Effects of hydrogen blending on methane emissions in natural gas distribution and end-use piping

Abstract Hydrogen is seen as a promising energy carrier, as society seeks to achieve net-zero emissions. One approach to integrating hydrogen into energy systems is to blend it with natural gas, which could decrease the quantity of methane, the primary component of natural gas and a potent greenhouse gas, emitted to the atmosphere. Due to hydrogen’s small molecular size and high mobility, there is concern that hydrogen-natural gas blends (hythane) may leak more than pure natural gas. Previous studies indicate that blends up to ∼20% hydrogen by volume may be used in existing natural gas infrastructure, but additional studies are needed for higher hydrogen contents. Therefore, we conducted chamber-based methane emission measurements at natural gas distribution infrastructure and end-use piping using hythane of 0%–40% hydrogen by volume. We found that total methane emissions were 7%–26% lower for hythane than for natural gas only; however, methane gas loss rates were between 3.5% and 6.5% higher for hythane blends than for natural gas, with higher gas loss rates for increasing hydrogen content. Average in-pipe flow rates increased proportionally with hydrogen content when the pressure of the pipeline was between 1.6 kPa and 16 kPa; however, we did not observe this trend for the higher-pressure pipeline measured (385 kPa). Further, we saw gas loss rates were mildly correlated to average in-pipe flow rates but were not correlated to in-pipe flow regime. Our testing shows that total methane leakage can be reduced by hythane blending for up to 40% hydrogen content, with minimal infrastructure upgrades in the short term. However, testing across a wider range of infrastructure and long-term studies are needed to fully evaluate methane leakage during hythane usage in existing infrastructure.