Carbon capture in blue hydrogen production is not where it is supposed to be - Evaluating the gap between practical experience and literature estimates

Abstract

Blue hydrogen from natural gas reforming coupled with carbon capture and storage (CCS) is seen as one potential low-emission hydrogen production pathway. Diverging life cycle assessments (LCA) on the greenhouse gas (GHG) emissions of blue hydrogen, however, make its contribution in a future carbon-neutral energy system uncertain. Our objective is to determine how the technical performance of carbon capture (capture rate and energy consumption) in hydrogen production is depicted in literature and how it compares to blue hydrogen plants in practice, thereby gaining insights on how CCS influences the ambiguity around blue hydrogen's decarbonization potential. We first review the recent blue hydrogen LCA literature with a focus on the carbon capture technology. Our results show that energy consumption and sources, as well as the capture rate of CCS differ in the studies, with substantial impact on GHG emissions. We then compare literature results to existing and planned blue hydrogen production plants. None of the existing plants with CCS has the identified process configuration necessary to comply with the European GHG emissions threshold for renewable fuels (28.2 g CO2-eq./MJ H2). Due to non-harmonized assumptions hampering direct comparisons of GHG footprints, we conduct a German case study with harmonized data. It illustrates the impact of the energy balance and its links with upstream supply chains using practice conditions in the near future. Again, most of the evaluated supply chain and process configurations exceed the European GHG emissions threshold. From that we conclude that blue hydrogen's decarbonization potential in the short to medium term is most likely more limited than announced capture rates suggest. Hence, we recommend to establish policies for tracking the decarbonization of upstream and downstream supply chain elements in hydrogen project development, as well as to set regulations for accounting and monitoring of GHG emissions over the entire supply chain.