Revised Models for Determining Direct Lifecycle Emissions of Fuels

California Air Resources Board (ARB)

[Green Car Congress] California Air Resources Board (ARB) staff have posted version 2.0 of the California-Modified Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation (CA-GREET) Tier 1 and Tier 2 models. In 2009, ARB approved the original LCFS regulation order. That order designated CA-GREET, version 1.8b, as the model to be used for estimating direct life cycle emissions from the production, transport, and use of transportation fuels. CA-GREET 1.8b has remained in use since this original Board approval.

The regulation order the Board will consider at its July 2015 hearing replaces CA-GREET 1.8b with CA-GREET 2.0. Both CA-GREET versions are based on versions of the national GREET model developed at Argonne National Laboratory. The version currently in use was developed from Argonne’s GREET 1.8b, and the proposed new version was developed from GREET1 2013.

In the proposed regulation, first- and next-generation fuels are referred to as “Tier 1,” and “Tier 2” fuels, respectively.

Tier 1 refers to conventionally produced first-generation fuels (e.g., starch- and sugar-based ethanol, biodiesel, renewable diesel, compressed natural gas, liquefied natural gas). Tier 2 refers to next-generation fuels (e.g., cellulosic alcohols, hydrogen, drop-in fuels).

ARB staff has also posted the Oil Production Greenhouse Gas Emissions Estimator (OPGEE) version 1.1 Draft E. The revised model and associated documentation are used to estimate carbon intensity values for crude oil.

These updated models are incorporated by reference into a 15-day change rulemaking package. Assuming the Board adopts this package, these models will be used to calculate the Carbon Intensity of the fuels under the Low Carbon Fuel Standard Program.

The Low Carbon Fuel Standard requires a 10% reduction in the carbon intensity of fuels sold in California by 2020.


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