Webinar on the GREET Fleet Footprint Calculator (Text Version)
This is a text version of the video for the GREET Fleet Footprint Calculator webinar presented on Jan. 7, 2013, by Andrew Burnham, Argonne National Laboratory.
COORDINATOR: Good afternoon and thank you for standing by. All participants will be able to listen only for the duration of today's conference. I would now like to turn the call over to Sandra Loi. You may begin.
SANDRA LOI: Thank you. This is Sandra Loi from NREL supporting the Clean Cities program. Thank you for joining us today for today's webinar. Today, we will be focused on the GREET Fleet Footprint Calculator.
And we have Andy Burnham from the Argonne National Lab who will do the webinar and walk you through the updated calculator, which recently went through an update.
He'll give you an introduction to the lifecycle analysis, do an overview of the tool, as well as explaining the features that have been recently added. We will host a question-and-answer session at the end of the webinar, so make notes as he goes along, and then we'll open up the lines at the end for those questions.
So I'm going to go ahead and introduce Andrew. Andrew, or Andy Burnham, has been a fuel and vehicles systems analyst at Argonne National Laboratories since 2004.
At Argonne, he's been performing lifecycle analysis to help updates of the Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation, or GREET, model.
In addition, he's helped develop tools and provide technical analysis regarding the energy use and emissions of alternative fuel and advanced vehicles for the Department of Energy's Clean Cities program.
He received his bachelor's degree in environmental engineering from Northwestern University, and his master's degree in transportation technology and policy from the University of California, Davis. Andy, you may begin.
ANDY BURNHAM: Thank you very much, Sandra. Thank you for everyone joining in on the webinar.
I am going to be talking about the modeling tools that we've developed for the Clean Cities program, specifically for Clean Cities coordinators but also stakeholders who are interested in looking at oil use and greenhouse gas emissions. I'll start off.
So the presentation will start with a little bit of background on Argonne and then talk about lifecycle analysis in the GREET model, and then do an introduction of the GREET Fleet Footprint Calculator, and then finally go through quick demos of the tool.
So Argonne, in brief—Argonne's been a national laboratory for more than 50 years. It's been doing research in nuclear energy, physics, basic sciences and so forth. It is managed by the University of Chicago, and Argonne in a joint venture with more than 3,000 employees in 5,000 facilities.
The facilities are like advanced photon research. So it's basically different tools for researchers around the country that can come and do basic science and national security research. What I work on is transportation issues. And I'm in the Center for Transportation Research.
We do some advanced battery development. Some of the work that was done to develop the Volt battery was done here, and there's—just announced within the last month or so—some more research dollars to push the development of the next generation of batteries for vehicle use.
Some of the other things that are there are the autonomy model, which is a model that does vehicle simulation, and the GREET model, which I'll talk about right now.
So getting into lifecycle analysis—well, one of the key things that is important is trying to address two of the major issues that we see for the Department of Energy in the transportation sector.
One is oil use and the impacts on energy security, and the second is greenhouse gas emissions and its impacts on climate change. So those are two of the major challenges.
Well, there are also two major approaches to address them—one being vehicle efficiency and then the next being new transportation fuels. But these are both areas that lifecycle analysis can help provide information on.
So this is a chart that many of you have seen as looking at production versus consumption in the U.S. that shows in the past and then projects out into the future. So back in the '80s, we crossed over where our production wasn't meeting the consumption. And even today, we're roughly around 50%.
It kind of goes up and down depending on and even with the spike of domestic oil from tobacco and shale and things like that. We're still importing 40% to 50% of our petroleum. So it's still a major security issue.
And the actual amount from the Gulf doesn't really—hasn't changed much in a while. It's about 25% of our imports.
So moving to greenhouse gas emissions, highway vehicles are a significant portion of the greenhouse gas emissions that are produced in the U.S. Roughly a third comes from the transportation sector.
Now when we drill down a little bit deeper, we see the light-duty and heavy-duty trucks are really the key players accounting for more than 80% of the greenhouse gas emissions from the transportation sector alone. So this is an area that we want to focus on specifically.
