that question. Great. Kristi, another question for you on infrastructure. What are the barriers to using existing pipeline infrastructure if we get to a point of very high displacement volumes?

Kristi: The only real barrier today is the Federal Energy Regulatory Commission determines what fuels can travel by pipeline. Neat SAF currently cannot. It has to be blended. And as long as it's blended in the allowable amount with Jet A at the 10% or 50%—depending on pathway—it can travel by pipeline. But that's something that might require a little bit of research and work to enable the transportation of that fuel longer distances by pipeline than just from the blend from a terminal to an airport. But otherwise, I would say there's not many barriers. It's just thinking through the fuel quality standards with your particular airport scenario and what it takes to get it there.

Alicia: Great. Okay. I've got another question. "So, considering the current value of RINs and other credits, is it advantageous to use HEFA as renewable diesel, or is it more advantageous to use it as a sustainable aviation fuel?"

Kristi: I know, in terms of the renewable identification numbers as so much as the compliance mechanism for the Renewable Fuel Standard, the basis of the RINs is on energy content, and it's ever-so-slightly higher for renewable diesel compared with SAF. I'm not sure how that translates for the Low Carbon Fuel Standard in California, the level playing field. But it's very slight, and certainly we could provide those numbers to anyone who's interested.

Alicia: Cool. I've got one question. I think this might be our final question. I think this one is to both Kristi and Derek. "What is one action you would encourage today to increase SAF production and use?"

Kristi: Well, the analysis that I linked to on one of the slides points toward production tax credit, and certainly, that was afforded to on highway transportation fuels, which you saw them get up to where they're billions of gallons of use. So, that's certainly something that perhaps could be instituted by industry and Congress.

Derek: Yeah. And I think from a technical perspective, I think looking at SAF routes that are able to leverage more of existing infrastructure to help reduce the cost and timeline to market are impactful for near-term SAF adoption.

Alicia: Okay. Great. Thanks to both of you. So, I think in our final minute, I'll go ahead and wrap things up just to remind people—so, up here on the slide right now, you'll seen contact information for Kristi and Derek. So, if you had a question that we were not able to answer today, please, feel free to email either of them directly with your question, and I'm sure that they would be willing to get back to you on it.

Another just quick reminder—this webinar was recorded, so the recording of the webinar will be available on the BETO website within a couple of weeks. The slides will also be available. And with that, I just want to say thank you so much. We had really great attendance, more questions than we were able to answer today, but we really appreciate both Derek and Kristi and Zia for your presentations and comments today and for all the questions and attention from everybody who was able to join. So, thank you.

Derek: Thank you.

Alicia: Thank you.

Erik: Thank you, everyone.

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