Hydrogen power and climate change
Hydrogen power represents a potential alternative energy source that could significantly influence climate change mitigation efforts. Molecular hydrogen (H₂) is recognized for its high energy content, being three times more efficient than gasoline. While hydrogen is abundant in the universe, it is rarely found in its pure form on Earth, necessitating processes such as electrolysis or steam reforming of natural gas to produce it. The challenge lies in generating hydrogen sustainably without contributing to greenhouse gas emissions, which are a major factor in climate change. Current hydrogen production methods often result in carbon dioxide emissions, but advances in technology may allow for cleaner production techniques, such as using renewable energy sources like wind and solar power.
One promising avenue for hydrogen generation is biohydrogen, produced by microorganisms through photosynthesis, which harnesses sunlight and water. Fuel cells, an alternative to internal combustion engines, can utilize hydrogen to generate electricity, emitting only water as a by-product, thus offering a cleaner solution for transportation. However, hydrogen vehicles are currently outpaced by electric vehicles in terms of market adoption. For hydrogen power to thrive, significant investments in research, infrastructure, and consumer acceptance will be essential. As the world seeks sustainable energy solutions, hydrogen power may play a pivotal role in reducing reliance on fossil fuels and addressing climate change.
Subject Terms
Hydrogen power and climate change
Definition
Molecular hydrogen (H2) is an ideal fuel to be used for transportation, since the energy content of hydrogen is three times greater than that of gasoline and four times greater than that of ethanol. Hydrogen powered rockets have been launched by the National Aeronautics and Space Administration (NASA) for many years. Today, a growing number of automobile manufacturers around the world are making hydrogen-powered vehicles. Because of depleting supplies and growing demand for oil, H2 may become an alternative to gasoline.
The idea of hydrogen as the fuel of the future was expressed long ago by Jules Verne in his novel L’Île mystérieuse (1874–75; The Mysterious Island, 1875). However, compared to oil, H2 is not abundant on Earth. Its atmospheric concentration is only 0.00001 percent, and there is even less of it in the oceans. Though many microorganisms produce H2 during fermentation, it is such a good source of energy that it is used almost immediately by other microbes. Thus, in order for humans to use hydrogen as fuel, it must be generated using other energy sources.
While molecular hydrogen is rare, the chemical element hydrogen is the most basic and plentiful element in the universe. It also forms a part of the most abundant chemical compound on Earth, water. Therefore, the challenge posed is to find a cost-effective and environmentally friendly way to generate H2 from water or other chemical compounds. At present, H2 is obtained mainly from natural gas (methane and propane) via steam reforming. Although this approach is practically attractive, it is not sustainable. Molecular hydrogen can also be produced by electrolysis. In this process, electric energy is employed to split water into H2 and O2. The requisite electricity can be obtained using clean, sustainable energy technologies such as wind and solar power. However, the process is not efficient, requiring significant expenditure of energy and purified water.
There are other technological and economic obstacles to hydrogen power. These obstacles include safety issues, as well as the lack of effective solutions for storage and distribution of H2. Hydrogen has gained an unwarranted reputation as a highly dangerous substance among the public. Like all fuels, H2 may produce an explosion, but it has been used for years in industry and earned an excellent safety record when handled properly.
Hydrogen is the lightest chemical, so it has a much lower energy density by volume than do other fuels. As a gas, it requires three thousand times more space for storage than does gasoline. Thus, hydrogen storage, especially in cars, represents a challenge for scientists and engineers. For storage, H2 is pressurized in cylinders or liquefied in cryotanks at –253° Celsius. Both processes require a significant expenditure of energy and generate large quantities of waste carbon dioxide (CO2). In most contemporary hydrogen-powered vehicles, H2 is stored as compressed gas. Because compressed gas cannot be delivered in the same fashion as liquid fuel, gasoline stations and pumps cannot simply be converted into hydrogen stations. Thus, the distribution system for the new fuel would have to be constructed from scratch, requiring considerable monetary investment.
