Changing fuel type for feedstock transport in GHGenius 5.02

7 months 2 weeks ago #472 by erin.yip
Hi, I have a question regarding feedstock transport of organic waste to plant using trucks. Is it possible to change the truck fuel to RNG?

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7 months 1 week ago #473 by doconnor
The alt fuel for trucking (row 92 on Transport) is currently set to use canola biodiesel.

You will see that on the exhaust emissions sheet in row 176, column M that there is a space for RNG but it is blank. A user should be able to see what was done in N176 and how it is used on the upstream results sheet to add that capacity to a model.

Don O'Connor

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7 months 1 week ago #474 by erin.yip
Hi Don, thanks for your response! To ensure that we are using the tool properly, could you please describe the steps we must take to use an RNG truck for the feedstock transportation calculations?

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7 months 1 week ago - 7 months 1 week ago #475 by rdo
This is a bit of the model that has been half implemented for a very long time. I've been taking a look at it and it's closer to usable than I thought. Any cells I reference are going to be specific to GHGenius 5.02b.

To start off we'll need to set the truck distance on the Input sheet in cell BA80. Set the truck fraction to 1 or whatever non-zero input is appropriate for your pathway.

On the Transport sheet navigate to BA47 and BA48. Row 47 takes off the input sheet for the fraction transported by diesel truck. Row 48 is hardcoded at 0 and represents the fraction transported by alternative fuel truck. Typically those two cells would be 1 for diesel and 0 for alt fuel. Depending on how you want to use this model we're about to alter, there are a few ways to approach the changes.

I would suggest setting BA47 to 0 and BA48 to =Input!BA86

By making the change this way, the truck fraction input on the Input sheet will still work but it will apply entirely to trucks using an alternative fuel. If you had a scenario where it was only 50% alternative fuel trucks then maybe you would set both BA47 and BA48 to =Input!BA86 * 0.5

At this point the changes made are functional and will impact the output sheets including Upstream Results HHV and BC LCFS. However, I can look at the formula on Upstream Results HHV in both cells CR12 and BQ12 and tell you that the alternative fuel being used is biodiesel from canola oil. This is because of the use of cell 'Exhaust Emissions'!N176. Row 176 has a few options for alternative fuels, but no RNG so let's add it.

There's already a space for RNG in row M, it just wasn't implemented. The easiest way to do this is to assume the truck is the same as the existing LNG truck, but with RNG. So we'll start by copying the formula from E176 into M176 then modify it.

The first term of ='Vehicle Assembly'!H51 can remain the same as it references a highway truck. The second term of 'Upstream Results HHV'!P21 needs to point to the appropriate RNG pathway on Upstream Results HHV. I'll assume this is RNG made from the organic waste so it can be changed to 'Upstream Results HHV'!BQ21. Because it's a renewable pathway, the third term of O149 should be changed to O150. The final term can also be left alone as it refers to burning any liquified natural gas. Putting it all together:

Cell M176: ='Vehicle Assembly'!H51+'Upstream Results HHV'!BQ21+O150/'Vehicular Energy'!E130

The final step is to go back to Upstream Results HHV and adjust row 12 in your pathway to point to 'Exhaust Emissions'!M176 instead of 'Exhaust Emissions'!N176.
Last edit: 7 months 1 week ago by rdo.
The following user(s) said Thank You: erin.yip

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7 months 1 week ago - 7 months 6 days ago #478 by erin.yip
Hi, thanks so much for the detailed response! For some additional context, the pathway that we are modelling is the production of RNG using organic waste. If the feedstock transportation truck also uses RNG produced from organic waste, would this create any double counting issues or circular references in the tool?

To illustrate my question: the emissions from the RNG truck is dependent on the emissions from RNG production using organic waste, but the emissions from RNG production also depends on the emissions from the RNG truck.

I bring this up because I noticed that "feedstock transport" becomes negative in the BC LCFS tab, as if there were avoided emissions associated with the use of RNG in the transportation of the feedstock.

If this does result in double counting, is there a way for me to calculate the emissions associated with feedstock transportation only?

Please let me know if anything is unclear - thank you!
Last edit: 7 months 6 days ago by erin.yip.

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7 months 6 days ago #479 by rdo
What you're describing is actually expected behaviour. If your pathway is negative enough then burning the fuel still leaves you with less greenhouse gases in the atmosphere than when you started. Usually we'd only see this with sequestering biofuels, but avoiding methane emissions can do it too. While the behaviour is circular, it's okay and expected as long as the fuel going into your transportation trucks is the fuel you're producing on site.

There is an edge case where it's not okay though. The circular reference becomes an issue if the fuel you're modelling is not exactly the fuel you're fuelling the trucks with. For example if the RNG trucks are actually refilling at a regional depot then the transportation emissions should be using industry average emission values instead of your modelling pathway.

There would be two possible ways to solve that:
1. On Exhaust Emissions M176, reference a different pathway on the Upstream Results sheet.
2. On Exhaust Emissions M176, hard code the model default Upstream Results value.
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