California Air Resources Board

The Alternative Diesel Fuels (ADF) regulation is intended to create a framework for low carbon, and often times lower polluting, diesel fuel substitutes to enter the commercial market in California, while mitigating any potential environmental or public health impacts.  ADFs are those alternative diesel fuels that do not have an established CARB fuel specification in place prior to January 1, 2016.  Through California and federal fuel policies, consumers are beginning to see increasingly cleaner and more diverse fueling options.

The ADF regulation consists of two major parts:

1. A three stage process for ADFs to be introduced into the California market including, if necessary, a determination of mitigation measures to ensure no degradation in air quality.
2. In-use requirements for biodiesel as the first ADF.

The ADF regulation consolidates many administrative and regulatory practices into one regulation that provides a clear framework for commercialization of ADFs. The formal framework is necessary for two primary reasons. First, programs such as California's Low Carbon Fuel Standard (LCFS), and the federal Renewable Fuel Standard (RFS) are incentivizing the rapid development of ADFs. Many of these fuels provide criteria pollutant and toxic air contaminant emission reductions in addition to their greenhouse gas (GHG) benefits. Second, some ADFs may have adverse effects under certain circumstances. For these reasons, CARB adopted the ADF regulation to ensure that ADFs are commercialized in California under specific requirements and conditions that avoid potential adverse impacts, while realizing the benefits that ADFs can provide.

The first ADF that is subject to in-use requirements under the ADF regulation is biodiesel. Fuel specifications and other requirements for future ADFs will be incorporated in the the ADF regulation through the formal rulemaking process. Biodiesel has particulate matter (PM), GHG, and other emissions benefits; however, testing by CARB and others shows that biodiesel can increase oxides of nitrogen (NO_x) under certain circumstances and without considering offsetting factors. The biodiesel in-use specifications will reduce NO_x from current levels and Californians will continue to experience biodiesel's PM, GHG, and other emissions benefits.