There are three main types of hydrogen production currently possible, each with their own environmental impacts.
The first type, called ‘grey’ hydrogen, is produced by steam reforming and makes up around 95% of the hydrogen used today. This process usually involves separating hydrogen atoms from carbon atoms in methane, but it releases the greenhouse gasses carbon monoxide and a small amount of carbon dioxide, which contribute to global warming. Aside from methane, other fossil fuels like propane, gasoline or coal can be used in steam reforming to produce pure hydrogen. It is estimated that grey hydrogen production releases 830 million metric tons of CO2 each year.
‘Blue’ hydrogen, also called decarbonised hydrogen, uses carbon capture and storage to remove the CO2 that is produced from the steam reforming process.
The third method, ‘green’ or renewable hydrogen is made through the electrolysis of water. When the electrolysis is done using renewables, it leaves nothing but oxygen as a by-product, making it a genuinely clean energy source. Electrolysis uses an electric current to split water into hydrogen and oxygen. When the electric current in the electrolyser is produced using renewable power, like wind or solar, it creates a pollutant-free energy source. As the cost of renewable energy reduces, so the interest in green hydrogen is increasing.
There are other methods of hydrogen production being explored currently too, with ‘turquoise’ hydrogen being one of the most promising currently. This technique involves thermally cracking natural gas into hydrogen and solid carbon, meaning there is no requirement for CCS. This technique uses molten metal pyrolysis and produces desirable natural graphite rather than CO2. Despite the promise of this method, the technology is still in its infancy.
As mentioned above, unlike other energy sources, hydrogen does not exist freely in nature and so it needs to be produced. The method of production determines how much of an environmental benefit hydrogen fuel can deliver.
Focusing on the cleanest of the hydrogen production techniques, for green hydrogen, there are a great many environmental advantages to this energy source:
- Plentiful Supply: Hydrogen is the most abundant element in the universe, making it virtually limitless
- Transportable: Hydrogen can be used where it is produced or transported to where it is needed elsewhere
- Excellent Storage Properties: Unlike batteries, which cannot hold large quantities of electricity for extended time periods, hydrogen can be stored for a long time until it is needed
- Uses Excess Renewable Energy: Hydrogen can be produced using the excess energy from renewable sources such as wind farms, meaning this energy does not go to waste and is instead ‘converted’ into hydrogen that can be stored
- More Energy Efficient than Fossil Fuels: Hydrogen contains nearly three times as much energy as fossil fuels, making it more energy efficient
- Readily Available: Because green hydrogen can be produced wherever there is water and electricity to generate more heat and electricity, it is readily available for production
- Fuel Cells: Hydrogen fuel cells offer a wide range of additional advantages, including energy efficiency improvements, portability and fast refuelling times for environmentally-friendly vehicles – you can see more about these, below.
While hydrogen can be stored in existing gas pipelines and used to power industry and domestic appliances it can also be used with fuel cells to power anything that uses electricity.
However, fuel cells don’t run down or need to be recharged, as with batteries, so long as they are provided with hydrogen fuel. This allows them to be used to power vehicles, offering zero emissions as well as being two to three times as efficient as the petrol-powered internal combustion engine. In addition, unlike with batteries, vehicle refuelling takes an average of less than four minutes.
Fuel cells also function independently from the grid, meaning that they can be used in disaster zones or military settings as independent heat or electricity generators that can even be connected to the grid to provide reliable and consistent power.
You can find out more about hydrogen fuel cells and how they work in this FAQ.
Despite the many advantages offered by hydrogen, there are still a number of challenges to be considered:
Safety
Hydrogen is more flammable in the air than petrol, natural gas or propane. This has led to concerns over the safety of hydrogen as a fuel, particularly for vehicles or when being transported or stored. However, at lower concentrations, hydrogen has a similar flammability potential as other fuels. This is aided by the fact that hydrogen is so light that it quickly disperses into the atmosphere once released into the air, preventing it from igniting.
