Many biofuel standards, including California's recently adopted low carbon fuel standard, consider just one feedstock from one supplying country for the production of sugarcane ethanol: fresh mill-pressed cane juice from a Brazilian factory. While cane juice is the dominant feedstock for ethanol in most Brazilian factories, a large number of producers in Indonesia, India, and the Caribbean, and a significant number in Brazil, manufacture most of their ethanol from molasses, a low value co-product of raw sugar. Several producers in these countries have the capacity to export ethanol to California, but the GREET (from: greenhouse gas, regulated emissions and energy use in transportation) model, which is the LCA (lifecycle assessment) model of choice for most biofuel regulators including California, does not currently include this production pathway. We develop a modification to GREET to account for this pathway. We use the upstream and process lifecycle results from the existing GREET model for Brazilian ethanol to derive lifecycle greenhouse gas emissions for ethanol manufactured from any combination of molasses and fresh cane juice. We find that ethanol manufactured with only molasses as a feedstock with all other processes and inputs identical to those of the average Brazilian mill has a lifecycle GHG (greenhouse gas) rating of 15.1 gCO₂- eq MJ⁻¹, which is significantly lower than the current California-GREET assigned rating of 26.6 gCO₂- eq MJ⁻¹. Our model can be applied at any level of granulation from the individual factory to an industry-wide average. We examine some ways in which current sugarcane producers could inaccurately claim this molasses credit. We discuss methods for addressing this in regulation.