# Megan emission factor is different between v3.2 and v2.1

**URL:** <https://forum.cmascenter.org/t/megan-emission-factor-is-different-between-v3-2-and-v2-1/4724>\
**Category:** MEGAN\
**Created:** [February 20, 2024, 6:45am UTC](https://forum.cmascenter.org/t/megan-emission-factor-is-different-between-v3-2-and-v2-1/4724 "2024-02-20T06:45:27Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![liuhao](https://avatars.discourse-cdn.com/v4/letter/l/ea5d25/32.png) [@liuhao](https://forum.cmascenter.org/u/liuhao)\
**Post date:** [February 20, 2024, 6:45am UTC](https://forum.cmascenter.org/t/megan-emission-factor-is-different-between-v3-2-and-v2-1/4724/1 "2024-02-20T06:45:27Z")

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Hi everyone,

When running the megan model, I noticed v2.1’s EF is classified according to CLM-PFT, the EFv210806.csv file of v3.2 also contains CLM-PFT: 1-15. However, I observed significant differences in the magnitude of EF values between v3.2 and v2.1. Initially, I thought this difference was due to unit conversion (The units for v3.2 are unknown while v2.1 use ug m-2 h-1), but the relationship between the two is not proportional. What could be the reason for this discrepancy?

If I want to add a new tree species (Pinus massoniana) to the EFv210806.csv in megan3.2, and the EF units provided in the literature are μg C g−1 hr−1, what conversion method should I use to add the EF to EFv210806.csv?

Thank you very much for your help  
Figures 1 shows the emission factors for v2.1, while Figures 2 and 3 represent the emission factors for v3.2, which are identical.

 ![2.1](https://canada1.discourse-cdn.com/flex027/uploads/cmas/original/2X/6/6725c7aab4fdf5d6b516d71ace8a4a51446f74f6.jpeg)  
 ![微信截图_20240220145100](https://canada1.discourse-cdn.com/flex027/uploads/cmas/original/2X/3/3bc647bb7df2ca97571482235a8ef68ee6feff17.jpeg)  
 ![3.2](https://canada1.discourse-cdn.com/flex027/uploads/cmas/original/2X/a/afc3c3f42ab9005417a377917752522bce981c4d.jpeg)

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**Author:** ![willison.jeff](https://avatars.discourse-cdn.com/v4/letter/w/c89c15/32.png) [@willison.jeff](https://forum.cmascenter.org/u/willison.jeff)\
**Post date:** [February 20, 2024, 2:08pm UTC](https://forum.cmascenter.org/t/megan-emission-factor-is-different-between-v3-2-and-v2-1/4724/2 "2024-02-20T14:08:12Z")

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Hi @liuhao,

Thank you for sharing this finding. Unfortunately, this question is upstream of the MEGAN code used in CMAQ. The MEGAN 3.2 preprocessor is developed by Alex Guenther (alex.guenther@uci.edu) and his team. He is not active on this forum so I recommend emailing him directly.

-Jeff