Hydrogen can be produced using 4 broad process groups: thermal, electrolytic, biological, and solar-driven.
Within each group, multiple forms of technology have been developed. For the map, we have divided the dataset
into these groups. The database and map are intended to be evergreen. As the hydrogen sector develops, the PE
data and maps team will be adding more projects. Most of the current projects indicated on the map
fall into the Thermal and Electrolytic process groups.
Thermal processes for hydrogen production typically involve steam reforming, a high-temperature process in which steam reacts
with a hydrocarbon fuel to produce hydrogen. Many hydrocarbon fuels can be reformed to produce hydrogen, including natural gas,
diesel, renewable liquid fuels, gasified coal, or gasified biomass. According to the IEA, Hydrogen is almost entirely supplied
from natural gas and coal today.
Water can be separated into oxygen and hydrogen through a process called electrolysis. Electrolytic processes take place in
an electrolyser, which functions much like a fuel cell in reverse. Instead of using the energy of a hydrogen molecule like
a fuel cell, an electrolyser creates hydrogen from water molecules.
Biological processes use microbes, such as bacteria and microalgae, to produce hydrogen. In
microbial biomass conversion, the microbes break down organic matter like biomass or wastewater
hydrogen, while in photobiological processes the microbes use sunlight as their energy source.
Solar-driven processes use light as the agent for hydrogen production. Solar-driven processes
include photobiology, photoelectrochemical reactions and solar thermochemical reactions.
processes use the natural photosynthetic activity of bacteria and green algae to produce
hydrogen. Photoelectrochemical processes use specialised semiconductors to separate water into
and oxygen. Solar thermochemical hydrogen production uses concentrated solar power to drive
splitting reactions, often along with other species such as metal oxides.