By
Grace Smoot

Hydrogen (H₂) fuel is a clean-burning, zero-emission fuel that many believe could play a substantial role in combating climate change. But H₂ is only as clean as the mechanisms used to produce it. So we had to ask: What is the carbon footprint of hydrogen fuel?

Hydrogen (H₂) has the lowest carbon footprint possible of all fuels. One gallon of H₂ emits 0 pounds of CO₂ when combusted, and driving one mile on average emits 0 grams of CO₂. It combats climate change and has various environmental benefits. However, the method of H₂ production can still produce emissions.

Keep reading to learn about the overall carbon footprint of H₂, its carbon footprint throughout its life-cycle, and how environmentally friendly it is.

Here’s What the Carbon Footprint of Hydrogen Fuel Is

The carbon footprint is one of the ways we measure the effects of human-induced global climate change. It primarily focuses on the GHG emissions associated with consumption, but also includes other emissions such as methane (CH₄), nitrous oxide, and chlorofluorocarbons.

“Carbon footprint: the amount of greenhouse gases and specifically carbon dioxide emitted by something (such as a person’s activities or a product’s manufacture and transport) during a given period”

Merriam Webster

Basically, it is the amount of carbon emitted by an activity or an organization. This includes GHG emissions from fuel that we burn directly (e.g., heating a home, driving a car) and GHG emissions from manufacturing the products that we use (e.g., power plants, factories, and landfills).

Hydrogen (H₂) is a colorless, odorless, tasteless, flammable gas and is the most abundant element in the universe. Although it only makes up 0.14% of the earth’s crust by weight, it is abundant in our oceans, ice packs, rivers, lakes, animal tissue, vegetable tissue, petroleum, and in the atmosphere. The energy stored in H₂ gas can even be used as fuel in various modes of transportation. 

“Hydrogen: a chemical element that is the lightest gas, has no color, taste, or smell, and combines with oxygen to form water”

Cambridge Dictionary

Vehicles that are powered by H₂ are called fuel cell electric vehicles (FCEV). Because they only emit water and warm air, they are considered clean-burning, zero-emission vehicles. In FCEVs, the energy stored in H₂ is converted to electricity by a fuel cell.

The most common type of vehicle fuel cell is the polymer electrolyte membrane (PEM) fuel cell. In this fuel cell, an electrolyte membrane sits between a positive electrode (cathode) and a negative electrode (anode). When oxygen (O₂) and H₂ are introduced into the cell, H₂ breaks apart into protons and electrons. The protons travel through the membrane to the cathode whereas the electrons travel through an external circuit to provide power to the car. The electrons then recombine with the protons and O₂ at the anode to form water, the byproduct of FCEVs.

H₂ fuel is considered clean-burning and has zero emissions. Gasoline and diesel fuel emit 19.59 and 22.44 pounds (lb) of carbon dioxide (CO₂), respectively, per gallon upon combustion. But H₂ fuel emits 0 lb of CO₂ per gallon. The only emissions generated from H₂ fuel come from the production and transportation of H₂ fuel. Because 2.2 pounds of H₂ have the same amount of energy as 1 pound of gasoline, more H₂ is required to drive the same distance.

Burning of hydrogen fuel	Carbon footprint
Burning one gallon	0 grams (g) of CO2 emitted
Driving one mile (on average)	0 grams of CO2 emitted
Per million British thermal units (Btu)	0 pounds of CO2 emitted

H₂ fuel still comes with emissions, albeit not directly. Sourcing H₂ from NG produces approximately 830 million tons of CO₂ every year, which is equivalent to the emissions of the United Kingdom and Indonesia combined. (But more about that below, in the life-cycle assessment.)

Oil (including gasoline and diesel fuel) is the world’s primary fuel source for transportation. But since the turn of the century, there has been a push towards cleaner-burning transportation fuels with fewer negative effects on the environment. 

Establishing H₂ as a mainstream transportation fuel has been difficult and expensive. To date, H₂ makes up less than 0.01% of all energy consumed. Although there were 40,000 FCEVs on the road in June of 2021, this totaled less than 0.01% of global total vehicles and less than 0.03% of total electric vehicles. But spurred by developments in the United States and in Asia, the H₂ fuel market is expected to increase from $651.9 million in 2018 to $42,038.9 million, by 2026.

