Hydrogen production using only solar energy and agricultural waste

May 31, 2024Reviewed by Lexie Corner

A multi-institutional team led by engineer Meenesh Singh of the University of Illinois at Chicago has developed a novel technique for producing hydrogen gas from water using solar energy and agricultural waste such as manure or chaff. These findings were published in Cell Reports Physical Sciences.

This technique reduces the energy needed to extract hydrogen from water by 600%, opening up new possibilities for creating environmentally friendly, sustainable chemicals.

Hydrogen-based fuels are among the most promising sources of sustainable energy. However, producing clean hydrogen is an energy-intensive process that often requires coal, natural gas and significant amounts of electricity.

This approach uses biochar, a carbon-rich material, to reduce the amount of electricity required to convert water into hydrogen. The technique can reduce greenhouse gas emissions to zero by using renewable energy sources such as solar or wind power and collecting byproducts for other purposes.

We are the first group to show that hydrogen can be produced using biomass at a fraction of a volt. It’s a transformative technology.

Meenesh Singh, Associate Professor, Department of Chemical Engineering, University of Illinois at Chicago

Electrolysis, the process of converting water into hydrogen and oxygen, requires the use of electricity. On an industrial scale, fossil fuels are widely used to generate energy.

Recently, scientists lowered the voltage required to split water by incorporating a carbon source into the process. However, this method also uses coal or expensive chemicals and emits carbon dioxide as a by-product.

Singh and colleagues modified this procedure to use biomass from common waste products. They produce a slurry-like material known as biochar, with a high carbon content, by combining sulfuric acid with sewage, animal manure or agricultural waste.

The researchers experimented with several types of biochar made from sugar cane husks, hemp waste, paper waste and cow dung. When added to the electrolysis chamber, all five types of biochar reduced the power required to convert water to hydrogen. The most efficient product, cow dung, reduced electricity demand sixfold, to about one-fifth of a volt.

The energy requirement was low enough that researchers could power the process with a single, ordinary silicon solar cell, which produced about 15 milliamps of current at 0.5 volts. This is less than the output power of an AA battery.

It is very efficient, enabling the conversion of biochar and solar energy into hydrogen by almost 35%. These are world records; this is the highest result anyone has ever shown.

Rohit Chauhan, study co-author and postdoctoral fellow, University of Illinois, Chicago

To make the process zero, the carbon dioxide produced during the reaction must be collected. But Singh believes it could have both environmental and economic benefits, such as producing clean carbon dioxide to carbonate 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. This cheap way of producing hydrogen could enable farmers to become self-sufficient in meeting their energy needs or create new sources of income.

Nishithan Kani, co-author of the study and graduate of the University of Illinois at Chicago

Orochem Technologies Inc., the study sponsor, has filed patent applications for its biochar and hydrogen production techniques, and the UIC team intends to test these procedures on a large scale.

UIC graduate student Rajan Bhawnani co-authored the study. Other co-authors are from Stanford University, Texas Tech University, Indian Institute of Technology Roorkee, Korea University and Orochem Technologies Inc.

Magazine number:

Kani, North Carolina, et al. (2024) Subvoltage conversion of activated biochar and water for near-equilibrium H2 production via biochar-assisted water electrolysis. Cell Reports Physical Sciences. doi:10.1016/j.xcrp.2024.102013