Grey and blue hydrogen: Insights into production technologies and outlook on CO2-free alternatives

Abstract

Hydrogen is anticipated to accelerate the mitigation of climatic challenges in the upcoming future. Globally, for every kg of H₂ produced, around 11–12 kg of CO₂ is emitted. While adding CCS to existing systems increase the cost and complexity and leads to both CO₂e and fugitive emissions. It is important to develop low-carbon approaches for the existing technologies to address the environmental concerns and to meet the global energy goals on decarbonization. This paper presents various existing hydrogen production methods using hydrocarbon feedstock concerning operating principles, technical barriers, advancements and prevailing challenges and economic and environmental aspects. Additionally, the paper highlights the present status of the real-time blue hydrogen plants globally. It discusses the CO₂-free alternative methods such as solar-SMR and methane pyrolysis covering their status quo in becoming the sustainable energy choice. It also identifies and addresses the key difficulties in the production of low-carbon H₂. Carbon-pricing is trying to hasten the adoption of green energy and carbon abatement by increasing the cost of hydrogen production. However, detailed investigations in the techno-economic aspects incorporating the ecological benefits are required for developing H₂ as an alternative fuel for sustainable development.