Carbon-Negative Hydrogen from Ethanol via Catalytic Oxidative Reforming

This study evaluated a commercial technology for producing low- or negative-carbon hydrogen through ethanol catalytic oxidative reforming, focusing on the life cycle greenhouse gas emissions, or carbon intensity (CI). Various scenarios were analyzed: (a) comparing corn ethanol (first-generation or Gen1 ethanol) and cellulosic ethanol (second-generation or Gen2 ethanol) as feedstocks; (b) assessing carbon capture and sequestration (CCS) for CO2 from upstream fermentation; and (c) evaluating oxygen sourcing via air separation units vs. on-site or off-site water electrolysis using a proton exchange membrane. Findings indicate that the CI for hydrogen production using Gen2 ethanol from corn stover is lower than that of Gen1 corn ethanol. Additionally, using proton exchange membrane-generated oxygen results in a lower CI than air separation unit-generated oxygen, regardless of the sourcing method. Implementing CCS for the hydrogen production plant's evolved CO2 is essential for achieving a net-negative CI for hydrogen from Gen1 ethanol. All examined scenarios, including both ethanol generations, oxygen sources, and CCS applications, demonstrated a net-negative carbon intensity, surpassing the life cycle greenhouse gas emissions threshold of 0.45 kg CO2e/kg to enable policy credits as outlined in the Inflation Reduction Act Section 45V. In comparison, the CI for hydrogen from steam methane reforming stands at 3.4 kg CO2e/kg with CCS and 9.4 kg CO2e/kg without CCS.