Bill Gates wrote an insightful new blog post: “To cut emissions, use this Swiss Army Knife.”  He explains why hydrogen is essential now, how we might produce it without carbon dioxide, and why it may be more critical in our future. It’s worthwhile reading. My friend Christopher recently talked to me about future uses of hydrogen. Christopher and Bill Gates are both on to a good idea; they triggered me to start thinking more about hydrogen.
When I think about hydrogen, three things spring to mind: Lots of energy, easily made from water and electricity, and very dangerous. These were lessons I learned more than fifty years ago.
The energy available from hydrogen propelled the Apollo moon program. The Saturn V second and third-stage rockets used liquid hydrogen fuel; that was a lot of liquid hydrogen! I found that hydrogen was easy to make in my high school chemistry lab using electrolysis. The collected hydrogen would burn with a bit of pop.
I had seen proof of the dangers of hydrogen. A friend owned a melted piece of structural aluminum from the Hindenburg; this hydrogen-filled dirigible had burned while mooring in 1937. A more memorable use: the hydrogen-oxygen fuel cells on Apollo 13. The explosion of one of these fuel cells almost killed the crew and led to a remarkable space rescue effort.
After reading Bill’s article and talking with my friend about the future of hydrogen, I decided it was time to upgrade my knowledge of hydrogen. I decided upon a four-part plan: How do we make hydrogen today? What are the current applications of hydrogen? How might we use hydrogen in the future? Finally, how would we produce hydrogen in the future? I divided this blog into two. The first part covers hydrogen production and application today; the second will address the future. My goal was to teach myself a bit more about hydrogen, and hopefully, it will interest readers.
So, how do we make industrial quantities of hydrogen today? I found an explanation from the Department of Energy of one method of making hydrogen.  Hydrogen is primarily made via a Steam-Methane Reforming reaction (SMR). Methane gas reacts with steam and heat to produce hydrogen and carbon monoxide:
CH4 + H2O (+ heat) → CO + 3H2
The remaining carbon monoxide reacts with steam in the Water-gas Shift (WGS) reaction. It produces more hydrogen and carbon dioxide:
CO + H2O → CO2 + H2 (+ heat)
Another method used to produce hydrogen is coal gasification.  In this process, oxygen combusts carbon in coal to produce carbon dioxide:
C + O2 → CO2 ( + heat)
The CO2 and heat react (gasification) to produce carbon monoxide:
C + CO2 (+ heat) → 2CO
The Water-gas Shift (WGS) reaction produces hydrogen and carbon dioxide:
CO + H2O → CO2 + H2 (+ heat)
In 2020, the world produced 70 million tons of hydrogen. According to the US Department of Energy, 76% of global hydrogen comes from the Steam-methane reforming reaction, 22% more from coal gasification, and 2% from electrolysis. 
Why change these processes? Bill Gates said that industrial hydrogen manufacture produces 1.6% of CO2 emissions. The International Energy Agency (IEA) estimated that hydrogen generation would generate about 900 million tons of carbon dioxide in 2020.  Hydrogen produced from uncontrolled fossil fuels is referred to as “grey” hydrogen, as defined by researchers at Columbia University. 
I was surprised that petroleum refining is today’s most important use of hydrogen. The hydro-desulfurization reaction lowers the sulfur content of fossil fuels, thus using more than half the world’s hydrogen. The manufacture of ammonium nitrate fertilizer via the Haber process uses lots of hydrogen. Metal refining, chemicals (acid, methanol, hydrogen peroxide), and hydrogenated oil food production also use hydrogen. 
 Gates, Bill. THE OTHER HYDRO POWER: To cut emissions, use this Swiss Army Knife. GatesNotes The Blog of Bill Gates, 21 June 2022. Accessed 22 June 2022.
 US Department of Energy. Hydrogen Production: Natural Gas Reforming. Accessed 22 June 2022. https://www.energy.gov/eere/fuelcells/hydrogen-production-natural-gas-reforming
 Allen, Jessica. Explainer: how do we make hydrogen from coal, and is it really a clean fuel?, The Conversation website, 13 April 2018. Accessed 25 June 2022. https://theconversation.com/explainer-how-do-we-make-hydrogen-from-coal-and-is-it-really-a-clean-fuel-94911
 US Department of Energy. Hydrogen Strategy, July, 2020. Accessed 22 June 2022. https://www.energy.gov/sites/prod/files/2020/07/f76/USDOE_FE_Hydrogen_Strategy_July2020.pdf
 Bermudez, Jose M.; Hannula, Ikulla et. al. Hydrogen – More efforts needed. International Energy Agency, November, 2021. Accessed 25 June 2022. https://www.iea.org/reports/hydrogen
 Ochu, Emeka; Braverman, Sarah; Smith, Griffin; and Friedman, Julio. Hydrogen Fact Sheet: Production of Low-Carbon Hydrogen. Columbia University, 17 June 2021. Accessed 22 June 2022. https://www.energypolicy.columbia.edu/research/article/hydrogen-fact-sheet-production-low-carbon-hydrogen
 Brown, Andy. Uses of Hydrogen in Industry. The Chemical Engineer, 16 July 2019. Accessed 25 June 2022. https://www.thechemicalengineer.com/features/uses-of-hydrogen-in-industry/