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How green can blue hydrogen be?

Ferhani, Yusef D.

Stanford Digital Repository 2022

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  • Título:
    How green can blue hydrogen be?
  • Autor: Ferhani, Yusef D.
  • Assuntos: Carbon Capture and Sequestration ; Carbon dioxide mitigation ; Energy ; Hydrogen
  • Descrição: This report is intended to address some of the confusion surrounding the potential climate impact of blue hydrogen. Today, only a handful of reports have been published that perform life cycle emission analyses of blue hydrogen facilities. The existing reports have conclusions that differ (sometimes drastically) from one another. Rather than these reports having flawed or inconsistent methodologies, the larger reason for the inconsistencies lies in the variety of processes to produce blue hydrogen. Two blue hydrogen facilities can look drastically different from one another. Depending on the type of reforming process (e.g. steam-methane, autothermal), carbon capture location, and capture technology, a blue hydrogen process will look different and have very different parasitic energy demands. Even when a specific blue hydrogen process is defined, the life cycle emission analysis often varies heavily with facility specific factors such as the natural gas supply chain’s leakage rate or the carbon intensity of the grid. There are many degrees of freedom that can change dramatically the carbon intensity of the hydrogen produced. Recognizing that blue hydrogen is too broad of a concept to generalize, this report aims at specifying as many of those degrees of freedom as possible in order to obtain a clear comparison. An effective comparison is between a specific grey hydrogen baseline plant and blue hydrogen plant of a similar size with minimal intrusion to the design of the baseline grey hydrogen plant. This report uses a trustworthy IEAGHG report that supplies comparable grey and blue hydrogen plants with process information supported by robust simulations. The blue hydrogen process from the IEAGHG report was then modified to better understand how utilizing new technology can affect the life cycle emissions of a blue hydrogen process. With three high-confidence plants defined, a comparison of life cycle emissions is performed for the three cases. It was found that the life cycle emissions of blue hydrogen processes can vary significantly depending on the equivalent CO2 emissions of fugitive natural gas leakage rate from the natural gas supply chain. Identical blue hydrogen processes can have upstream emissions tied to the natural gas supply chain that account for 69% to 92% of total life cycle emissions. Consequently, this makes the emissions reduction of blue hydrogen versus grey hydrogen variable. Identical blue hydrogen processes can have life cycle emissions that are ~35% to ~80% less than a comparable grey hydrogen SMR process. The assumptions made in performing a life cycle emission analysis of blue hydrogen is explored. While several factors may have significant results, the assumptions made around the CO2 capture process has the largest impact on the benefit of blue hydrogen over grey. Blue hydrogen facilities with the same reported capture rates can have a difference in life cycle emissions of greater than 47%.
  • Editor: Stanford Digital Repository
  • Data de criação/publicação: 2022
  • Idioma: Inglês
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