And that's the tools that we're developing. For Clean Cities, we're looking at really light-duty and heavy-duty vehicles. So what is lifecycle analysis? Well, it's a tool that helps transportation researchers examine petroleum use, greenhouse gas emissions, and other things.
It's also called well-to-wheel analysis or fuel cycle analysis. Really, the pioneering work was done in the '80s with the focus being on electric vehicles.
And so we come full circle 30 years later that there's still that interest in doing both lifecycle analysis, and obviously the vehicles are here today.
So when we are doing new studies, we look at new fuels: cellulosic ethanol, algae-based fuels. Things like that are currently being researched now.
New vehicle technology—so the plug-in hybrid—trying to understand some of the challenges of when you have both electricity and gasoline or another fuel on the vehicle. So those are some of the things that we look at when we're doing a lifecycle analysis.
Now at Argonne, we've developed a tool called the GREET model, and so from the left to right, it has two basic parts. From left to right, we see the fuel cycle, and what is the fuel cycle?
Well, it's getting all of the processes required to get the fuel from its initial stages, transform it into a useful product, and then get it to your vehicle. So it's kind of the well-to-pump stage. So as we see this first symbol, it's an oil barracks.
So you're drilling out raw crude, and then you transport it to a refinery, and then it's refined into different product. Let's say gasoline is the one we're interested in. Then you send it to a refueling station, and then finally you use it in the vehicle.
And when you use it in the vehicle, that's the pump-to-wheel stage. And so that's the well-to-pump plus pump-to-wheel and well-to-wheel. So there's lots of acronyms—lots of things like that. But I think the key thing that it's a lifecycle. It's looking at kind of the entire product.
So the other stage of the vehicle cycle that's going from top to bottom, and that's all of the processes required to build the vehicle.
So this can be important for new vehicle technologies like battery electric vehicles, the fuel cell vehicles that have materials that are much different or have different, basically, components that are much different than a conventional gasoline vehicle.
We went backwards there. So the GREET model, well, what does it do? Well, it estimates energy use, greenhouse gas emissions, and criteria pollutants. So when we look at total—when we look at energy use, you can look at both fossil and renewable energy.
So we calculate both of those, and we break fossil into coal and petroleum and natural gas. And then for the greenhouse gas emissions of concern, the primary ones for transportation are carbon dioxide, but also important are methane and nitrous oxide.
And then the criteria pollutants that we examine are volatile organic compounds: carbon monoxide, nitrogen oxide, sulfur oxide, particulate matter 10 microns and less, and then particulate matter 2.5 microns or less. And the GREET model can be found at this website below.
So I think Sandra said this presentation will be available online, so you'll be able to find the tool. And so this is a more complete tool than the GREET Fleet Footprint Calculator, which I'll talk about more. But it includes more than 100 fuel production pathways.
So we have these primary—feedstocks is what we call them—so petroleum or natural gas or even corn coal, things like that, that you need to transform into a product or a transportation fuel. So the darker red boxes are the actual fuel that we look at.
And we've added things, not just—we primarily focus on light-duty vehicles, but we also include aviation fuels and things like that. So we're trying to expand in the future for other interesting areas for transportation as well.
Now for vehicle technologies, we look at more than 80 different fleet vehicle and fuel combinations. So when we look at a conventional vehicle, we typically think of—it's a spark-ignited vehicle that uses gasoline, but you can also use a natural gas or ethanol in a spark-ignited engine.
For compression emission, we look at diesel and isotope diesel, biodiesel, those types of fuels. Obviously, electric vehicles, hybrids, and plug-ins are all part of the tool.
Now as I mentioned, for GREET 2, this is really the raw material. Recovery is the first stage when you try and look at the vehicle cycle, which is producing the vehicle.
So if you're getting, say, steel, you have to mine taconite ore, and then you will process that ore to make actual steel, like a roll of steel. And then you'll need to make a component. So you might make an engine block or a transmission.
Then you assemble all of those different components together, and then we think about end of life, the disposal and recycling of the vehicle, which can be especially important for battery technology and so forth. So what does this all mean when we put it together?
Well typically, the thought is you're looking at what's going on at your vehicle—what's coming out of your tailpipe. So this is greenhouse gas emissions. So we can look at some different vehicle technologies, and this is the pump-to-wheel stage or basically the vehicle operation.
