Natural gas is 70-90% methane. Hydrogen can be combined with environmental sources of carbon dioxide (e.g., biogas effluents) to make methane. Doing so makes it entirely compatible with every use of natural gas. The main advantage of hydrogen as a fuel in place of fossil fuels is that its use releases no carbon dioxide.
Hydrogen itself has chemical and energetic properties that differ from methane/natural gas. Perhaps the most salient difference is that it has a lower heat content per volume (e.g. cubic foot) of natural gas. As a result, beyond 20-30% mixture of hydrogen and natural gas, natural gas appliances may function noticeably differently with hydrogen. With adjustments, most uses of natural gas can be met with hydrogen. Major gas turbine manufacturers have said their existing gas turbines can run on a combination of natural gas and up to 30% hydrogen (by volume) without modification. Gas turbines capable of running on 100% hydrogen are planned by manufacturers for the 2030-2035 timeframe.
Manufacturer hydrogen power plant links: