Hydrogen's Impact: Air Pollution Or Clean Energy?

Hydrogen is a possible energy carrier for future energy systems, with the ability to be produced from many primary energy sources and more easily stored than electricity. However, the impact of large-scale hydrogen use on the atmosphere is uncertain. Hydrogen combustion does not produce carbon dioxide (CO2) emissions, but it can produce dangerously high levels of nitrogen oxide (NOx), a hazardous air pollutant. Hydrogen is currently produced through a dirty process that relies on fossil fuels and emits a significant amount of carbon pollution. However, there is potential to produce a green version of hydrogen using renewable energy and water, which could help reduce air pollution.

Hydrogen combustion produces high levels of nitrogen oxide (NOx)

Nitrogen oxides (NOx) are hazardous air pollutants that are produced during high-temperature combustion. This includes the combustion of diesel, gasoline, natural gas, and hydrogen. Hydrogen burns at a higher temperature than natural gas, which means that hydrogen combustion may result in higher NOx emissions. However, hydrogen has a larger stable combustion temperature range, which means that a higher ratio of air to fuel can be used. This additional air dilutes the hydrogen, cooling the flame and resulting in lower-temperature combustion. This, in turn, reduces the amount of NOx emitted.

Research has shown that hydrogen combustion via turbines can achieve comparable NOx emissions to those of today's turbines running on natural gas. However, some have argued that hydrogen combustion can produce dangerously high levels of NOx. This is a particular concern for aircraft propulsion, as the combustion of hydrogen in this context could increase pollution in the form of oxides of nitrogen. This would partially negate the environmental benefits of burning hydrogen.

There are multiple mitigation strategies to prevent or reduce NOx emissions when hydrogen is used for combustion. For example, flue gas treatment approaches can convert harmful emissions into less harmful compounds, using processes similar to those in catalytic converters.

The overall impact of a hydrogen-based energy system on atmospheric chemistry is uncertain. Hydrogen use in clean fuel cells reduces emissions of air pollutants such as nitrogen oxides, but emissions from hydrogen production and leakages of molecular hydrogen could influence atmospheric chemistry. Some studies have claimed that large-scale emissions of molecular hydrogen from system leakages could lead to enhanced climate change or influence the chemical composition of the atmosphere.

Hydrogen can be used in clean fuel cells to reduce air pollutants

Hydrogen is a promising energy carrier for future energy systems. It can be produced from many primary energy sources, can be more easily stored than electricity, and allows for very low emissions of air pollutants during the end-use stage.

One of the most significant advantages of using hydrogen is that it can be employed in clean fuel cells, which can significantly reduce air pollutants. Fuel cells generate electricity through an electrochemical reaction instead of combustion, even at high temperatures of up to 1,000°C, resulting in zero harmful direct emissions. This makes them a zero-emissions alternative to fossil fuels and internal combustion engines in heavy-duty vehicles, trains, and ships. By transitioning from traditional combustion engines, which release harmful emissions, to hydrogen fuel cells, we can improve local air quality.

However, it is important to acknowledge that hydrogen combustion, particularly in turbines used for electricity generation or industrial heating applications, can produce high levels of nitrogen oxides (NOx), which are hazardous air pollutants. NOx formation occurs when air, containing nitrogen and oxygen, is exposed to very high temperatures (>1,500°C). Hydrogen, burning at higher temperatures than natural gas, can result in higher NOx emissions. Nevertheless, hydrogen's larger stable combustion temperature range allows for a higher ratio of air to fuel, diluting the hydrogen and leading to lower-temperature combustion, thus reducing NOx emissions.

While the overall impact of a hydrogen-based energy system on atmospheric chemistry remains uncertain, studies have shown that hydrogen energy use can lead to a decrease in emissions of carbon monoxide, nitrogen oxides, and sulphur dioxide. However, large-scale hydrogen production, especially from coal, may increase emissions of nitrous oxide and volatile organic compounds. Additionally, system leakages of molecular hydrogen could influence atmospheric chemistry and potentially enhance climate change.

Despite this, hydrogen fuel cell technology shows promising signs of cleaning the air. Automotive manufacturers are increasingly focusing on hydrogen fuel cells as a cleaner solution, and state governments are pushing for greener initiatives. For instance, California plans to phase out new gas-powered vehicles by 2035, creating an opportunity for the adoption of air-purifying car tech. Hyundai, for example, claims that its Nexo system can filter out 99.9% of harmful gases and microscopic particles.