Storage
While it is possible to store hydrogen, it can be a challenge for some applications. Because of its low energy content by volume, it needs to be stored at high pressures, low temperatures or with chemical processes that will compact it. This becomes a particular concern with lighter vehicles that have a more limited size and weight capacity for fuel storage. It takes between 5 and 13 kilograms of compressed hydrogen gas to reach a 300 mile driving range, which requires a larger storage tank at higher pressures than with other gaseous fuels.
Transportation
The low density of hydrogen also makes it a challenge to transport, requiring either liquefying at -253˚C or compressing as a gas to 700 times atmospheric pressure. As a result, hydrogen is currently transported in trucks with low-temperature tanks, pressurised trailers, by rail, barge or through dedicated pipelines for gaseous hydrogen. Existing natural gas pipelines are also used to transport smaller quantities of hydrogen of less than 5-10% blended with the natural gas. Pure hydrogen can make steel pipes and welds brittle, leading to cracking.
Infrastructure
For widespread hydrogen fuel cell use in vehicles, there would also need to be investment in infrastructure to support users, such as refuelling stations.
Cost of Production
The cost of fuel cell technology and productionis also currently a challenge for green hydrogen use. The most expensive part of a fuel cell’s production is manufacture of the fuel cell stack, while the use of platinum in the anode and cathode as the catalyst to split hydrogen also adds extra cost. Research is currently ongoing to find more efficient and cheaper manufacturing methods and materials without compromising performance. Costing around three times as much as natural gas, and being more expensive than grey or blue hydrogen due to the cost of electrolysis, there needs to be a concerted effort to bring down the cost of green hydrogen.
Despite the challenges associated with green hydrogen, it looks set to become an important part of the move towards climate neutrality. Included in all eight of the European Commission’s ‘Net Zero’ emissions plans for 2050, hydrogen can store surplus power from renewables, decarbonise sectors including long-distance transport and heavy industry, and replace fossil fuels as a zero-carbon feedstock for fuel and chemical production.
Europe is leading the way for green hydrogen, not just for the environmental benefits such as reducing greenhouse gas emissions, but also in the creation of a hydrogen economy as part of the EU’s post-COVID economic recovery, under the European Green Deal for the continent to become the world’s first to achieve climate neutrality by 2050. To achieve this, there will need to be a complete phasing out of fossil fuel use and an 80-95% reduction in emissions by 2050.
The United States are also investigating green hydrogen, as the U.S. Department of Energy invests millions into researching hydrogen fuel cells, while Australia, Chile, Germany, Japan and Saudi Arabia are also investing in green hydrogen.
It is believed that green hydrogen power will be one component in a wider mix of solutions to combat climate change, including improved energy efficiency, renewables and direct electrification. This is especially true of areas such as aviation, shipping, long-distance trucking and concrete and steel manufacturing, which all have requirements for high energy density fuel or intense heat, making them difficult to decarbonise.
Experts believe that green hydrogen use will increase over the coming decade, but the limits of the existing infrastructure will soon be reached. Increasing the infrastructure to the required capacity fast enough could also prove a challenge without the required policy changes to support the market growth. Of course, if managed correctly, growing the hydrogen economy could generate money and support thousands of jobs over the coming years.
The global future of green hydrogen is dependent of the level of investment from manufacturers, fuelling station and infrastructure developers, energy companies, and governments.
If produced in an environmentally-friendly manner, hydrogen can act as part of a wider solution to address climate change. As a zero-emission energy source, green hydrogen also delivers the additional benefit of being able to store unused energy from renewable resources, while being a virtually limitless resource in itself.
However, to use hydrogen as part of the means to achieve net zero will require further investment into research and infrastructure to close the gap and make it a truly viable solution for decarbonisation and slowing climate change.
This investment is underway, particularly across Europe so, hopefully, the wider use of green hydrogen is not too far into the future.
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