HOW IS HYDROGEN PRODUCED?
Hydrogen can be produced from diverse domestic resources, including fossil fuels, biomass, and water electrolysis with electricity. The environmental impact and energy efficiency of hydrogen depends on the production process. There are current projects aimed at decreasing the costs of hydrogen production.
Evolving Hydrogen Production Technologies:
- Natural Gas Reforming/Gasification: This method is currently the cheapest, most efficient, and most common form of hydrogen production in the U.S - synthesis gas, a mixture of hydrogen, carbon monoxide, and a small amount of carbon dioxide, is created by reacting natural gas with high-temperature steam. The carbon monoxide is reacted with water to produce additional hydrogen. In a process called gasification, a synthesis gas can be created by reacting coal or biomass with high-temperature steam and oxygen in a pressurized gasifier, which is converted into gaseous components. The resulting synthesis gas contains hydrogen and carbon monoxide, which is reacted with steam to separate the hydrogen.
- Electrolysis: In electrolysis, electricity is used to split water into hydrogen and oxygen - this reaction takes place in a unit called an electrolyzer. Hydrogen production where wind or nuclear energy are the electricity source results in virtually zero greenhouse gas and criteria pollutant emissions. Wind-based electricity production is growing rapidly in the U.S. and globally. On wind farms, hydrogen production can solve the issue of wind variability, since in times of excess wind, instead of curtailing the electricity production, it is possible to use the excess electricity to produce hydrogen.
- Renewable Liquid Reforming: In a process similar to natural gas reforming, liquid fuels derived from biomass resources are reacted with high-temperature steam to produce hydrogen. Biomass-derived liquid fuels are easier to transport than their biomass feedstocks - presenting potential opportunities for hydrogen production at fueling stations. In the U.S. there is more biomass available than is required for food and animal feed needs, and, since plants consume carbon dioxide from the atmosphere as they grow, that off-sets the carbon dioxide released from producing hydrogen through biomass gasification - resulting in low net greenhouse gas emissions.
- Fermentation: In fermentation-based systems, microorganisms - such as bacteria - break down organic matter – such as refined sugars, or raw biomass sources, or wastewater - to produce hydrogen. Fermentation-based systems have the potential to produce hydrogen from resources that otherwise can’t be used for fuel production, and fermentation can reduce the large amount of energy normally needed for wastewater treatment, while producing hydrogen for fuel.
- High-Temperature Water Splitting: High temperatures, produced by solar concentrators or nuclear reactors, drive chemical reactions that split water to produce hydrogen, with near-zero greenhouse gas emissions.
- Photobiological Water Splitting: Microbes, such as green algae, consume water in the presence of sunlight and produce hydrogen as a byproduct.
- Photoelectrochemical Water Splitting: Using special semiconductors and energy from sunlight, photoelectrochemical systems produce hydrogen from water.
Updated June 2022 by Erin Bennett
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