Producing hydrogen fuel from solar power and agricultural waste

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Researchers at the University of Illinois Chicago (UIC) have developed a new method to make hydrogen gas from water using solar power and agricultural waste like manure or husks. The researchers said the method reduces the amount of energy needed to create hydrogen fuel by 600%. The results are presented in the study “Sub-volt conversion of activated biochar and water for H2 production near equilibrium via biochar-assisted water electrolysis,” which was published in Cell Reports Physical Science.

The method uses a carbon-rich substance called biochar to decrease the amount of electricity needed to convert water to hydrogen. Combined with using solar power or wind to power the water-splitting process known as electrolysis.

“We are the first group to show that you can produce hydrogen utilizing biomass at a fraction of a volt,” said the researchers. “This is a transformative technology.”

Electrolysis represents the most expensive step in the hydrogen fuel lifecycle, representing about 80% of the cost. Recent advancements in producing hydrogen fuel have decreased the voltage required for water splitting by introducing a carbon source to the reaction. However, this process often uses coal or expensive refined chemicals and releases carbon emissions as a byproduct.

The UIC researchers modified the process to instead use biomass from common waste products as the carbon source. By mixing sulfuric acid with agricultural waste, animal waste, and sewage, they produced a slurry of biochar to be used in the reaction.

The team trialed several different inputs for biochar, including sugarcane husks, hemp waste, paper waste, and cow manure. All five inputs reduced the power needed to perform electrolysis, but the best performer, cow manure, decreased the electrical requirement by 600%, to roughly a fifth of a volt.

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With reduced voltage requirements, the UIC researchers were able to produce an electrolysis reaction with one silicon solar cell generating about 15 milliamps of current at 0.5 V, or less than the amount of power produced by an AA battery.

“It’s very efficient, with almost 35% conversion of the biochar and solar energy into hydrogen,” said Rohit Chauhan, the report’s co-author. Chauhan said the utilization rate of biochar represents a world record.

The research team said this utilization for biochar represents a new revenue stream potential for farmers, or an opportunity to become self-sustainable for energy needs.

Orochem Technologies Inc. sponsored the research and has filed for patents on the biochar-hydrogen process. The UIC team plans to test the methods at a larger scale. Stanford University, Texas Tech University, Indian Institute of Technology Roorkee, Korea University also participated in this study.

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