To meet state and local climate goals, gas utilities across the United States are looking towards alternative fuel sources such as hydrogen and biogas—also referred to as renewable natural gas (RNG)—to decarbonize their future gas supply. Along with maximizing energy efficiency and making further investments in gas infrastructure, recent planning documents from gas utilities like National Grid and Washington Gas highlight a shift towards low and zero-carbon fuels such as RNG and hydrogen.
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Hydrogen is not an energy source itself; it is an energy carrier. There are several types, or “colors”, of hydrogen that are distinguished by the energy source and process used to produce it. “Green” hydrogen—which is produced through electrolysis of water using electricity from renewable sources such as wind or solar—releases zero greenhouse gas emissions when burned for energy. Green hydrogen itself is not a zero-emission fuel source: If leaked directly into the atmosphere green hydrogen is an indirect greenhouse gas and its combustion has been found to emit nitrogen oxides (NOx), which is a criteria air pollutant. Since it can be mixed with fossil-sourced gas, green hydrogen is attractive to gas utilities who want to continue to use their existing gas pipelines while attempting to comply with climate mandates.
Several economic, technical, and infrastructure barriers stand in the way of using green hydrogen in decarbonization:
Green hydrogen is more expensive than its dirtier counterparts (e.g., hydrogen made using fossil fuels), fossil fuels themselves, and grid electricity.
Hydrogen production is inefficient. The International Renewable Energy Agency estimates that 30 to 35 percent of its energy is lost during electrolysis.
Hydrogen poses a risk to public safety. Hydrogen molecules are more likely to leak through pipeline imperfections and escape existing gas pipelines; hydrogen can also degrade the materials used for pipelines.
Due to insufficient infrastructure, and regardless of demand, hydrogen could only be injected into existing gas pipelines to make up 5 to 15 percent of total gas volume.
Even if these barriers could be overcome, an important question remains: Is the production of green hydrogen the best use of renewable resources?
Electrification, or the replacement of fossil-fuel dependent technologies (like gas and oil heating systems or gasoline-powered motor vehicles) with those that rely on electricity, is an alternative decarbonization method gaining traction across the United States. When sourced from renewables, heating our homes with electricity rather than gas or gas mixed with hydrogen, can significantly reduce emissions without the safety concerns of piped gas and costly infrastructure upgrades needed to make hydrogen work.
As the United States works towards electrifying sectors throughout the economy, the demand for electricity, and subsequently the demand for renewables, will rise. The use of green hydrogen as energy storage in time periods when the supply of renewables exceeds electric demand may be a viable option worth comparing to other storage technologies, but maintaining and improving costly gas delivery infrastructure is far less likely to make sense economically or socially.
