Hydrogen is the simplest element, and the most abundant substance in the universe.
When hydrogen burns, it generates energy in the form of heat, with water as a by-product.
That means energy created from hydrogen generates no atmosphere-warming carbon
dioxide, making it one of many potential energy sources that could help reduce carbon
emissions and slow global warming.
But creating hydrogen and transforming it into a useful format requires energy — and that
energy is not necessarily renewable. That process is also inefficient and expensive
compared with other forms of energy, renewable or not. Many critics say the hydrogen
industry a way for oil and gas giants to stall the adoption of pure renewable energy sources
like solar and wind, giving them a “green” cover while still maintaining demand for their
products.
What is green hydrogen, blue hydrogen, and so on?
Producing hydrogen takes energy because hydrogen atoms don’t exist on their own — they
are almost always stuck to another atom, often another element. (On earth, hydrogen is
particularly abundant in the form of water, or H2O.) Creating pure hydrogen requires
breaking those molecular bonds.
In the energy business, people refer to hydrogen by an array of colours to as shorthand for
how it was created.
One may of making hydrogen is a process called electrolysis, when electricity is passed
through a substance to force a chemical change — in this case, splitting H2O into hydrogen
and oxygen.
Green hydrogen is when the energy used to power electrolysis comes from renewable
sources like wind, water or solar.
Blue hydrogen is hydrogen produced from natural gas with a process of steam methane
reforming, where natural gas is mixed with very hot steam and a catalyst. A chemical
reaction occurs creating hydrogen and carbon monoxide. Water is added to that mixture,
turning the carbon monoxide into carbon dioxide and more hydrogen. If the carbon dioxide
emissions are then captured and stored underground, the process is considered carbon-
neutral, and the resulting hydrogen is called “blue hydrogen.”
But there’s some controversy over blue hydrogen because natural gas production inevitably
results in methane emissions from so-called fugitive leaks, which are leaks of methane from
the drilling, extraction and transportation process.
Methane does not last in the atmosphere as long as carbon dioxide, but it is much more
potent as a greenhouse gas. Over 100 years, one ton of methane can be considered to be
equivalent to 28 to 36 tons of carbon dioxide, according to the International Energy Agency.
Grey hydrogen is made from natural gas reforming like blue hydrogen, but without any
efforts to capture carbon dioxide by-products.
Pink hydrogen is hydrogen made with electrolysis powered by nuclear energy, which does
not produce any carbon dioxide emissions. (Although nuclear energy creates radioactive
waste which must be stored safely for thousands of years.)
Yellow hydrogen is hydrogen made with electrolysis from the energy grid. The carbon
emissions vary greatly depending on the sources powering the grid.
Turquoise hydrogen is hydrogen produced from methane pyrolysis, or splitting methane
into hydrogen and solid carbon with heat in reactors or blast furnaces. Turquoise hydrogen is
still in its nascent stages of being commercialized, and its climate-conscious value depends
on powering the pyrolysis with clean energy and storing the physical carbon.
The colour system is a bit simplistic and needs to be updated and made more specific,
said Daryl Wilson, the executive director of the coalition of the Hydrogen Council, an
organization of industry CEOs.
“The colour scheme is not helpful in in the sense that it’s not getting to the key point, which is
what are the environmental attributes of the hydrogen being produced,” Wilson told CNBC.
“The key issue is there has to be a methodology for tracking and declaring the specific CO²
intensity of whatever hydrogen you’re working with.”
