Research Triangle Energy Consortium

For the longest time blue had been content as a pure spectrum color at a nominal wavelength of 450 nm. Then the hydrogen police said it was not green enough. This despite Kermit the Frog informing us that it was not easy being green. Apparently, Britain agrees with Kermit, as reported in an Economist story. Their hydrogen strategy is heavily loaded with blue.

First a reminder on definitions. When hydrogen is synthesized by reacting methane with water, the process known as steam methane reforming, it is classified as grey hydrogen. If the resultant CO₂ is captured and stored, the color of the hydrogen turns blue. If the hydrogen is produced from splitting water electrolytically using green electricity, it is classified as green hydrogen. To confuse matters further, the Government of India has classified the blue hydrogen from methane reforming as green if the methane is biogas sourced.

Going back to the Economist story, Britain has called for hydrogen to be 4% of energy demand by 2030. Even at this relatively modest target, the green electricity required for this hydrogen to be green would be 126 TWh (terawatt hours). This compares to the total green electricity production in 2020 of 135 TWh, with many potential uses beyond electrolytic hydrogen. In fact, one of the uses planned is blending hydrogen to a 20% level in natural gas pipelines. Mainland Europe has been piloting this and there is a consensus that a 20% blend is tolerated by the pipelines and by the end use.

The British plan calls for production of blue hydrogen in two locations with industry such as ammonia and methanol production that already uses grey hydrogen. Carbon mitigation in industry takes two forms. One is to change the process by replacing the existing reactant, such as coke, with hydrogen, thus curbing or eliminating CO2 emissions. One such is ironmaking with the Direct Reduction Iron process, and the resulting steel would be considered green steel if the hydrogen were to be green. Steelmaking is specifically cited by the British plan.

The other approach is to not change the process, but simply substitute a zero-carbon hydrogen for the grey hydrogen. The British plan favors blue hydrogen as a pragmatic means to achieve carbon mitigation faster than may be possible with just green hydrogen. This plan relies on economical means for capturing and storing the CO2 from the methane reforming. This is increasingly a reasonable expectation, with technology already commercial and likely to be available at scale within a couple of years. Economical is defined as fully loaded cost lower than the carbon penalty in force at the time. This is variable and stands at about €85 at this writing (see figure). A leading carbon capture technology claims capture costs at USD 40 per tonne, with an expected reduction to USD 30 over time. Given that geologic storage costs about USD 10 per tonne, the combined figure is well below the carbon penalty.

The Good Before the Great

Few would dispute that the most desirable hydrogen is the green variety. Here too a relaxation must be sought for the strict definition. The electricity source ought to be expanded from renewable to carbon-free. The carbon mitigation purpose is served and scalable carbon-free sources such as geothermal energy and nuclear power are then comfortably included. As previously discussed, these are excellent fillers of the diurnal and seasonal gaps in solar and wind production.

But green electricity is in short supply compared to the demand. The primary reason is that the largest sources, solar and wind, have low capacity utilization. On the demand side, everybody wants some. The MIT spinout Boston Metals needs it to make electrolytic green steel. The other principal green steel method, DRI, needs electrolytic (green) hydrogen. Data centers supporting the cloud are energy hogs that are growing steeply. All the major players in that space want green electricity. Ditto for bitcoin that other fast growing energy intensive sector. In other words, relatively sparse green electricity has many calls on it.

Enter blue hydrogen. The case against it begins with the fact that only 90 to 95% of the CO2 is captured at the point source. Some is still released. The other knock on it is that natural gas production is implicitly encouraged. But the uncomfortable truth is that every new solar/wind emplacement already creates demand for natural gas to fill the longer duration gaps in output. Although coal and oil will continue to decline, natural gas will be needed as a gap filler till the zero-carbon alternatives hit their stride; and that is a decade or more away. That is plain and simple pragmatism. As is the need for blue hydrogen until green electricity becomes more easily available. It is the only viable near-zero-carbon hydrogen that can achieve scale swiftly.

The battle against climate change must be joined with the best weapons at hand. No active battlefront waits on the ultimate weapon. Blue ought to be the primary color of hydrogen until, again quoting Kermit*, being green is easier.

Vikram Rao

* It’s not easy bein’ green Kermit the Frog, written by Joe Raposo, sung by Jim Henson (1970)