Availability of CARB’s EMFAC2021 Technical Document and a Model Update (v1.0.1)

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April 30, 2021

Availability of CARB’s EMFAC2021 Technical Document and a Model Update (v1.0.1)

The California Air Resources Board (CARB) is officially releasing EMFAC2021 Technical Document, which summarizes the input data and methodologies embedded in EMFAC2021. 

EMFAC2021 is the latest emission inventory model that CARB uses to assess emissions from on-road motor vehicles including cars, trucks, and buses in California, and to support CARB’s planning and policy development. This newest model reflects CARB’s current understanding of statewide and regional vehicle activities, emissions, and recently adopted regulations such as Advanced Clean Trucks (ACT) and Heavy Duty Omnibus regulations. It represents the next step forward in the ongoing improvement for EMFAC.

Users may find the EMFAC2021 Installation Package, Technical Document, Handbook for Project-Level Analysis, and User's Guide on CARB’s website for Mobile Source Emission Inventory (MSEI).

EMFAC2021 Technical Document

At the same time, CARB is releasing an updated version of the EMFAC2021 software. This version (v1.0.1) will replace the current version (v1.0.0) that was previously released on January 15, 2021. The new version will be submitted to the U.S. EPA for approval.

Download EMFAC2021 (v1.0.1)

This new version addresses some of the issues related to Project-Level (PL) mode of the model when users intended to integrate emission rates by truck/non-truck, or truck1/truck2/non-truck. The updated version also reflects bug fixes related to start emissions of Plug-in Hybrid Electric Vehicles (PHEV), and CO2 emissions from heavy-duty vehicles of model year 2023 and later. In addition, minor updates have been made for modelling emissions of motorcycle and light heavy-duty vehicles, as well as energy consumption of medium heavy-duty vehicles. The impacts of these updates are shown in details on CARB's MSEI website

The corresponding EMFAC2021 (v1.0.1) web database is now available at: 

EMFAC Web Platform

The EMFAC2021 web platform allows users to download emissions data with default activity, produce emissions using custom activity inputs, the same as EMFAC’s Custom Activity (SG) model, and generate emission factors using user-defined ambient temperature and relative humidity for project level assessment (PL). In addition to the latest EMFAC2021 (v1.0.1) model, the EMFAC2017 (v1.0.3) web platform features still remain accessible to users. Before the approval of EMFAC2021, EMFAC2017 is still the currently U.S. EPA approved version of EMFAC. A training video with guidance on how to use the web platform is also available on the website.

For more information or questions on EMFAC, please contact us at emfac@arb.ca.gov.