To understand the total carbon footprint of H₂ fuel, we must assess its life-cycle and each stage’s carbon footprint. This life-cycle assessment (LCA) is a method to evaluate the environmental impacts of products and materials. Over the years, companies have strategically used LCA to research and create more sustainable products. So, let’s have a look at the LCA of H₂ fuel!

The life-cycle stages of hydrogen fuel	Each stage’s carbon footprint
Building of steam-methane reforming plants	CO2 emissions from building the components of the steam-methane reforming plants
Extracting of hydrogen fuel	CO2 emissions from thermal, electrolytic, solar-driven, and biological processes
Transportation of hydrogen fuel	CO2 emissions from transporting H2 by barges, tankers, pipelines, trucks, and railroads across distances
Building back of steam-methane reforming plants	CO2 emissions from utilizing construction equipment to demolish the buildings and construct new buildings in the old steam-methane reforming plants’ place

The total carbon footprint of H₂ fuel would equal the carbon footprint from building + the carbon footprint from extracting + the carbon footprint from transportation + the carbon footprint from building back. 

What Is the Carbon Footprint of Building Hydrogen Steam-Methane Reforming Plants

The main way of producing H₂ is from NG in steam-methane reforming plants. These plants have many components, and constructing these components requires machinery that emits CO₂. 

Sourcing H₂ from NG produces approximately 830 million tons of CO₂ every year, which is equivalent to the emissions of the United Kingdom and Indonesia combined. NG is currently the top provider of H₂, and 7.5 billion tons of CO₂ every year occur because of NG combustion. 

Although the CO₂ emissions from the combustion of NG are about 50%-60% less than those from coal and oil, the primary component of NG is CH₄, a gas 34 times stronger at trapping heat than CO₂ over 100 years. This means that a little CH₄ can go a long way when contributing to global warming.

What Is the Carbon Footprint of Extracting Hydrogen Fuel

H₂ fuel can be produced via the following 4 processes:

1. Thermal processes: In the process of steam reforming, steam reacts with a hydrocarbon fuel to produce H₂. Natural gas, diesel, renewable liquid fuels, gasified coal, or gasified biomass are all hydrocarbons that can be used to produce H₂. Today, approximately 95% of all H₂ is produced from NG steam reforming. 

2. Electrolytic processes: In the process of electrolysis, water is separated into H₂ and O₂ by an electrolyzer. Electrolyzers function in the opposite manner as fuel cells. Instead of using the energy of a H₂ molecule, it creates H₂ from water molecules.

3. Solar-driven processes: In either the photobiological, photoelectrochemical, or solar thermochemical process, light is used to produce H₂. Depending on the specific process, bacteria, semiconductors, or concentrated solar power separate water into H₂ and O₂.

4. Biological processes: In this process, microbes (i.e. bacteria and microalgae) break down organic matter (i.e. wastewater and biomass) to produce H₂.

Almost all of the H₂ produced today comes from NG. This H₂ is referred to as gray hydrogen. In NG steam-methane reforming, high-temperature steam is used to produce H₂ from a methane source, like natural gas. Methane reacts with steam under high pressure in the presence of a catalyst to produce H₂, carbon monoxide, and a small amount of CO₂. This process is endothermic, meaning it requires heat for the reaction to take place. In the following water-gas shift reaction, carbon monoxide and steam react together with a catalyst to produce CO₂ and more H₂. In the last step, pressure-swing absorption, CO₂ and other impurities are removed from the gas, resulting in a pure H₂ gas stream.

What Is the Carbon Footprint of Transportation of Hydrogen Fuel

H₂ is currently distributed via three methods:

1. Pipeline: The least expensive method of H₂ delivery. There are currently 5,000 kilometers of H₂ pipeline in the world, and more than 90% are located in the United States and Germany.

2. High-pressure tube trailers: H₂ is compressed and transported by truck, rail, ship, or barge across distances of 200 miles or less, because this method is expensive. 

3. Liquefied H₂ tankers: In the process of cryogenic liquefaction, H₂ is cooled from a gas into a liquid, enabling H₂ to be transported more efficiently across long distances by truck, rail, ship, or barge. This method must match the rate of H₂ delivery and consumption because liquid H₂ will evaporate if not used at a high rate.

Calculating the carbon footprint of H₂ fuel transportation involves knowing where the H₂ fuel is produced, where it is being consumed, and the distance between the two. Few countries currently produce and transport H₂ fuel, but a handful do currently have production capacities.

