Transportation distances for each chemical are determined using the 2007 U.S. commodity flow survey.
Hydrogen gas is required in the acetogen pathway to hydrogenate acetic acid to ethanol.
It is modeled to be produced from a standalone steam methane reforming (SMR) plant (Table 5).
Natural gas is used as the methane source and is also combusted to provide the necessary process steam and heat for hydrogen production.
Excess high pressure steam is converted to electricity at 30% efficiency.
It is assumed that this electricity would be cycled back into plant operations, thereby decreasing the amount of electricity imported from the U.S. national grid.
Operations and emissions data from this process are provided by an Idaho National Laboratory report.
Production of hydrogen gas is kept separate from other chemicals to identify its contribution to the life cycle impact assessment.