title: Comparison between Green and Blue Hydrogen Production: Climate Impact, Status Quo and Prospects
Creators: name: Barbosa Aguas, Oscar Ivan
Publisher: name: TU Wien
Year: 2023
Subjects: subject: Low-emission hydrogen
subject: Carbon intensity
subject: Carbon capture
subject: Electrolysis
subject: Hydrogen demand

description: Blue and green hydrogen are considered low-carbon technologies and important players in decarbonizing the energy sector and tackling CO2-eq emissions. However, hydrogen production is currently dominated by fossil fuels (gas, oil, and coal), which are known as gray, black, or brown hydrogen. Gray hydrogen is converted to blue when it is coupled with CCUS to capture and store CO2 emissions. On the other hand, green hydrogen comes from electrolysis using renewable electricity from wind and solar PV, among others. A literature review of gray, blue, and green hydrogen production technologies is carried out. The results of the literature review show that blue hydrogen production does not capture all CO2 emissions, capture efficiencies vary depending on the selected technology, and methane leakage rates during production and transport are significant. Green hydrogen has the lowest climate impact because there is no direct use of fossil fuels. However, its deployment is still in development. In this thesis, a comparative analysis of the climate impact of the estimated hydrogen demand for 2030 and 2050 was conducted according to the future shares of gray, blue, and green hydrogen using calculated carbon intensities (CO2-eq/kgH2). Results show that i) there is a significant reduction of emissions when the share of gray hydrogen is overcome by blue and green hydrogen in every scenario; ii) comparing the results with previously estimated emissions for 2020 and 2030, it can be seen that previous CO2-eq emissions were underestimated; iii) only for the 100% green hydrogen scenario, emissions were close to or under the CO2-eq emissions of 2020. It is important to note that the data used for the comparative analysis are estimates and do not correspond to what is currently achieved in terms of efficiency, carbon capture rate, and methane leakage. In conclusion, under current technological conditions, green hydrogen is the least carbon-intensive option compared to blue and gray hydrogen, and its share in the hydrogen mix should be prioritized. However, the carbon intensity of green hydrogen depends on the adopted renewable energy source.
description: Blue and green hydrogen are considered low-carbon technologies and important players in decarbonizing the energy sector and tackling CO2-eq emissions. However, hydrogen production is currently dominated by fossil fuels (gas, oil, and coal), which are known as gray, black, or brown hydrogen. Gray hydrogen is converted to blue when it is coupled with CCUS to capture and store CO2 emissions. On the other hand, green hydrogen comes from electrolysis using renewable electricity from wind and solar PV, among others. A literature review of gray, blue, and green hydrogen production technologies is carried out. The results of the literature review show that blue hydrogen production does not capture all CO2 emissions, capture efficiencies vary depending on the selected technology, and methane leakage rates during production and transport are significant. Green hydrogen has the lowest climate impact because there is no direct use of fossil fuels. However, its deployment is still in development. In this thesis, a comparative analysis of the climate impact of the estimated hydrogen demand for 2030 and 2050 was conducted according to the future shares of gray, blue, and green hydrogen using calculated carbon intensities (CO2-eq/kgH2). Results show that i) there is a significant reduction of emissions when the share of gray hydrogen is overcome by blue and green hydrogen in every scenario; ii) comparing the results with previously estimated emissions for 2020 and 2030, it can be seen that previous CO2-eq emissions were underestimated; iii) only for the 100% green hydrogen scenario, emissions were close to or under the CO2-eq emissions of 2020. It is important to note that the data used for the comparative analysis are estimates and do not correspond to what is currently achieved in terms of efficiency, carbon capture rate, and methane leakage. In conclusion, under current technological conditions, green hydrogen is the least carbon-intensive option compared to blue and gray hydrogen, and its share in the hydrogen mix should be prioritized. However, the carbon intensity of green hydrogen depends on the adopted renewable energy source.