Hydrogen is a versatile and clean energy carrier that has the potential to play a significant role in our transition to a sustainable and low-carbon economy. There are various methods of hydrogen production, and they can be grouped into two categories based on the source of production: Renewable sources and Fossil fuels.
Renewable- based Hydrogen Production
The production of green hydrogen can be achieved through various methods, as indicated above. However, for the purpose of this essay, we will focus on two primary approaches – electrolysis and biomass-based processes
Water Splitting (Electrolysis)
Electrolysis is a promising method of green hydrogen production that has been widely studied and tested. The process involves the use of an electric current to split water molecules into hydrogen and oxygen. The electrolysis process can be powered by renewable energy sources such as wind, solar, or hydroelectric power, which makes it a sustainable method of hydrogen production with no greenhouse gas emissions. Additionally, the efficiency of the electrolysis process is continuously improving with the development of more advanced technologies and materials.
There are several types of electrolysis, including alkaline, polymer electrolyte membrane (PEM), and solid oxide electrolysis. Alkaline electrolysis is the most mature and widely used method, with large-scale systems already in operation. PEM electrolysis has the advantage of higher efficiency and flexibility in operation, but it is still in the early stages of commercialization. Solid oxide electrolysis has the potential for high efficiency and high-temperature operation, but it is still in the research and development stage.
Biomass Process
Biomass-based hydrogen production involves the use of biomass as a feedstock to produce hydrogen through processes such as gasification and pyrolysis. In gasification, biomass is heated in the absence of oxygen to produce a gas that contains hydrogen, carbon monoxide, and other gases. The gas can then be purified to produce high-purity hydrogen. Pyrolysis involves the heating of biomass in the absence of air to produce a solid, liquid, or gas product, with the gas product containing hydrogen.
Biomass-based hydrogen production has the potential to be a sustainable method of hydrogen production as it can use a variety of biomass feedstocks, including agricultural waste and wood chips. Furthermore, this method has the added benefit of utilizing waste materials that would otherwise be discarded.
In recent years, there has been a growing interest in combining biomass-based hydrogen production with carbon capture and storage (CCS) technologies. CCS can capture the carbon dioxide emissions from biomass-based hydrogen production processes, preventing them from entering the atmosphere and mitigating the environmental impact of the process. However, the integration of CCS technologies with hydrogen production processes can increase the cost and complexity of the process.
Fossil fuel- based Hydrogen Production
Fossil fuel-based hydrogen production involves processes such as steam methane reforming (SMR) and pyrolysis.
SMR Process
SMR is a process used to produce hydrogen from natural gas. In this process, natural gas is mixed with steam and heated to high temperatures, causing a chemical reaction that produces hydrogen and carbon monoxide. The carbon monoxide can then be further reacted to produce additional hydrogen. SMR is a widely used method for producing hydrogen, but it is not considered a sustainable method as it produces carbon dioxide emissions.
Pyrolysis
Methane pyrolysis is a process that involves heating methane gas to produce hydrogen and solid carbon. It is carried out at high temperatures between 700°C and 1200°C, and the hydrogen gas produced can be used as a clean fuel for transportation and power generation. The solid carbon produced can also be used for industrial applications.
Methane pyrolysis has the potential to be a sustainable method for producing clean hydrogen if the methane used is obtained from renewable sources such as biogas or waste gas streams. However, the process still requires energy to heat the methane, and if that energy comes from fossil fuels, it can result in carbon emissions. Nevertheless, the development of low-cost and renewable energy sources could make methane pyrolysis an attractive option for producing clean hydrogen.
The information presented in this essay is based on the article “A comparative overview of hydrogen production processes” by Pavlos Nikolaidis and Andreas Poullikkas, published by Elsevier Ltd. in 2016.