And you see gasoline vehicles have significant emissions. When you compare it to like an electric vehicle—fuel cell vehicles, they have no emissions.
So it's especially important for alternative fuel vehicles in these advanced vehicles to look at this whole stage because when you add the well-to-pump, which is all of this upstream, all of the processes required to get the fuel to your vehicle, it changes the story significantly.
So an electric vehicle doesn't look as good as if you just considered the tailpipe emissions.
And then you have to bring the vehicle cycle together, and it's relatively the same but for, say, electric vehicles where you might have a battery replacement or something like that. It can become more important.
So this gives you a holistic approach when you look at greenhouse gas emissions, energy use, and so forth. So that's what the focus of the GREET model is. So what I wanted to really focus in on is the GREET Fleet Footprint Calculator.
So this tool was developed with the help of the Clean Cities program. The origins really of our work with Clean Cities started in basically 1998 where the Department of Energy and EPA co-sponsored Argonne to develop a tool called AirCred.
And this tool was just a Clean Cities coalition to estimate ozone precursor and carbon monoxide emission credits from alternative fuel vehicles, so basically criteria air pollutant emissions. And this is for use in state implementation plans.
Now that the emission standards for vehicles have become so much tighter, the incremental benefit of alternative fuel vehicles is not so great for criteria air pollutants just because really these vehicles are—even gasoline or diesel are extremely clean.
So the focus has moved towards petroleum use and greenhouse gas emissions. So that was the reason why we wanted to develop this tool. And so we've given data actually to FuelEconomy.gov.
If you ever go onto that website and want to compare the different vehicles, you can look at the petroleum use and greenhouse gas emission calculations there, and that's from the GREET model.
So what we wanted to do is—there was a gap, and there was a gap for medium- and heavy-duty vehicles as well as off-road equipment.
So we wanted to try and fill that gap by developing a spreadsheet-based tool to provide users with some tool that they can enter their own information and try and get that data for doing these types of footprint calculators.
And the reason why you don't really see anything like a FuelEconomy.gov for medium- or heavy-duty vehicles is because there isn't the regulatory program where you have a testing procedure to get a fuel economy for, say, a school bus or a transit bus or things like that.
There isn't that type of procedure. So what we have to do is use our own research data and use your own data to develop your footprint. The GREET Fleet tool is available for download. We just updated the model, as Sandra said, in late November.
And then the fuel, the vehicles that are included, not as many as there are in the actual GREET model , but it's a little bit—it's a simplified tool. It's not for people who want to get into really the nitty-gritty details.
It's more to try and get basically a good representation of the vehicles you have or potentially the vehicles that you're interested in purchasing. So it's not for research purposes. The vehicles we include are conventional gasoline and diesel. We have a diesel hybrid.
For the alternative fuels, we have B20 and B100, E85, compressed natural gas, liquefied natural gas, propane, electricity, and both gaseous and liquid hydrogen. Now we do allow the user to get into a little bit more detail than just picking a fuel.
You're able to simulate where does that fuel come from because it can really change the answer. So if you, depending on where you get the biodiesel—is it soy based? Is it from algae? Algae was one of the new things we added. Is it corn versus cellulosic?
For natural gas, we've done some research on shale gas. We added shale gas to the mix. And then we're able to change our electricity mix depending on where you are and what potential electricity you are using to refill, say, your vehicle.
But all of those things are important when doing these types of calculations. So we have those options available to the user. And the tools available at—basically it's at the same website as the GREET website. And you see that it is based off the public version of GREET.
So as the GREET model changes, we can simulate, try to update GREET Fleet to take into account those changes. And then, I think as we've mentioned to Sandra that some of the coordinators to try and download before you—before the webinar in case you wanted to get familiar with it.
We also have not just an Excel spreadsheet, but we also have an online version with a Java-based tool. It's to do again quick calculations—can be used that way to get nice online quick results.
If you want to get in some more detail, I would recommend doing the spreadsheet so you can save your results and go back to it and keep it in the future.
