Hello. I am Sally, a new member of MATSURI. I am good at biology, but I am still a novice when it comes to environmental impact assessment and related activities.
～Summary of the previous episode～
Learning starts with "imitating," so I decided to try out a software called GREET that I saw in an internal report about environmental impact. Even just installing it was a struggle, but I managed to complete the installation and get the software running!
~End of synopsis~
GREET activated!
When you launch this software called GREET, it already contains the numerical values and flows of various products and raw materials. For example, let's look at corn ethanol SAF (Sustainable Aviation Fuel), which uses ethanol made from corn to make jet fuel. Select Sustainable Aviation Fuel (SAF) from the software's Products menu, then select Ethanol- To Jet: Satandalone from Corn.
I see. I got some cool diagrams. But I don't really understand them. ( ﾉД`) Sob sob... When I don't understand something, I just read the manual [1]. It's over 100 pages long, but I'm reading it with enthusiasm💪.
GREET is software created and managed by the Argonne Laboratory, a research institute of the U.S. Department of Energy [2]. Since it is under the jurisdiction of the Department of Energy, it can calculate the amount of greenhouse gases (GHG: including not only carbon dioxide but also methane and alternative fluorocarbons) emitted from the production and consumption (combustion) of fuel and energy, substances that cause acid rain, and the amount of water used. There are various software programs around the world for calculating environmental impacts, but GREET is widely used for fuel, and conversely, it seems that GREET is not used much for anything other than fuel. In the MATSURI project, we make not only fuel but also various other things, including daily necessities and food. In other words, Sally has to learn how to use and work with other software and databases? This is difficult...😅.
Let's consider the life cycle of fuel. First, it can be divided into two parts: the stage at which it is produced so that it can be used as fuel, and the stage at which it is used as fuel for what kind of vehicle. In technical terms, this is called WTP (Well-to-Pump) and WTW (Well-to-Wheel). WTW plus the emissions related to the manufacture of the vehicle is called C2G (Cradle-to-Grave). These correspond to the "WTP Results" tab and the "WTW and C2G Results" tab in GREET. The cool diagram that appears in the bottom right of the "WTP Results" tab shows the flow of how fuel is made [3]. The amount of raw materials and the amount of electricity used in each process are entered as numerical values. The amount of GHG emitted when making raw materials and energy is entered in the software as a data set (for many raw materials and energy, but not for some), and calculations can be made using these numerical values. And in the "Emissions" at the bottom left, the amount of carbon dioxide emissions and the amount of SOx that causes acid rain are displayed. I see, I understand a little now!
A window that appears when you click on a flow. It shows the amounts of raw materials and energy used.
Now, in September 2023, there was a topic about GREET. The American Ethanol Association asked the US government to use the latest GREET model values for corn ethanol SAF [4].
At first, when Sally heard this, she was confused and asked, "??? Aren't we already using GREET's numbers? What do you mean, we're using GREET now and you want us to use GREET again?"
Let's clarify what is confusing us. The request of the US ethanol group is "Should we use the GREET model of the US Department of Energy instead of the CORSIA model, which is often referenced in the global aviation industry, to calculate the GHG emissions value of corn-based ethanol SAF?"
CORSIA[5] is the abbreviation for "Carbon Offsetting and Reduction Scheme for International Aviation". Although the CORSIA model is not the official name, there is a calculation method for GHG emissions that CORSIA adopts. Based on this calculation method, it has published standard values[6] for GHG emissions of biofuels produced in various countries and regions. It is assumed that the latest GREET model refers to the "GREET.net 2022" version.
Here, I will briefly explain the background of the "XX model" part. In this article, the model is
1. If it's called SAF, you have to be able to say that you can reduce GHG emissions by X% compared to the past (from fossil fuels). 2. To do that, you have to calculate the GHG emissions. 3. The extent to which you include it in the calculation can vary depending on the time, place, idea, and system. 4. Calculating from here to here in this way is called "using the XX model."
