Can Hydrogen substitute Carbon and avoid catastrophic climate change

The answer is most likely NO for the following reasons.

It has been established that man-made GHG emissions mainly by CO2 is causing the globe to warm by a phenomenon known as “Greenhouse gas effect” triggering change in climate. Therefore, many are suggesting Hydrogen as an alternative clean fuel to reduce or eliminate CO2 emission. But replacing Carbon with Hydrogen we will only substitute Oxides of Carbon (CO2) with Oxides of Hydrogen (H2O). But water vapor too is a potent greenhouse gas GHG and it may enhance the warming of the globe by a phenomenon known as Feedback effect as explained by NASA and American chemical society (ACS) by the following references:

1. https://www.acs.org/content/acs/en/climatescience/climatesciencenarratives/its-water-vapor-not-the-co2.html
2. https://phys.org/news/2014-03-effect-vapor-climate.html
3.  http://theconversation.com/climate-explained-why-carbon-dioxide-has-such-outsized-influence-on-earths-climate-123064
4. https://www.nasa.gov › topics › earth › features › vapor_warming

Moreover, Renewable Hydrogen is still very expensive compared to Hydrogen derived from fossil fuel such as coal and gas even though cost of renewable energy has reduced substantially in recent past. By injecting valuable renewable Hydrogen into existing pipeline carrying natural gas one will generate additional issues because of varying physical and chemical properties of Hydrogen and its flammability and explosive nature compared to natural gas. Only a mixture of Hydrogen 30% and natural gas 70% has been tested using gas turbines. The combustor is a critical component of the turbine and still problems like flame back firing, Hydrogen embrittlement and suitable materials of construction for 100% Hydrogen are still a long way off. The heat of combustion of Hydrogen and natural gas using pure Oxygen can be shown as below;

2H2 (g) + 2 O2 (g) > 2H2O  – 286 kj/mole

CH4 (g) + 2 O2 (g) > CO2 + 2H2O – 889 kj/mole

Clearly the heat of oxy combustion of natural gas is high even though the heating value of Hydrogen is high compared to natural gas. Even with 100% Hydrogen, gas turbine will emit water vapour along with Oxides of Nitrogen which is still need to be addressed. I cannot imagine using pure Oxygen for Hydrogen combustion. Combustion of Hydrogen or combustion of  a mixture of hydrogen and Natural gas will emit water vapour or a mixture of water vapour, CO2 and oxides of Nitrogen and they will not help mitigate the climate change. Imagine thousands of cars running on Hydrogen emitting water vapour! It will certainly change the climate in the shortest period because the atmosphere will be saturated with water vapour increasing the ambient temperature. The feed back effect of water vapor will enhance the global warming in presence of CO2 as shown above.

Hydrogen is an unstable atom and readily forms a bond with Oxygen and Carbon and that is why Nature does not produce free Hydrogen. It requires a Carbon backbone. Only an emission free power generation technology can solve the problem of global warming. It is only possible by recycling Carbon (Carbon recycling technology) with the help of renewable Hydrogen and to achieve a circular economy. There is no shortcut.