5. Hydrogen Production Technologies: Pathways to a Sustainable and Cleaner Environment

Over the years, rising energy demand in various sectors, including transportation, is majorly fulfilled by fossil fuels, leading to global warming. To reduce greenhouse gases from the transportation sector, hydrogen offers huge potential for decarbonizing as it is a flexible and clean energy source. However, not all hydrogen is made equally. The process used to manufacture hydrogen significantly impacts the environment, ranging from significant greenhouse emissions to almost zero emissions. Hence, it is necessary to promote cleaner hydrogen production for a sustainable energy future and a cleaner environment. Hydrogen can be produced using various methods, but some of the most commonly used methods are steam methane reforming, coal gasification, biomass gasification, and electrolysis using electricity or renewable energy sources. Depending on the hydrogen production pathway and the option of CO₂ sequestration, hydrogen can be classified as black/brown, gray, blue, green, pink, purple, turquoise hydrogen, etc. The most conventional hydrogen production methods, like SMR, emit about 9–12 kg of CO₂, and coal gasification produces about 18–20 kg of CO₂ per kg of H₂, proving that they are neither green nor environmentally sustainable. However, the electrolysis processes using electricity generated using renewable energy are the ones that are greener and benefit a cleaner environment. Moreover, hydrogen can also be produced through biochemical pathways. Fermentation of hydrolysates produced from different lignocellulosic biomass can yield biohydrogen. This is also a clear route of hydrogen production from renewable sources. So, this chapter critically discusses the various hydrogen production technologies, their greenhouse gas emissions, the cost of production, and large-scale production feasibility to make a suitable choice of hydrogen production technology for a cleaner environment.