On the climate impacts of blue hydrogen production

Abstract

Natural gas based hydrogen production with carbon capture and storage is referred to as blue hydrogen. If substantial amounts of CO2 from natural gas reforming are captured and permanently stored, such hydrogen could be a low-carbon energy carrier. However, recent research raises questions about the effective climate impacts of blue hydrogen from a life cycle perspective. Our analysis sheds light on the relevant issues and provides a balanced perspective on the impacts on climate change associated with blue hydrogen. We show that such impacts may indeed vary over large ranges and depend on only a few key parameters: the methane emission rate of the natural gas supply chain, the CO2 removal rate at the hydrogen production plant, and the global warming metric applied. State-of-the-art reforming with high CO2 capture rates combined with natural gas supply featuring low methane emissions does indeed allow for substantial reduction of greenhouse gas emissions compared to both conventional natural gas reforming and direct combustion of natural gas. Under such conditions, blue hydrogen is compatible with low-carbon economies and features climate change impacts in line with green hydrogen from electrolysis supplied with renewable electricity. However, neither current blue nor green hydrogen production pathways render fully “net-zero” hydrogen without additional carbon dioxide removal.

On the cost competitiveness of blue and green hydrogen

“…Considering the entire supply chain, the production of green hydrogen is associated with lower greenhouse gas (GHG) emissions 3 if produced entirely using renewable electricity, while blue hydrogen can be produced at lower costs at least in the near future 4 . The predominant technology for producing hydrogen is steam methane reforming (SMR) of natural gas.…”

“…Enabling higher net (i.e., plant-wide) CO2 capture rates (>90%) in SMR plants requires post-combustion CO2 capture from reforming furnace flue gas, which is more expensive (around 22% more expensive than partial capture) 7 . However, coupling autothermal reforming (ATR) of natural gas with CCS can more cost-efficiently produce low-carbon hydrogen, if in addition methane leakage rates are substantially reduced compared to the current industry standard 3,8 . Today, production costs of blue hydrogen are lower than those of green hydrogen 4,5 .…”

Role of Liquid Hydrogen Carriers in Deeply Decarbonized Energy Systems

“…The multiplicity of technology options across the H 2 supply chain (consisting of production, storage, transport, and end-use) and its potential uses in a low-carbon energy system motivate the use of systems analysis methods, which can incorporate regional context about end uses and resource availability as well as interdependencies with other energy vectors (e.g., electricity and natural gas) to identify the cost-effective and low-emitting supply chain configurations. For instance, while electricity-based H 2 using low-temperature electrolyzers (i.e., power-to-H 2 , P-H 2 ) is often referred as “green hydrogen”, the relatively low renewable penetration and high natural gas penetration in many U.S. regional grids as of 2020 make round-the-clock production of H 2 via grid electricity more CO 2 emitting than natural gas-based steam methane reforming. , Flexible operation of the electrolyzer, that is, producing during times of high variable renewable energy (VRE) generation and shutting down during low VRE generation, however, can not only achieve very low-carbon intensity and use low-marginal cost electricity − but could also provide system-wide benefits by reducing cost of grid decarbonization via VRE penetration. − The relative importance of P-H 2 routes in the H 2 supply chain is also impacted by availability and cost of other low-carbon H 2 production processes, such as natural gas-based steam methane reforming (SMR) and autothermal reforming (ATR) coupled with carbon capture and storage (CCS), integration with nuclear power plants and high temperature electrolyzers, as well as integrated use of electricity and natural gas with CO 2 capture …”