So I want to get into a few demos, and then potentially, I think we'll have time to get into the spreadsheet just to do a quick walkthrough and show you how to maneuver about. So the first demo is going to be comparing on-road vehicle technologies for potential acquisitions.
There's really—I think there are two ways that users can use the model or the tool. One is looking at what vehicles you have—so doing a footprint of the vehicles already in a fleet.
And then there's another way, which I'm going to show in this first demo—is looking at new vehicles that you might want to purchase, and compare the different options and see what the footprint is of, say, a natural gas transit bus versus a diesel transit bus or something like that.
So it gives you a way to look at different options—kind of like what FuelEconomy.gov is used for. So what do you need when you're using the GREET Fleet tool?
Well. when we're doing this kind of calculation for potential vehicle acquisitions, what you need to know or what you need to enter is how many vehicles are you interested in purchasing, the annual miles traveled that you project for the vehicles, and then the fuel economy.
So the tricky part for again medium/heavy-duty vehicles is that fuel economy value as we don't have a regulatory program to give us a set number for the transit bus or so forth.
We need to use existing information, or you need to speak with potentially the people who are if you're already in that approach where you wanted to talk to manufacturers or dealers and say roughly what is the fuel economy of the vehicle?
You can use that, punch it into the tool, and then get a rough estimate. It's better if you have your own data. We do include default data that was based on research we've done. But if you have your data, that's obviously the best thing to use.
So the first step I guess after selecting how you want to calculate—so the first step is—do you want to calculate with your fleet size, or do you want to just look at your fuel use?
So if we're going to choose option one here, we're going to choose for potential vehicle purchases and enter our fleet size, VMT, and fuel economy.
So here we enter—I'm doing some screen shots from the actual tool, and say we want to compare a diesel to a diesel hybrid to a B20 and a compressed natural gas vehicle. You enter, say, the number of vehicles, in this example, 20 vehicles here.
And then you go to the next payable. The next payable is your VMT. We also provide default data, but again, you want to put the data that your fleet—that's very important. If you're kind of—we changed the default from 30,000 miles per year to 50,000 miles. This is per bus mileage.
After entering that, we look at the fuel economy. And all the values are in miles per gallon—miles per gasoline gallon equivalent, so MPGGE. You might be using miles per diesel gallon, so that's just something to be careful with—that's how the values are entered in the model.
So here again, we might want to change those values depending on—you have, say, better data. The next step is getting into these kinds of assumptions on where the fuel is coming from. So if we wanted to change something for, say, the natural gas, we could choose a couple of options.
So for net—for CNG, we might look at North American natural gas. In some cases, you might be getting natural gas from a non–North American source. That would—that case would likely happen more for LNG if you're using LNG. That might happen. That might be more possible.
And then we also have a renewable natural gas option that's landfill gas. So that would be—so you'd just click in here and choose three.
Now if you're looking at North American natural gas and you wanted to look at conventional versus shale, we have just options here where you would just say, well, this is a national average value.
It's mostly conventional, but say you're in an area where you're getting mostly shale gas. You could zero out the conventional and have 100% shale, and then look at your results there. Now that's basically it. So that's—those are the main steps.
And then once you go through that, you'll get to the results, and what we see is petroleum use in barrels of oil and then greenhouse gas emissions in short tons. So this is in the same format as FuelEconomy.gov, the same format, the same thing.
So you get to look at, depending if you're looking at a lot of vehicles, you can look at them on a vehicle basis, or you can look at them on a fuel basis and see how much of the petroleum use and GHGs for each type. And then if you are interested in light-duty vehicles, you can use this tool.
There's like another category, and you could punch in that information as well if you wanted to do all of these calculations together. You can use the other category for a light-duty vehicle. Now the next demo is for doing an off-road. And this is just looking at basically a fleet's footprint.
So you already know you're looking at, say, the 2012 fuel use of some of your off-road equipment. So this is just a much even quicker approach to getting the numbers. So at the top of the sheet, there's this option on how do you want to calculate?
Do you want to do this future vehicles, or do you want to just do fuel use, which is basically the vehicles that you already have? But here, we're going to select option 2 and then go to table 5. We skipped to table 5.
