Scientists boil clean hydrogen from agricultural waste using 600% less energy

Rising greenhouse gas emissions and recent climate change indicators have led to increasing demand for a transition from fossil fuels to renewable energy sources.

Hydrogen is one of the most promising options for an emission-free energy carrier. It is a sustainable energy source that does not emit carbon dioxide when releasing energy.

In a further initiative in this area, researchers at the University of Illinois at Chicago (UIC) have developed a procedure to produce hydrogen gas from water using only solar energy and agricultural waste such as manure or chaff.

By reducing the energy needed to extract hydrogen from water by 600 percent, the technique opens up new possibilities for creating environmentally friendly and sustainable chemicals, according to the team.

The journal published details of a study conducted by researchers on this topic Cell Reports Physical Sciences.

Hydrogen from biochar

Hydrogen-based fuels hold great promise as a clean energy source. However, the process of producing clean hydrogen is energy-intensive and often requires large amounts of electricity, coal or natural gas.

To solve this problem, a team led by UIC engineer Meenesh Singh developed a new process for producing green hydrogen. The researchers used a substance called biochar, which is high in carbon and reduces the amount of electricity needed to convert water into hydrogen.

Biochar is produced by high-temperature carbonization processes such as pyrolysis, gasification and hydrothermal carbonization. It can be produced both on a large industrial scale and on a small farm scale.

The team says that by using sustainable energy sources such as wind and solar power and recovering waste products, the procedure could achieve net zero greenhouse gas emissions.

“We are the first group to show that you can produce biomass using hydrogen at a fraction of a volt. This is a revolutionary technology,” Singh, an associate professor at UIC’s Department of Chemical Engineering, said in a statement.

Electrolysis, which splits water into hydrogen and oxygen, requires electricity. The industrial production of this electricity usually requires fossil fuels.

Recently, scientists were able to lower the voltage needed to split water by adding a carbon source to the process. However, this method produces carbon dioxide as a byproduct and uses carbon or expensive chemicals.

Singh and colleagues adapted this procedure to use biomass from common waste materials. By adding sulfuric acid to sewage, animal manure or agricultural waste, biochar, a carbon-rich sludge, was obtained.

Efficient green hydrogen

The group experimented with several forms of biochar derived from cow dung, paper waste, hemp waste and sugar cane husks. When added to the electrolysis chamber, all five types of biochar reduced the energy needed to convert water to hydrogen. Cow dung was the best; this reduced the need for electricity by a factor of six, to about one-quarter of a volt.

According to the researchers, due to its low energy requirement, the reaction can be powered by a single conventional silicon solar cell, which can provide a current of about 15 milliamps at 0.5 volts. That’s less energy than an AA battery can generate.

“It is very efficient, converting biochar and solar energy into hydrogen by almost 35 percent. These are world records; this is the highest result anyone has ever shown,” said Rohit Chauhan, co-author of the study and a graduate student in Singh’s lab.

Capturing the carbon dioxide produced in the reaction is essential to making the process net-zero. Singh noted that this approach could have environmental and economic benefits, including the production of clean carbon dioxide for carbonation and its conversion into ethylene and other chemicals used in the production of plastics.

The team notes that the method enables the clean production of compounds other than hydrogen and expands the use of bio-waste. “This low-cost way of producing hydrogen could enable farmers to become self-sufficient in meeting their energy needs or create new sources of income,” said Nishithan Kani, study co-author and UIC graduate student.

The team has filed patents for research into biochar and hydrogen production and intends to test these methods on a large scale.