Researchers at the University of Johannesburg have developed a new process to produce green hydrogen from sugarcane waste. This method is more efficient and cleaner than traditional biomass gasification. Their study appears in the journal Renewable Energy.
Every year, about 1.4 billion metric tons of sugarcane are produced globally. From this, around 540 million tons of bagasse, the leftover biomass, are generated. Countries like India, China, Brazil, and Mauritius already use bagasse to generate electricity for their grids.
Gasification turns biomass into syngas (a clean mix of hydrogen and other gases) without fire. But current methods produce a lot of tar, a sticky, dirty substance similar to engine oil, which increases costs for cleaning and maintenance.
Professor Bilainu Oboirien explained that typical biomass gasification results in low hydrogen yields and high tar production. It also releases significant amounts of carbon dioxide, which isn’t captured. This makes the process less efficient and more polluting.
A better approach is Sorption-Enhanced Chemical Looping Gasification (SECLG). Developed over the past decade, this method produces higher purity hydrogen, uses less energy, and captures carbon within the process. It also generates minimal tar.
The research team created a detailed computer model of SECLG, focusing on two types of metal oxides—nickel oxide and ferric oxide—as oxygen carriers. Their simulation showed that SECLG could produce hydrogen with 62-69% purity, with tar levels below 1 gram per cubic meter: a significant improvement.
This high-quality hydrogen could be used in various industries after further purification. Countries with existing biomass plants, like Brazil, China, and South Africa, could adapt current infrastructure to implement SECLG more easily and cheaply.
The study also compared the effectiveness of different oxygen carriers. Nickel oxide produced purer hydrogen and captured carbon dioxide better, while ferric oxide could be tuned to produce fuels like diesel.
However, challenges remain. The models do not yet account for how materials degrade over time or how to efficiently remove ash and char. The researchers are now conducting laboratory experiments to validate their models.
Scaling up SECLG requires high temperatures and pressure, and continuous operation cycles. Despite these hurdles, Prof. Oboirien believes that with investment and collaboration, this technology could revolutionize green hydrogen production and help decarbonize energy-intensive industries.