In this demo, we're just going to look at forklifts with using diesel and then another forklift that's using electricity and then a gasoline air compressor. So it's as simple as entering the values into the spreadsheet for each of the different types.
We have added a few new types like the commercial turf mower and things like that, but you have to go into these areas. And then this is all in—this isn't in gasoline gallon equivalents. This is in the actual unit of fuel that you might be using.
So for gasoline, it's gallons of gasoline. For diesel, it's gallons of diesel. Biodiesel, and so forth, it's gallons of biodiesel. And then for electricity and some of the other ones, it's kilowatt hours. So the units are there that kind of show you.
And then at the bottom of the table, it'll give you the GGE equivalent kind of as a self-check to make sure that the numbers make sense and might fit better with what you have. So after entering those values, you then can look at some of the assumptions.
So here, since we chose electricity, I wanted to go through kind of an explanation of what you might want to do for an electricity calculation.
Lifecycle analysis is really important for when you're doing battery electric type estimations because really where that power comes from will really change your results on your footprint.
So what we have in the tool are a map of basically the 13—these are NERC regions, which are basically used in different modeling exercises but it's covering some of the states that are joined in kind of the grid. So you can go through and choose.
You know, looking at the map, if I'm in Illinois, I would choose Region 4. If I'm in Florida, I would choose Region 8. And you can get a mix based on that area.
Now if you wanted to enter something specific to your very detailed locale and you know that you're getting renewable energy or natural gas energy to recharge the equipment or the vehicles, what you would do is select—you would go in and select 15, so as you see here in red, type in 15.
And then you'd have to go to the spec sheet, so that's the third sheet in the spreadsheet.
And then when you go to the spread—to the specific sheet, you'll see a table. It's table 6, and it has the different grid mixes for each of the different regions, and then the user mix is something that you can go and change and say, well, I want to look at just natural gas completely.
So you would zero out the other values, type 100% for natural gas, or say you wanted it to be a renewable, basically, we lump wind, solar, hydro—all of the renewables except for biomass—into one category. So if you wanted that, you would have 100% there.
And then just go back to the off-road sheets near the results, and then they will pop up there, and you can see I cut off a few of the columns in this to make it a little bit more readable. But for gasoline, here's the value for air compressors, for diesel.
You can see obviously the petroleum use is very minimal for electricity. And then when we get to greenhouse gas emissions, you'll see again those values in that type of format. So it's hopefully fairly—very straightforward, similar to what you might see at FuelEconomy.gov.
So that's kind of hopefully an approach that will be something consistent with maybe the calculations that you have down or looked at in the past.
So some of the final thoughts when you're looking at a fleet's petroleum and carbon footprint—it's both important to understand both the direct impact from operating the vehicle but also some of these indirect impacts that are acquired from producing and transporting the fuel.
And this is really especially important for alternative fuel vehicles. And then while this might sound like a difficult thing to do, there are tools available that can do this in a relatively straightforward manner and do it in a robust fashion. So that's what we try to do.
So that's the end of the presentation. I can turn it over to Sandra for questions. I've also in case people want to get into the spreadsheet or have specific questions, I can go into the spreadsheet and show some of the more details if need be. So...
SANDRA LOI: Great.
ANDY BURNHAM: ...thank you very much.
SANDRA LOI: Thank you so much, Andy. I appreciate it. Operator, can we go ahead and open up the lines for some questions? Cathy? Okay. So while we're waiting for our operator, we did have a question, Andy, that came in over the Web.
Please discuss your assumptions and basis for algal and cellulosic fuels.
ANDY BURNHAM: So what we do at Argonne is we have part of the team I'm on—I'm on the GREET team here at Argonne. We have different researchers working on these different pathways.
So for cellulosic ethanol, some of the default—there are people doing research on wooden biomass, herbaceous biomass, so I guess switch grass versus, say, fast-growing trees.
So in the actual GREET model, we have all kinds of different assumptions that get into the productivity of the land, how many dry tons of material do you get per acre, and what are some of the requirements for, say, fertilizer and things like that? So it gets into real—all of the detail.
What the GREET Fleet tool is—it goes a step above and tries to not get into those details for people who might not be as interested in getting into the nitty-gritty lifecycle analysis.