Hydrogen is a possible energy carrier for future energy systems

Hydrogen is the most abundant element on Earth, consisting of only one proton and one electron. It is an energy carrier, not an energy source, and can store and deliver usable energy. Hydrogen can be produced from diverse, domestic resources, including fossil fuels, specifically natural gas, and electricity from the grid or renewable sources such as biomass, geothermal, solar, or wind.

Despite these concerns, hydrogen has several advantages as a possible energy carrier. Hydrogen-based energy systems can be centralized and based on renewables and/or fossil energy combined with carbon capture and storage. Hydrogen can also be more easily stored than electricity, and it has a high energy density, providing a robust alternative to fossil fuels. Hydrogen and fuel cells have the potential to significantly reduce emissions across various sectors, including transportation, commercial, industrial, and residential.

To realize the potential of hydrogen as an energy carrier, technological and infrastructural challenges must be addressed. The inefficiency of current electrolysis methods and high production costs are significant obstacles to the expansion of hydrogen technology. Advancements in electrolysis efficiencies and cost reductions are necessary to make hydrogen a more viable option. Additionally, regulatory frameworks and strategic planning are crucial to enhancing the economic viability and market integration of hydrogen.

Hydrogen safety research is critical for its use in the economy

Hydrogen is an attractive energy carrier that can be produced by renewable sources and utilized as an alternative to hydrocarbons. It is known as a possible energy carrier for future energy systems. However, the impact of large-scale hydrogen use on the atmosphere is uncertain. While hydrogen use in clean fuel cells reduces emissions of air pollutants, emissions from hydrogen production and leakages of molecular hydrogen could influence atmospheric chemistry.

The overall impact of a hydrogen-based energy system on atmospheric chemistry is uncertain. On the one hand, the use of hydrogen in clean fuel cells eliminates the end-use phase emission of air pollutants, such as sulphur dioxide (SO2) and nitrogen oxides (NOx). On the other hand, air pollutant emissions could still occur during hydrogen production. Some studies have claimed that large-scale emissions of molecular hydrogen from system leakages could also lead to enhanced climate change or influence the chemical composition of the atmosphere.

Safety is a critical factor in the widespread adoption of hydrogen as an energy source. Hydrogen is known as the least dense gas in the world, and this causes challenges in terms of storage and transport. High-pressure compression is a commonly used storage method due to its economy, but it is not ideal for hydrogen due to the low gravimetric storage density in heavy steel vessels. The incompatibility between hydrogen and steel materials can also cause hydrogen embrittlement in vessel storage.

The development of cutting-edge technologies for hydrogen safety is essential to address these challenges. Reliable sensors for hydrogen leak detection are crucial, as well as the development of comprehensive safety standards through further research on hydrogen safety fundamentals. The effective application of hydrogen energy depends on ensuring its safety during production, transmission, and use. Hydrogen safety research is vital to address these challenges and enable the widespread adoption of hydrogen in the economy.

Hydrogen is a clean substitute for fossil fuels

Hydrogen is a versatile energy carrier that can be used to tackle various critical energy challenges. It is mostly used in the refining and chemical sectors, including fertilizer production and oil refining. However, supporters of hydrogen fuel envision its use in transportation fuel, home heating and cooking, and augmenting wind and solar generation.

Hydrogen is currently produced from fossil fuels, which results in significant CO2 emissions. However, low-emissions hydrogen produced with renewable or nuclear energy, or fossil fuels using carbon capture, can help to decarbonize hard-to-abate sectors, such as heavy industry and long-distance transport. Hydrogen can also support the integration of variable renewables in the electricity system, as it is one of the few options for storing energy over extended periods.

The use of hydrogen in clean fuel cells reduces emissions of air pollutants such as sulphur dioxide (SO2) and nitrogen oxides (NOx). However, hydrogen combustion can produce high levels of NOx, which are hazardous air pollutants. The production and leakage of molecular hydrogen could also influence atmospheric chemistry and potentially enhance climate change. The overall impact of a hydrogen-based energy system on atmospheric chemistry is uncertain, and more research is needed to understand the effects of large-scale hydrogen use.

Despite these uncertainties, hydrogen is an attractive alternative to fossil fuels due to its low emissions during the end-use stage and the ability to produce it using renewable energy sources. Global hydrogen demand is increasing, and many governments have adopted hydrogen strategies. With the right measures in place to prevent leaks and emissions, hydrogen could be a clean substitute for fossil fuels, helping to reduce the warming impacts of greenhouse gases.

Frequently asked questions