Hello,
For a project in the manufacturing industry we are looking into the GHG emission for HDPE & PP. The company is producing PP & HDPE products and has primary material but also closed and open loop material. We found the outdated emission factor in UKgov from 2023, which are not updated in 2024. But we noticed that open loop source with an emission factor 600 kgCO₂e/tonnes is substanially lower than the closed loop factor with 2346.68907 kgCO₂e/tonnes. It seemed to us that open loop would have higer emissions than closed loop due to the origin of the material being known. We suspect that the emission is so high due to limited volume of the product being available and thus having higher energy usage then open loop where primary material can still be used to replenish. Does somebody have an sound conclusion to why? Thanks in advance.
Hi Stijn,
Thank you for sending this.
Reading your description, I believe the only correct conclusion is that the “open loop” emission factor is not suitable for a situation where the origin of the product is unknown. Closed-loop seems appropriate for products “where the exact origin is known.” But for the others, you’ll need to find a more suitable emission factor. (My advice on this is in the next point.)
- Why open-loop is not suitable
Let’s stay with HDPE plastics for this explanation:
- Closed loop refers to a recycling process where HDPE is recycled into HDPE.
- Open loop refers to a process where HDPE is recycled into any other end product, likely a lower-grade plastic.
But this concerns the producer of this (recycled) plastic, not the recipient (user of recycled plastics).
The correct way to use this is for someone converting HDPE into garden chairs. So, not your situation.
I personally find this emission factor a bit tricky because the factor itself is not wrong, but due to its naming, it’s very easy to misinterpret (as in your case).
For this exact reason, it has not been republished by UK.Gov since 2022. You will also see on our platform that this is still sourced from 2021.
We have a “grace period” of 18 months for old emission factors. If you use this after July 2023, it will no longer be available.
But I suspect you were logging this before the beginning of 2023?
All references with screenshots are at the bottom of this email, along with the links:
Source screenshots:
Documentation from UK.Gov 2022 (mentioning the open-loop issue)
https://assets.publishing.service.gov.uk/media/62aee1fbe90e0765d523ca33/2022-ghg-cf-methodology-paper.pdf
WRAP (source of open-loop and closed-loop EFs)
https://www.wrap.ngo/sites/default/files/2021-06/Carbon%20WARM%20Report.pdf
- What to do
I believe I understand the situation: you’ve already communicated about these emissions and are now being asked to substantiate them better?
In that case, implementing a correction is indeed a bit tricky. But it is still the right thing to do.
You could argue that after communicating with the publishers of the EF, it has become clear that the factor is not entirely suitable for this situation.
It is indeed a complex matter!
Options for a more suitable EF for these plastics are:
- Primary plastics production
• It could be argued that “unknown source” equals new material.
- The same closed-loop
• It could be argued that the difference between known and unknown source is not significant enough at this fairly coarse resolution.
- Another emission factor for “Recycled polyethylene” from Ecoinvent (see screenshot)
• For better nuances regarding locations and recycling grades, Ecoinvent is much more suitable (though obviously more complex).
• For example, you could choose “Rest of the World” because the location is unknown.
• Not sure if you’re familiar with Ecoinvent, but “market for…” simply adds transport and trading to a product and is usually what you want (the difference from the direct product is negligible with plastics).
• The advantage is that with some clever choices, you might find one that “doesn’t differ too much” from your previously reported 600 kg/ton?
• For consistency reasons, it would be better to switch the other EF of purchased plastics to Ecoinvent as well.
I hope this has helped?
Regards,
Steven
