Is Hydrogen Energy Sustainable, Renewable & Clean?

In this guide, we look at whether hydrogen energy is sustainable, renewable and clean.

We consider how hydrogen energy might rate in different ways across each of these three measures.


First, What Is Hydrogen, & How Is It Produced?

This separate guide outlines what hydrogen is, & also how it’s produced


Hydrogen Production vs Using Hydrogen As Energy

The production of hydrogen and the use of hydrogen are two separate steps.


Hydrogen Production

Hydrogen cannot be extracted directly from nature, so hydrogen first has to be produced before it can be used for hydrogen energy

The vast majority of hydrogen is produced right now from the reforming of fossil fuels, with natural gas being the main fossil fuel used


The Use Of Hydrogen

When hydrogen is used for energy in a fuel cell, it combines with oxygen or reacts with oxygen, in a hydrogen fuel cell, and the by-products are energy and water vapor (H20)

Although, mentions that ‘… when atmospheric air is used instead of pure oxygen, a small amount of nitrogen oxide [which contributes to air pollution] may be released’


Comparing The Above Two Stages

It appears that no matter how hydrogen is produced – from fossil fuels or from water (which uses electricity for electrolysis), the hydrogen usage stage might always be more clean and sustainable.


Now, moving on to look at how sustainable, renewable and clean hydrogen energy might be …


Examples Of How Hydrogen Might Not Be Sustainable

Some of the ways hydrogen might be less sustainable might be:


– When Hydrogen Is Produced From Fossil Fuels

Producing hydrogen from fossil fuels like natural gas or even coal has a carbon footprint, and that’s currently where most of the hydrogen we produce comes from.

Steam methane reforming from natural gas in particular releases carbon and other pollutants.

Some reports indicate that the amount of carbon that hydrogen production releases per year is significant.


[Conventional hydrogen production using natural gas or other hydrocarbons emits carbon dioxide] (


Steam-methane reforming … [which] extracts hydrogen from methane [has a] reaction [which] releases fossil carbon dioxide and carbon monoxide into the atmosphere which are greenhouse gases …(


 … production of hydrogen is responsible for CO2 emissions of around 830 million tonnes of carbon dioxide per year, equivalent to the CO2 emissions of the United Kingdom and Indonesia combined (


Examples Of How Hydrogen Might Contribute To Sustainability

Some of the ways hydrogen might contribute to sustainability might be:


– Using Electrolysis For Hydrogen Production Over Reforming Of Hydrocarbons

Electrolysis may be a more efficient process than reforming.

Efficiency is a factor that can impact sustainability.


[The efficiency of electrolysis is greater than methane steam reforming, at 70-80% compared to 60-75%] (


– Using Cleaner Energy For The Electricity Used In Electrolysis In Hydrogen Production

Where electrolysis is used for hydrogen production, there might be sustainability benefits if cleaner energy sources like renewables or nuclear are used, and also if sustainably sourced water is used.

Hydrogen produced with renewables like solar or wind is referred to as green energy


– Using Hydrogen & Fuel Cells In Some Specific Applications

Using hydrogen and fuel cells that use hydrogen may generally help reduce emissions for some specific applications.

One application where this might be the case might be for some types of vehicles.


Due to their high efficiency and zero-or near zero-emissions operation, hydrogen and fuel cells have the potential to reduce greenhouse gas emission in many applications (


The resource in the resources list outlines how hydrogen helps decrease emissions across different uses such as light-duty highway vehicles, specialty vehicles, transit buses, auxiliary power units, and combined heat and power (CHP) systems


– Mixing Hydrogen With Natural Gas In Gas Pipes

Mixing small shares of hydrogen with natural gas may help reduce CO2 emission for some activities 


 … the addition of 20% of hydrogen (an optimal share that does not affect gas pipes and appliances) to natural gas can reduce CO2 emissions caused by heating and cooking (


– Converting An Engine To Run On A Hydrogen Mix

Converting some types of vehicle engines to run on a hydrogen mix may help reduce emissions

Although, this might be restricted to only prototypes at the moment


Alongside mono-fuel hydrogen combustion, combustion engines in commercial vehicles have the potential to be converted to run on a hydrogen-diesel mix [and some prototypes have shown] up to 70% of CO2 emissions [reduction] during normal driving conditions (


‘Brown’, ‘Green’, ‘Blue’, & ‘Grey’ Hydrogen 

Both and mention the phrases brown, green, blue and grey hydrogen.

Below is our paraphrased summary of each of those terms:


Brown Hydrogen

Is hydrogen that is produced from fossil fuels

Most of the hydrogen humans produce is currently produced from natural gas via the steam methane reformation process

But, the coal gasification method can be used too

So, brown hydrogen might come from both natural gas and coal 


Green Hydrogen

Green hydrogen may mainly come from the electrolysis of water (i.e. running an electrical current across the water to separate the hydrogen and oxygen atoms)

‘Green hydrogen’ might specifically involve using renewable energy sources (like solar or wind) for the electricity used in electrolysis, and also sustainable water sources for the water

Read more about green hydrogen in this guide


Blue Hydrogen

Blue hydrogen captures the CO2 from the hydrogen production process, and then stores it via CCS (i.e. carbon capture storage)


Grey Hydrogen

Is hydrogen that is produced as a by-product of an industrial process instead of it’s own dedicated hydrogen production process


So, Is Hydrogen Energy Sustainable, Renewable & Clean

Production Of Hydrogen

How sustainable, renewable and clean hydrogen energy is depends in large part on how the hydrogen is produced.

The production of hydrogen energy might be more sustainable, renewable or clean if it uses electrolysis of water to produce hydrogen instead of producing hydrogen from hydrocarbons/fossil fuels like natural gas

Using cleaner energy sources for the electricity, and sustainably sourced water might be some ways to make it more sustainable, renewable and clean.

Producing hydrogen from hydrocarbons might be less sustainable, renewable and clean because it relies on scarce fossil fuel resources, there’s a carbon footprint to consider, and potentially air pollutants too.


Use Of Hydrogen

In terms of the use of hydrogen, it might be more sustainable, renewable and clean than some other energy sources and fuels for some applications.

One example of this might be using hydrogen in vehicles compared to burning gasoline or diesel.

The use of hydrogen fuel cells in some vehicles may be one example of this, however, the production footprint also needs to be included to get an accurate view of the total lifecycle sustainability of using hydrogen.


Comparing Hydrogen To Other Energy Sources

The energy sources being compared to hydrogen energy matter in determining whether hydrogen is sustainable, renewable or clean.

Comparing hydrogen to conventional fossil fuel energy may make hydrogen look greener in some ways than comparing it to some types of renewable energy sources, and nuclear.












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