- Yellow hydrogen refers to hydrogen gas (H₂) that is produced through electrolysis of water using electricity derived from the conventional power grid, which is typically a mix of energy sources—including fossil fuels (like coal and natural gas), nuclear power, and renewables (such as solar and wind). Unlike green hydrogen, which is specifically produced using 100% renewable electricity, yellow hydrogen lacks a strictly renewable origin, making it a less environmentally friendly option, but often a more accessible or cost-effective one in regions where clean electricity infrastructure is still developing.
- The process of making yellow hydrogen involves electrolysis, where water (H₂O) is split into hydrogen and oxygen using an electric current:
- 2H₂O → 2H₂ + O₂
- Electrolyzers can operate using any electricity source, so if the electricity comes from a mixed or non-renewable grid, the hydrogen produced is classified as yellow. This distinguishes it from green hydrogen (renewables only) and pink hydrogen (nuclear-powered electrolysis).
- The environmental impact of yellow hydrogen varies depending on the carbon intensity of the grid in the specific region. In countries where electricity is primarily sourced from coal or natural gas, the carbon footprint of yellow hydrogen can be high, potentially approaching that of grey hydrogen. However, in regions with a cleaner energy mix—such as those with a significant share of nuclear, hydro, or intermittent renewables—yellow hydrogen can be considerably less carbon-intensive. This variability makes yellow hydrogen a transitional technology, particularly valuable in areas where the grid is decarbonizing but not yet fully green.
- One of the advantages of yellow hydrogen is its flexibility. Because it draws from the grid, production can occur almost anywhere with sufficient infrastructure, without needing dedicated renewable energy installations. It can also serve as a stepping stone toward green hydrogen by utilizing existing electrolyzer technologies and infrastructure, while the energy grid continues to shift toward renewables.
- On the economic side, yellow hydrogen benefits from the falling costs of electrolyzer technologies and the potential to operate during off-peak hours when grid electricity is cheaper or underutilized. Some strategies involve dynamic pricing and smart grid integration, where electrolysis is ramped up when electricity demand is low or when renewable energy surpluses are available, even within a mixed grid.
- However, critics argue that unless the electricity mix is predominantly low-carbon, yellow hydrogen risks being greenwashed—portrayed as clean while still tied to fossil-fuel-based emissions. To ensure true sustainability, it must either be coupled with low-emission electricity sources or transitioned toward greener power over time.