Significance for Climate Change
Fossil fuels generate CO2, contributing to the greenhouse effect. Switching from fossil fuels to H2 would eliminate that source of greenhouse gas (GHG) emissions, provided that the new fuel could be produced without carbon-emitting technologies. Burning H2 for an energy source produces only water as a by-product, and H2 is also a renewable fuel, since it can be made from water again. Unfortunately, current methods of H2 production from natural gas also generate CO2. The ultimate goal is to generate H2 without emitting GHGs into the atmosphere, perhaps by using wind or solar power.
One promising green method of H2 production is a biological approach: A great number of microorganisms produce H2 from inorganic materials, such as water, or from organic materials, such as sugar, in reactions catalyzed by the enzymes hydrogenase and nitrogenase. Hydrogen produced by microorganisms is called biohydrogen. The most attractive biohydrogen for industrial applications is that produced by photosynthetic microbes. These microorganisms, such as microscopic algae, cyanobacteria, and photosynthetic bacteria, use sunlight as an energy source and water to generate hydrogen. Hydrogen production by photosynthetic microbes holds the promise of generating a renewable hydrogen fuel using the plentiful resources of solar light and water.
It is possible to use hydrogen to fuel internal combustion engines. Doing so produces at least one GHG, nitrogen oxide, because the burning of hydrogen requires air, which is almost 80 percent nitrogen (N2). To use hydrogen power in climate-friendly ways, it will be necessary to replace the internal combustion engine with fuel cells, which produces electricity to power vehicles without motors. Fuel cells are like batteries: They generate electricity via chemical reactions between H2 and O2. Fuel cells emit water and heat, not CO2 or other GHGs. In addition, fuel cells are 2.5 to 3 times more efficient in converting H2 energy than are internal combustion engines. Hydrogen fuel-cell cars could even provide power for homes and offices if necessary. Three car companies have entered hydrogen-powered cars into the marketplace since 2015: Honda introduced their Clarity Fuel Cell, Hyundai offered their Nexo SUV, and Toyota brought the Mirai. However, the Clarity was discontinued, and the Nexo experienced disappointing sales. Toyota was committed to marketing a hydrogen-powered car, though only 2,737 Mirai sedans had been sold in the United States as of 2023, according to Car and Driver. Electric vehicles (EVs) remained a more viable option for zero-emission vehicles, with 1.2 million EVs sold in the United States as of 2023 compared to 2,968 hydrogen-powered vehicles.
For hydrogen power to become a reality, tremendous research and investment efforts are necessary. The fate of hydrogen power technology will also depend on consumers’ willingness to spend money on climate-friendly technologies.
Bibliography
Conrad, Cross, Karson Taylor, and Mikaela Wells. "Is Hydrogen Energy Key to Solving the Climate Crisis?" The Regulatory Review, 8 June 2024, www.theregreview.org/2024/06/08/is-hydrogen-energy-key-to-solving-the-climate-crisis/. Accessed 10 Dec. 2024.
Miller, Caleb. "2024 Toyota Mirai FCEV Receives Updates, Including a New Badge." Car and Driver, 25 Jan. 2024, www.caranddriver.com/news/a46541268/2024-toyota-mirai-hydrogen-updates/. Accessed 12 Dec. 2024.
Ogden, Joan. “High Hopes for Hydrogen.” Scientific American Sept. 2006: 94–99. Print.
Service, Robert F. “The Hydrogen Backlash.” Science 305.5686 (2004): 958–61. Print.
Voelcker, John. "Hydrogen Cars: Everything You Need to Know." Car and Driver, 29 Apr. 2023, www.caranddriver.com/features/a41103863/hydrogen-cars-fcev/. Accessed 12 Dec. 2024.
Zaborsky, Oskar R., ed. Biohydrogen. New York: Plenum, 1998. Print.