In other words, the ethanol organizations are proposing a change in the way the calculations are done, saying, "This is how we calculate it now, but wouldn't this calculation be better?"
So I looked into the CORSIA standard values and the latest GREET model for corn-based ethanol SAF. This should be helpful for calculating GHG emissions when making SAF from algae!
We will explain the detailed differences between the models on the MATSURI members-only page at a later date! Stay tuned!
Here, I would like to consider the background of the ethanol group's request. Since they are making a request to the US government, it is assumed that the aim of the US ethanol group is to make corn ethanol produced in the US, etc., an SAF eligible for subsidies under the IRA (Inflation Reduction Act, enacted in August 2022) as the total emissions calculated from GREET.net 2022 are more than 50% lower than existing jet fuel (89 g CO2e/MJ). The amount of IRA subsidies and tax credits is very large, so it is likely that they are actively working with this in mind. Another possible aim is to aim for a CORSIA-certified SAF (CEF) with GHG emissions more than 10% lower than existing jet fuel. However, in this case, the request is made to the ICAO International Civil Aviation Organization, which operates CORSIA, rather than the US government. What is surprising here is that even for aviation fuels that are not derived from fossil resources, there are systems that are eligible and systems that are not eligible because the standards and certifications for SAF vary depending on the country's laws and international systems. I was surprised to learn that there is no unified view on SAF, and that it is included in multiple systems.
What I realized while researching and studying is that the method of calculating greenhouse gas emissions is not completely fixed, but is changing. It is a big headache for the person doing the calculations. However, the idea that "if we don't take these things into account, we can't call it sustainable" is very helpful for MATSURI. Also, since there are multiple calculation methods and they can change, it doesn't seem very honest to just publish a number like "GHG emissions are XXg" because it is unclear how much was taken into account (whether it was included in the calculation). To be honest, MATSURI is a project that disseminates honest information, so I thought it would be necessary to also disseminate information such as "Under this scenario, it will be like this" and "When calculating, we use XX model, and we include up to XX in the calculation and do not include XX in the calculation."
I was also surprised at how many things need to be considered, examined, and various software used just to estimate greenhouse gas emissions from fuel use, and I feel dizzy at the difficulty of the road ahead. In the sustainable algae-based society that MATSURI aims for, of course, we envision uses other than fuel, such as everyday items like plastic products and as food. In other words, we need to make calculations for each use. Furthermore, when considering sustainability, we need to organize not only greenhouse gas emissions, but also issues such as water usage and competition with food. There's a lot to do!
This time, I started up the GREET software and looked at it while studying the manual, related news, and calculation methods. I think I'll do some actual calculations using the software next time.
Stay tuned for next time!
[1] Official User Guide from Argonne Laboratory https://greet.anl.gov/files/greet-manual
[2] Official description of GREET by the Office of Energy Efficiency & Renewable Energy
https://www.energy.gov/eere/greet
[3] Official quick guide to the "WTP Results" tab: https://greet.anl.gov/greet/gettingstarted/wtp.html
[4]”Ethanol Industry Associations Ask Treasury Secretary To Use GREET Model For Scientific Accuracy”September 14, 2023 https://ethanolrfa.org/media-and-news/category/news-releases/article/2023/09/ethanol-industry-associations-ask-treasury-secretary-to-use-greet-model-for-scientific-accuracy
[5]What is CORSIA? https://www.icao.int/environmental-protection/CORSIA/Pages/default.aspx
[6]ICAO document - CORSIA Default Life Cycle Emissions Values For CORSIA Eligible Fuels https://www.icao.int/environmental-protection/CORSIA/Documents/CORSIA_Eligible_Fuels/ICAO%20document%2006%20-%20Default%20Life%20Cycle %20Emissions%20-%20June%202022.pdf
written by : Sally
◾️List of articles in this series
#1: I think I'll start by trying something called GREET.
# 2 : How do you calculate greenhouse gas emissions when used as fuel?
# 3 : What is the purpose of LCA of algae?