So if you're interested in trying to get into that level of detail, I'd recommend looking at the GREET tool—GREET model, excuse me, and go into that. It's another spreadsheet. A little bit bigger. It's something like 35 sheets. Each for—there is a sheet for each pathway and so forth. So that's kind of the procedure that I would recommend if you want to get into more details.
And for algae, we also have even more detailed—like a separate spreadsheet that lets you get into real process level designs. So if you're interested in process level design of algae-based fuel, you can get into that. And if you want to have questions, please feel free to contact me. I've provided my email here, and I can get you either to the right place or the right documents, right tools, and we can discuss that.
SANDRA LOI: Perfect. Thanks, Andy. Let's see. We've had a couple—I might have a little bit of technical difficulties. So if anyone does have questions, then put it in the online form, and I'll go ahead and read them off for you.
So from Kay Johnston, her question is, "What is the advantage of using this calculator when we are already using Clean Air Planet? And then also, is there an export that could be used with the GREET tool and the CATP or interface?"
ANDY BURNHAM: Well, I'd like to talk maybe offline about Clean Air.
SANDRA LOI: Sure.
ANDY BURNHAM: And I'm not familiar with that tool. When we developed GREET Fleet, we looked at what was available for the different calculators, and NASA had a tool, and there were a couple of other sources that had tools.
But what the advantage of GREET Fleet is, is that you don't find many tools that have alternative fuel vehicles and especially doesn't let you get into the level of detail of choosing different pathways.
So people who are interested in doing alternative fuel deployment want to get into a little bit more level detail than what is out there that we've seen. So if there are other tools out there, I'd be interested in hearing about them.
But I think really that advantage is the details on alternative fuel vehicles. And then also coming from a data source that is widely used by the Department of Energy really is a key source that is used throughout these types of calculations.
So if California has their things for the low carbon fuel standard, they based their work off GREET. Again, the Department of Energy obviously and the EPA, they use GREET in some of their work. So you're using a data source that is widely used, so that is another advantage.
SANDRA LOI: Great. Thank you so much. So another question that came through: Does the Footprint calculator also calculate for both well to pumps and pumps to wheels on both metrics? They have a comment —I heard that the bigger GREET model does both but wasn't sure if Footprint does as well.
ANDY BURNHAM: The Footprint provides the well-to-wheel results. The details on the well-to-pump side versus pump-to-wheel—they're in the model. They're kind of in the background. So if you were interested in trying to get those results, I could talk to you offline.
It's basically just something that we add together in the spreadsheet without—I think this tool is again to be as hopefully as robust as possible but as simple as possible in presenting the results. So I could—whoever had that question, I can show you how to do it offline.
SANDRA LOI: Great. Thanks, Andy. I have had a question come in about if we would be sharing a copy of the presentation. And, yes, the presentation will be posted as well as the recording on cleancities.energy.gov.
I will be sending out an email post webinar once it is available to everyone on this webinar with a link to that page, but we will be posting it out on our website. So we will make it available to anyone who's interested in it.
Next question: Will EPA accept this in place of the MOOT model, which I could not get to download onto my computer?
ANDY BURNHAM: So the MOOT model is primarily a tool for doing criteria air pollutant emissions. So they probably will not accept it if you're doing air state implementation plans or things like that for, say, carbon monoxide or particulate matter NOx and things like that.
This tool doesn't have that capability. We are working on at least providing this information because that's something that we heard from coordinators and other stakeholders. Well, what about criteria air pollutants?
And kind of as I talked about before, the reason why we moved away from AirCred is because the incremental benefits of alternative fuel vehicles aren't as great as they were in the past.
So the push to, say, a natural gas vehicle, maybe it is a little bit cleaner than diesel, but the push isn't there on the criteria pollutant side just because the standard is so tight.
But we are working to maybe provide some information on that so if people have that question, they can point to this tool or that tool or this data source or something like that to help with those types of questions.
SANDRA LOI: Yeah. Great. Thanks, Andy. Yeah. That question actually came in from Steve Russell, coordinator up in the Boston area. So we certainly can get him that information. So the next one—thank you. Let's see.