In 2020, ten governments adopted H₂ strategies: Canada, Chile, France, Germany, the Netherlands, Norway, Portugal, Russia, Spain and the European Union. And in 2021, four more joined the mix: Czech Republic, Colombia, Hungary, and the United Kingdom. 

The carbon footprint of transportation between countries such as the United States and Germany would be high because of the long transportation distance (7,882 kilometers or 4,898 miles) and multiple modes of transportation required. On the other hand, if H₂ fuel is produced in one country and consumed in that same country, the transportation distance is much shorter and would require fewer modes of transportation, leading to a lower carbon footprint for this stage. 

Essentially, the longer the transportation distance, the higher the carbon footprint. And the higher the carbon footprint for this, the worse effect it has on the environment. 

What Is the Carbon Footprint of Building Back Hydrogen Steam-Methane Reforming Plants

The first FCEV in the United States was only introduced in 2014. Because H₂ fuel technology is relatively new and not currently operational on a global scale, there is not much historical data on its life expectancy. CO₂ emissions at this stage would occur when utilizing construction equipment to demolish the H₂ power plants and construct new buildings in the power plants’ place.

What Role Does Hydrogen Fuel Play in Combating Climate Change

Because H₂ combustion produces only water and warm air as a byproduct, it has the potential to reduce the 36 billion tons (bt) of CO₂ that are emitted every year from burning fossil fuels.

“Climate Change: changes in the world’s weather, in particular the fact that it is believed to be getting warmer as a result of human activity increasing the level of carbon dioxide in the atmosphere:”

Cambridge Dictionary

Climate change is arguably the most severe, long-term, global impact of fossil fuel combustion. Every year, approximately 36 bt of CO₂ are emitted from burning fossil fuels. The carbon found in gasoline reacts with O₂2 in the air to produce CO₂ which warms the earth by acting as a heating blanket.

Reduced CO₂ emissions from H₂ combat climate change in the following ways:

• Increasing temperatures: Earth’s atmosphere has warmed 1.5℃ since 1880. This may not seem like a lot, but these degrees create regional and seasonal temperature extremes, reduce sea ice, intensify rainfall and drought severity, and change habitat ranges for plants and animals.

• Rising sea levels: Global sea levels have increased approximately 8-9 inches since 1880, displacing people living along coastlines and destroying coastal habitats. Roads, bridges, subways, water supplies, oil and gas wells, power plants, sewage treatment plants, and landfills remain at risk if sea level rise goes unchecked. 

• Melting of sea ice: Since 1979 arctic sea ice has declined by 30%. Sea ice plays a major role in regulating the earth’s climate by reflecting sunlight into space and providing habitat for animal species. If all of the glaciers on Earth melted, sea levels would rise by approximately 70 feet, effectively flooding out every coastal city on the planet. 

• Changing precipitation patterns: Extreme weather events (e.g., hurricanes, floods, droughts) are becoming more common and more intense. Storm-affected areas will experience increased precipitation and flooding whereas areas located further from storm tracks will experience decreased precipitation and droughts.

• Ocean acidification: The ocean absorbs 30% of the CO₂ released into the atmosphere, which decreases the pH (increases the acidity) of the ocean. In the past 200 years, the pH of oceans has decreased by 0.1 pH units, which translates to a 30% increase in acidity. Aquatic life unable to adjust to this rapid acidification will die off. A prime example of this is coral bleaching, where coral expel the algae (zooxanthellae) living in their tissues as a result of changes in temperature, light, or nutrients. 

Climate change results in global warming, when CO₂ and other air pollutants absorb sunlight and solar radiation in the atmosphere, thereby trapping the heat and acting as an insulator for the planet. Since the Industrial Revolution, Earth’s temperature has risen a little more than 1 degree Celsius (C), or 2 degrees Fahrenheit (F). Between 1880-1980 the global temperature rose by 0.07C every 10 years. This rate has more than doubled since 1981, with a current global annual temperature rise of 0.18C, or 0.32F, for every 10 years. 

Experts claim that to avoid a future plagued by rising sea levels, acidified oceans, loss of biodiversity, more frequent and severe weather events, and other environmental disasters brought on by the hotter temperatures, we must limit global warming to 1.5C by 2040. 

The international energy agency (IEA) estimates that in order for us to be net-zero by 2050, global H₂ supply (from water) must reach at least 80 million tons by 2030. Current supply is less than 50,000 tons, so more research and development will be required. 

