The new method produces hydrogen from solar energy and agricultural waste

Engineers at the University of Illinois at Chicago helped design a new method of producing hydrogen gas from water using only solar energy and agricultural waste such as manure or chaff. The method reduces the energy needed to extract hydrogen from water by 600%, creating new opportunities for sustainable, climate-friendly chemical production.

Hydrogen-based fuels are one of the most promising sources of clean energy. However, producing clean hydrogen is an energy-intensive process, often requiring coal or natural gas and large amounts of electricity.

In an article for Cell Reports Physical Sciencesa multi-institutional team led by UIC engineer Meenesh Singh presents a new process for producing green hydrogen.

This method uses a carbon-rich substance called biochar to reduce the amount of electricity needed to convert water into hydrogen. By using renewable energy sources such as solar or wind energy and capturing byproducts for other uses, the process can reduce greenhouse gas emissions to net zero.

“We are the first group to show that you can produce hydrogen using biomass at a fraction of a volt,” said Singh, an associate professor in the department of chemical engineering. “It’s a transformative technology.”

Electrolysis, the process of splitting water into hydrogen and oxygen, requires electricity. On an industrial scale, fossil fuels are usually needed to generate this electricity.

Recently, scientists lowered the voltage required to split water by introducing a carbon source into the reaction. However, the process also uses carbon or expensive chemicals, and the byproduct is carbon dioxide.

Singh and colleagues modified this process to use biomass from regular waste instead. By mixing sulfuric acid with agricultural, animal waste or sewage, they create a carbon-rich slurry-like substance called biochar.

The team experimented with different types of biochar made from sugar cane husks, hemp waste, paper waste and cow dung. When added to the electrolysis chamber, all five varieties of biochar reduced the power needed to convert water to hydrogen. The best of them, cow dung, reduced electricity demand sixfold, to about one-fifth of a volt.

The energy requirement was low enough that researchers could power the reaction with a single standard silicon solar cell producing about 15 milliamps of current at 0.5 volts. This is less than the amount of energy produced by an AA battery.

“It is very efficient, with almost 35% converting biochar and solar energy into hydrogen,” said Rohit Chauhan, co-author and graduate student in Singh’s lab. “These are world records; that’s the highest anyone has ever demonstrated.”

For a process to be net zero, it must capture the carbon dioxide produced in the reaction. But Singh said it could also have environmental and economic benefits, such as producing pure carbon dioxide to fuel carbonated drinks or converting it into ethylene and other chemicals used in plastic production.

“It not only diversifies the use of bio-waste, but enables the clean production of chemicals other than hydrogen,” said UIC graduate student Nishithan Kani, co-author of the paper. “This cheap way of producing hydrogen could allow farmers to become self-sufficient in their energy needs or create new sources of income.”

Orochem Technologies Inc., which sponsored the research, has filed a patent application for its biochar and hydrogen production processes, and the UIC team plans to test these methods on a large scale.

In addition to Singh, Kani and Chauhan, UIC doctoral student Rajan Bhawnani co-authored the paper. Other co-authors are from Stanford University, Texas Tech University, Indian Institute of Technology Roorkee, Korea University and Orochem Technologies Inc.