So again, folks on the phone, I'm so sorry, we're having some technical difficulties with the phone operator. So if you want to go ahead and type a question, please do so in the online function on the Q&A at the top of your webinar screen.
The next question is: "I noticed that a diesel bus has lower greenhouse gas emission than CNG, LNG, and propane. Is this because of the assumed fugitive emissions associated with natural gas? If so, how were those values determined?
ANDY BURNHAM: Very good question. And for some of the coordinators that have heard some of my other presentations, I talk about some of the research that we've done in this area.
The two areas that are important when comparing diesel to compressed natural gas, or some of the other ones, is really the assumptions on what the vehicle efficiency is. So we're using some default assumptions for a transit bus.
Now getting into the nitty-gritty of transit buses— that compressed natural gas in a spark-ignited engine isn't for efficiency. It's not. That's not the best duty cycle. You're kind of going both low speeds, low loads.
When you compare it to a diesel, using compression in an ignition engine—it's going to have some efficiency benefits there. Really you want to look at what information you have. Maybe you have better data where you're saying it's not going to be similar to the default.
It might be a little bit different. So that's what I would recommend. But basically, if it's going to be that, question is it shows that it's close. You're not going to have huge benefits for a compressed natural gas, say, transit bus versus a diesel bus.
Is it a little bit lower? Is it a little bit higher? It really depends on a lot of those factors. And yes, the second part is on the methane leakage. Yes, that is an important part. As part of the GREET effort, we did some research in that area, and that's been kind of a thing that has been in the news a lot.
Is that the methane leakage from natural gas is an area that people are questioning. EPA has increased their emission estimates. We have worked on this and developed some papers and things like that, but it's still fluid.
And so I think the question is that maybe the methane leakage may not be as good. There's regulations and things like that that might help reduce those emissions.
So I think we're always trying to keep on top of these issues, and that's why we update the model because in certain cases, it can be somewhat fluid depending. Will things change completely? No.
I mean we're—you're talking kind of at the margins. You might change some parameters—say, 10% or something like that. But we do try to keep on top of these issues.
SANDRA LOI: Great. Thank you so much. Next question: Can we get the formula for each energy source? Example, what's the net GHG for one gallon of diesel, unleaded E85, etc.?
ANDY BURNHAM: You can view that through the calculation in GREET. I mean in the tool. So when I did the second demo, basically, the two options you have: Do you choose how many vehicles, the mileage and the fuel economy, or do you just choose how much fuel you use?
But what you can do is, say, type in, say, one gallon of gasoline or one gallon of diesel. And the problem is since that's such a small number and we're doing it in short in barrels, you're not going to see a value. It's going to be there.
You could copy and paste the value and actually get something, or you could do 10,000 or 100,000, or a million, say, a million gallons and you could get the calculation and do the conversions, and you can get there.
And if anyone, if that person has a specific question for me, just feel free to contact me, and I can walk you through that.
SANDRA LOI: Great. Thanks, Andy. Again, if anyone has a question, please type it into the online form at the top where you see Q&A. You can go ahead and type in your question directly that way. We are having some technical difficulties with the phone lines.
Next question for you Andy: To what extent have you updated GREET assumptions with the 2011 EPA medium- and heavy-duty truck GHG final rulemaking?
ANDY BURNHAM: We haven't updated GREET to incorporate that. I think that is an important step for us to get better data for medium/heavy -duty vehicles. We are working with—I mentioned previously the autonomy team, so that's a vehicle simulation tool that we have here.
And so there has been more effort to examine medium- and heavy-duty fuel economy. So I have worked on that actually in a separate tool that we're looking at. So it is an area that we are keeping on top of. It doesn't—those values aren't included in GREET Fleet.
What we wanted to do for GREET Fleet is provide defaults that are reasonable, but we highly stress that you should try to use your own data.
And so in cases where you don't, it's not easy to find the data to try and reach out to some of the vehicle manufacturers, the dealers that might have that information or might be able to give you a better assumption to say, well, our vehicle technology is about the same as a diesel or something like that.
And you can go that way. So that is one of the most tricky areas in this when trying to do these calculations. So we are again—that's another area as a research institution where we're continually trying to do to make sure that we have the latest and best data.
