Factbox: Germany paints hydrogen energy future in green, grey, blue and turquoise

FRANKFURT (Reuters) - Germany’s cabinet passed a national hydrogen strategy on Wednesday as part of a wider push to decarbonize Europe’s largest economy, government sources said.

Sectors such as steelmaking, heating, transportation and chemicals are beginning to develop large-scale hydrogen applications to gradually replace fossil fuels.

Germany ultimately aims to use renewable energy such as wind or solar to power the electrolysis used to extract hydrogen from water.

The government has proposed boosting electrolysis capacity by 5,000 megawatts (MW) by 2030 and adding 10,000 MW by 2040.

Hydrogen falls into four categories denoted by color:

1. Green hydrogen

Derived from renewable sources which could include offshore wind operators developing floating electrolysis plants.

Green hydrogen can be stored, piped, or carried by tankers to consumers, for example to serve hydrogen filling stations.

Hydrogen can also be turned into synthetic methane with qualities identical to natural gas, but this process is at an early stage.

Biomethane derived from fermented crops can also play a role.

2. Grey hydrogen

Using steam-methane reforming, currently the standard industry process, it involves extracting hydrogen from fossil fuels such as coal or gas while releasing carbon monoxide and carbon dioxide.

3. Blue hydrogen

Blue hydrogen is grey hydrogen but separates the CO2 emissions for re-use or underground or subsea storage. Seen as a transitional approach while demand cannot be met fully by green hydrogen, some environmentalists oppose this option.

4. Turquoise hydrogen

Also called low-carbon hydrogen and so far very small scale, this is hydrogen generated from natural gas but using pyrolysis where the gas is passed through molten metal, producing solid carbon as a byproduct with useful applications.

Reporting by Vera Eckert; editing by Jason Neely