Transport input (t*km) - why do I get an absurd high result?

Question

Hi members

I am modelling a process that includes a transport flow (t*km). The tonnes freighted is 300,000t and my distance travelled is 63700km (by vessel). The output is 187,942 tonnes of CO2eq. It is per year, but seriously, it shits up my product system completely. What am I missing here? What adjustment do I need to do? Is it the input value that is wrong, or my provider (using default linkage)? The transport process that I use comprises the impact per t*km for a vessel said to transport an average of 3,800 mtonnes.kms over a life time of 25 years. I sense some kind of adjustment is needed here, but not where.

Thanks!

Answer 1

Hello Miae,

I imagine the transport distance is wrong. The calculation is usually done as follows:

1. Calculate the total amount needed to transport, and vehicle type (check)

2. Calculate the average length of a trip (not sum of the length of trips)

3. Input given value into process, and check results.

I imagine that the average length of a trip is not 63.700 km. In the calculation you have done, you say that each ton is transported 63.700 km, which would give you an insane number.

I would recommend redoing the calculation, which hopefully will give you a more reasonable result.

Best of luck.

Comments

Hi Matias. Thanks a lot for your question. I will try and run the model with adjusted distance.

A bonus question: I need to include empty return trips, how would you model that considering above mentioned steps? I was thinking of adding it as 1*distance, but that conflicts step 2. (ps. I can only choose processes for ship transport in t'km).

Thanks for your reply!

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Hello Miae,
Most processes such as transport by truck, includes empty return trips in the process.
If the chosen transport process does not include empty return trips then consider if its realistic that the ship will return with no cargo. In the example of a container ship, it will almost never return with no cargo.

If you are convinced of the empty return trip, then i would take an existing process, investigate the fuel use per tkm in the unit process, calculate the fuel used for an empty return trip using secondary literature, and calculate the amount of "tkm" you would need to use that amunt of fuel. Remember to allocate only a part of that fuel use to your return trip.

This is a slightly complicated exercise, but im sure you can do it. Good luck.

Answer 2

Hi there,
don't know if I completely understand your case but it seems like you added up all transportation routes that have to be done to move the 300,000 t. I think you just have to use the total mass moved (300,000 t) and the single distance from place A to place B (some 1000 km maybe) to model the transportation emissions.

This would explain why the emissions are too high, even though I'm not 100% sure if I understood the modeling approach correctly. Maybe cross-check in one of the official openLCA tuts on YouTube.

Best regards

Comments

Hi schubele

Thanks for your answer. You did understand the case correctly, and I will try and model it in adjusted distance. Much appreciated.

Answer 3

Hi, I made this math...

With your load and distance get the (t*km) unit. It should be approx 1,91E+10

Then divide it by your emissions to get (CO2/t*km) unit and it should be approx 9,83E-06

Now, you have your Results for every ton and km. Obvioulsy it is a linear regression without limits. In example, whrn the ship goes empty, you get 0 CO2. But I believe that if you use it with logic the result will be fine.

I'm not expert in LCA. I'm just lerning... so every feedback is welcome!