So I think it's still to be determined. There are those rules from EPA to help reduce, I guess, the greenhouse gas emissions from medium/heavy-duty vehicles.
And those technologies are some of them—are on the road—some of the regulations will be coming through, and we'll see if we can have better simulations that can do that for alternative fuel vehicles that are proposed.
SANDRA LOI: Great. Thanks, Andy. Another question: Sorts of fuel—why is it important to know where fuel comes from?
ANDY BURNHAM: So I mean in a simplistic way, we're trying to be energy accountants basically. And when you have a fuel that comes from a different source, it might undergo many different processes or different steps to get it to that fuel that you want.
So I guess an example is, say, for ethanol, and people have their concerns about corn ethanol. And say, well, you can go to, say, a cellulosic ethanol, and there's much more benefits to it.
So what we try and do is look at, well again, how much energy is required to go into farming corn, and how much energy is required to produce, say, switch grass or some poplar tree or something like that?
And so the answer is really, there can be a significant difference in the greenhouse gas impacts of using different fuels that come from different feed stocks. So the impact of corn ethanol is different than it is for switch grass–based ethanol versus the sugar cane ethanol from Brazil.
So it really can change the answer, so I think to give you some rough numbers—so there might be like a 20% reduction in GHGs for corn ethanol compared to gasoline. If you get to a cellulosic ethanol, it might be 70%, 80%, or something like that.
So you have a much larger benefit from a different—the same fuel but a different place where it came from. So that's the reason why. And the same thing for electricity— you want to know is it coming from coal?
If it's coming from coal, you're going to have significant greenhouse gas emissions.
If you're in the Northeast and you're using a petroleum—there's not many out there, but if you're using electricity from a petroleum residual oil power plant, you're using both oil, and it's actually creating a lot of greenhouse gas emissions compared to, say, natural gas or wind or solar or something like that.
So that's the reason why we look into the different sources of where they come from.
SANDRA LOI: Great. Thank you so much. Another question is: We report four numbers including NOx, HG and SO. Where do those numbers get reported?
ANDY BURNHAM: Sandra, NOX—what was the second one?
SANDRA LOI: Oh no. So they're abbreviations, so it's NO, HG, and SO.
ANDY BURNHAM: HG? Well HG, I'm guessing, is, maybe could be mercury or hydrocarbon gases? That person might want to get back to me. But...
SANDRA LOI: Okay.
ANDY BURNHAM: ...those are in all likelihood NOX and SOX. SO is sulfur oxide. Those are criteria pollutants. So as I mentioned before, this tool doesn't include that data. It is only for greenhouse gas emissions and petroleum use. We are working on potentially including criteria air pollutants in maybe a future tool.
So this tool would not provide that information. If that person wants to again touch base with me, I can potentially help them with that question offline.
SANDRA LOI: Great. Thanks. Yeah, it was mercury, and it's probably the criteria pollutants like you were mentioning. So I'm not seeing any new questions, and someone has sent over some suggestions, and I will share those with you Andy. So thank you so much.
If you do have suggestions for the tool or additional feedback, feel free to reach out to Andy directly. Andy, do you have any closing remarks before we go ahead and end the webinar today?
ANDY BURNHAM: No, I just wanted to thank you for the opportunity to speak. And I hope that this tool will be useful for people. And if they have any questions, please feel free to shoot me an email and touch base with me.
SANDRA LOI: Great, thank you so much for your time today, Andy. As I mentioned, this is Sandra Loi again from NREL. We will be posting it on the Clean Cities website.
I will send an email to all of the participants from today's webinar with a link to the slides and the recording once it is posted. It should be within the week.
And as you can see up on the screen right now, there's a link to our Clean Cities website where you can contact your local Clean Cities coordinator as well as find archives of past webinars, our Alternative Fuel Data Center, where you can actually find a link to the GREET Fleet Footprint Calculator as well as several other tools and additional resources that may interest you.
And if you are interested in being included on all future Clean Cities webinars, feel free to reach out to me and send me an email at my email listed: firstname.lastname@example.org. Thank you so much for participating, and we'll speak to you soon. Have a great week.