AC Transit (Alameda-Contra Costa Transit District), which operates the third-largest public bus system in California, has filed a fuel pathway application for gaseous hydrogen produced via electrolysis powered by renewable electricity (solar) with the California Air Resources Board (ARB) under the Low Carbon Fuel Standard (LCFS) regulation.
According to AC Transit’s analysis—which is supported by ARB Staff—the carbon intensity (CI) of the gaseous hydrogen produced by the pathway is 0.00 gCO2e/MJ—i.e., a zero-carbon fuel on a “well-to-tank” lifecycle basis.
AC Transit, which has been building a hydrogen fuel cell demonstration program since 2000, operates its own hydrogen fueling facility in Emeryville, CA. The total hydrogen dispensed includes on-site production as well as hydrogen supplied by the Linde Group. The on-site hydrogen is produced using a proton electrolyzer and two compression units.
The electrolyzer unit has a capacity of 64 kg H2/ day and the facility currently produces approximately 750 kg of compressed H2 per month. The hydrogen produced by electrolysis is mixed with hydrogen delivered by Linde and compressed at the two compression units. The compressed hydrogen is finally delivered to heavy-duty (HD) and light-duty (LD) fueling stations at the same site.
Electricity for the on-site generated hydrogen is sourced from two solar installations with rated outputs of 425 kW and 510 kW. All of the generated solar electricity offsets all electrical energy required for electrolysis and hydrogen compression at the facility. Because AC Transit is not claiming credits for its solar electricity, calculates a CI of 0.00 gCO2e/MJ for this pathway based on lifecycle analysis conducted using the CA-GREET 1.8b model.
According to four months of data provided by AC Transit to back up its application, the electricity requirements for H2 generation and compression (only the portion generated using electrolysis) are between 39% to 71% of total solar electricity generated during the four summer months represented by the data. In other words, under current operating conditions, the facility generates adequate solar electricity to offset all of the energy required for on-site H2 production and compression.
Because of the limited data set, ARB staff is only conditionally approving the application. If AC Transit meets the conditions set forth, it can retain the certified CI and continue to generate LCFS credits. Conditions are:
The company shall provide evidence that generated solar electricity offsets all of the electricity used in on-site H2 production and compression.
The company shall provide quarterly receipts for the next seven quarters to support quantity of H2 produced on-site by electrolysis; energy consumed for electrolysis; H2 procured from external vendor(s); total compression energy at the facility; and total solar electricity production.
AC Transit shall affirm that electricity generated at their solar installations is not used to offset credits under any other program (GHG-based or otherwise).