The more we reduce CO₂ emissions, the more we slow the rate of temperature rise, sea-level rise, ice melting, and ocean acidification. When these rates are slowed, the earth’s biodiversity does not have to struggle to adapt to temperature and pH changes. People will not be displaced due to the flooding of coastal areas. And icebergs will continue to provide climate regulation. 

How Environmentally Friendly Is Hydrogen Fuel

H₂ fuel comes with lower levels of GHG emissions compared to petroleum-based fuels. 

“Environmentally friendly: (of products) not harming the environment.”

Cambridge Dictionary

Both the environmental benefits and drawbacks of H₂ fuel must be taken into consideration when discussing the issue of climate change.

What Are Environmental Benefits of Hydrogen Fuel

There are many environmental benefits of H₂ fuel, including:

• Climate change mitigation: Even when producing H₂ from NG and accounting for the delivery and storage of H₂ for use in FCEVs, H₂ can still cut GHG emissions by 50% and reduce petroleum consumption by 90%. This reduction in GHG emissions, in turn, reduces the effects of global climate change including increasing temperatures, rising sea levels, melting of sea ice, changing precipitation patterns, and ocean acidification.

• Few waste products: Water and warm air are the only waste products associated with the chemical reaction inside a fuel cell. 

• Versatility: H₂ can be sourced from renewable energy, coal, oil, NG, and nuclear power. It can be transported by pipeline, ship, or plane and can be used as electricity or transportation fuel.

• Energy independence: Being able to produce our own electricity in the US without the aid of foreign countries is an important step to help us become more self-sufficient. Former President George W. Bush signed the Energy Independence and Security Act of 2007 to reduce US dependence on oil, expand the production of renewable fuels (and confront global climate change). 

What Are Environmental Drawbacks of Hydrogen Fuel

H₂ fuel still comes with emissions, albeit not directly. Sourcing H₂ from NG produces approximately 830 million tons of CO₂ every year, which is equivalent to the emissions of the United Kingdom and Indonesia combined. NG is currently the top provider of H₂, and 7.5 billion tons of CO₂ every year occur because of NG combustion. Although the CO₂ emissions from the combustion of NG are about 50%-60% less than those from coal and oil, the primary component of NG is CH₄, a gas 34 times stronger at trapping heat than CO₂ over 100 years. This means that a little CH₄ can go a long way when contributing to global warming.

A way to avoid this environmental drawback is to acquire H₂ from low-carbon sources including solar power and wind power. These emit between 38-48 (solar) and 11-12 (wind) grams of CO₂ equivalent per kWh of electricity produced, compared to 490 grams for NG. Another option is to acquire H₂ from landfills and sewage treatment facilities, so long as CH₄ leaks are properly controlled. 

What Are Other Environmental Drawbacks of Hydrogen Fuel

The other main drawback with H₂ is the cost of producing it. It either requires large amounts of electricity if producing it from water, or the use of carbon capture technologies if producing it from fossil fuels. Most of the H₂ today comes from fossil fuel production without the use of carbon capture technology, resulting in nearly 900 million tons of CO₂ emissions. This is equal to the combined CO₂ emissions of the United Kingdom and Indonesia.

Capital investments and targeted policies will be necessary to close the price gap. For example, it can be anywhere from 2 to 7 times more expensive to produce H₂ from renewables (i.e., hydro-, wind-, solar energy) than it is to produce H₂ from natural gas (NG).

So far, the countries investing in H₂ have committed $37 billion (B) to research and development. For example, Germany has set a target of 5GW domestic capacity by 2030 and will spend 9 billion Euros (€9bn) on clean H₂ production and exporting technology. 

But although the private sector has invested another $300B, this is still below the estimated $1200B needed by 2030 in order to stay on the path to net-zero by 2050. 

Final Thoughts

H₂ fuel has a low carbon footprint across its building, extracting, transportation, and building back stages because it is clean-burning and does not produce any emissions upon operation.

Sourcing H₂ from renewable energy leads to a lower carbon footprint than if H₂ is sourced from fossil fuels. Right now, sourcing H₂ from NG is simply a stepping stone to a future powered by H₂.

Although H₂ fuel is versatile and can combat climate change, improve air quality, and promote energy independence, it has not gained traction in the commercial market because of high costs. In order to make H₂ fuel a greater part of our energy mix, more research and development of technology is needed.

Stay impactful,

Sources

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