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The energy transition requires technologies to decrease greenhouse gas (GHG) emissions. Different sectors, including agriculture, industry, and transport, deploy hydrogen technologies. The hydrogen color wheel enables us to codify generation technologies. Each color of hydrogen has a distinct production pathway that generates different amounts of greenhouse gas emissions. 

  1. Grey/ Brown/Black hydrogen, produced by burning fossil fuels, primarily natural gas and coal (brown from lignite), causes the emission of up to 20 tons of carbon dioxide per ton of hydrogen. This color pathway accounts for 90 percent of global hydrogen production.
  2. Blue hydrogen, produced by combining gray hydrogen and carbon capture and storage (CCS) and carbon capture, utilization, and sequestration (CCUS), avoids most GHG emissions.
  3. Turquoise hydrogen, produced via the pyrolysis of methane, generates hydrogen and solid carbon.
  4. Green hydrogen, produced from renewable energy sources like bioenergy, solar, and wind, results in zero-emission. It is currently expensive to produce. 
  5. Yellow (or purple) hydrogen, resulting from electrolysis supplied by electricity from nuclear power plants or other electricity sources, could produce higher emissions compared with blue or green hydrogen. 
  6. Pink/ purple/red hydrogen, results from electrolysis supplied by electricity from nuclear power. The carbon intensity score is excellent, with zero carbon emissions associated with this process. However, social, political, and safety concerns impact this production. 
  7. White hydrogen is geological and naturally occurring. However, there are limited ways to harvest and use this potentially CI-friendly form of hydrogen.

 Therein lies a critical challenge for the successful transition to a low-carbon economy. As energy systems increasingly evolve from centralized to decentralized, from “grey” to “green,” stakeholders will need to efficiently account for, and track emissions and green molecules in a transparent, secure, and standardized way and must be able to do so along value chains from production to consumption.

Overall, the rate at which green hydrogen costs decrease will depend on government policies and incentives, such as carbon pricing and tax credits

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