Reducing contamination in biochar

Award winner Ibrahim Gbolahan Hakeem has been studying the recovery of heavy metals from biosolids and their impacts on creating biochar through pyrolysis. How can he help the water industry improve using his research?

Award winner Ibrahim Gbolahan Hakeem has been studying the recovery of heavy metals from biosolids and their impacts on creating biochar through pyrolysis. How can he help the water industry improve using his research?

In late October, the Australian Water Association’s (AWA) Victorian Water Award winners were announced at a glittering ceremony. Several organisations and individuals were recognised for their inspiring leadership, innovative research, programs, and infrastructure projects.

Among the winners was Ibrahim Gbolahan Hakeem, a PhD student at the Royal Melbourne Institute of Technology (RMIT) University. He’s now a postdoctoral researcher at RMIT. Hakeem is also part of the Australian Research Council (ARC) Biosolids Industrial Transformation Training Centre and the Water Research Australia (WaterRA) research leadership program.

Hakeem completed his Bachelor of Engineering at Federal University of Technology Minna, focusing on chemical engineering. It’s one of the few specialised universities of technology in Nigeria. Following the completion of his bachelor’s degree, Hakeem received a Commonwealth Shared Scholarship to attend the University of Bath in the United Kingdom. He completed his Master of Science, majoring in sustainable chemical engineering.

“I had a different direction in mind when I first started my bachelor’s degree,” said Hakeem. “Nigeria has a significant oil, gas, and petrochemical industry, so I originally thought I’d be heading down that path. However, once I entered the program, I got to understand more of what chemical engineering can do.”

This led to Hakeem’s interests changing, with a new focus on process design and developing technologies for waste management. However, the shift to the water industry came about during the completion of his Masters.

“My Masters’ project focused on the conversion of aquatic biomass using hydrothermal processes,” he said. “I was specifically looking at microalgae, water hyacinth, seaweed, and related materials. It was at this point I started studying water-generated waste resources with more focus on sewage sludges and wastewater treatment residues.”

Australia and the water sector

Once Hakeem moved to Australia, he studied at RMIT to complete his PhD. His work focused on developing integrated chemical-thermal processes for converting biosolids to high-quality biochar.

“I’ve just finished my PhD on the development of new valorisation techniques and improvement of pyrolysis process for the production of biochar, bioenergy, and chemicals from biosolids in a biorefinery context,” he said. “There’s been a lot of interest in the work I have done by the industry. Our research group here at RMIT, led by Professor Kalpit Shah, has significantly impacted the water industry.”

Studying under Kalpit Shah, Hakeem has grown from strength to strength.

“My professor has been working with the Australian water sector for some years now,” Hakeem said. “I’ve been working in the biosolids training centre, which has been looking at developing solutions for biosolids resources in Australia.”

The industrial transformation training centre seeks to have the water industry work in conjunction with academia to find long-lasting solutions to water problems.

“Working in the centre has allowed me to work with water professionals across the country, create that impact and get their perspective in the initial stages of my work,” he said. “The water industry has been a great collaborator of our work.”

Removing contaminants from biosolids

Removing contaminants, such as heavy metals, from biosolids is important for water utilities wanting to increase the sustainability of their operations.

“When I started my PhD, I was looking at that topic in a broad sense,” Hakeem said. “When I started to develop the scope and identify the gaps in which I could have the greatest impact, I sensed that the water sector was a bit sceptical about the opportunities that could arise from the non-agricultural use of biosolids, particularly those involving thermal treatment such as pyrolysis.”

One of the biggest concerns was around legacy contaminants such as heavy metals. There was also concern about the growing range of emerging contaminants, such as PFAS and microplastics.

“This drove my interest in exploring alternative treatment methods,” he said. “Pyrolysis is one of the developments that is gathering significant traction in the water space. The industry is now in a position to develop pyrolysis at large scale.”

Pyrolysis is the treatment of organic materials through heat under an oxygen-deficient environment to create biochar, a carbon-rich solid residue. Biochar is the lightweight black residue (or char) that remains after the pyrolysis of biomass and can have applications, including soil amendments, fertilisers, adsorbents, and energy storage. While most contaminants are destroyed in the intense heat (typically between 300 and 650 degrees Celsius), there is a range of heavy metals and inorganic contaminants that remain stable. Those contaminants remain in the biochar but at a higher concentration due to a significant reduction of organic matter.

“The goal is to make pyrolysis technique more sustainable for the water industry,” Hakeem said. “We thought about whether we should remove the heavy metals before or after pyrolysis. My research focused on removing the heavy metals from the biosolids before pyrolysis. That produces biosolids free of contaminants, improving the overall quality of the derived biochar for land application.”

Pyrolysis in action

Hakeem recently spent time conducting some research at the pyrolysis plant at the Melton Recycled Water Plant. The pyrolysis plant (known as PYROCO) was a combined effort between South East Water, RMIT University, Greater Western Water and the Intelligent Water Networks (IWN).

“I wanted to study how biosolids generated from different types of wastewater treatment facilities will behave during pyrolysis,” he said. “One of the processes developed within my PhD has been to enhance the pyrolysis conversion of biosolids by subjecting them to mild acid pre-treatment. I found that the selective removal of heavy metals and ash-forming elements during the pre-treatment process facilitated organic matter conversion to quality biochar and bioenergy. The raw and treated biosolids reacted differently during pyrolysis, creating different benefits to product yields and properties.”

What Hakeem was able to determine from the trials is that biosolids that contain more ash, minerals and heavy metals are far more difficult to deal with because they have less energy content to convert. That means Hakeem’s research will be pivotal in removing these contaminants before undergoing pyrolysis. It will improve the process efficiency and product quality.

“I believe that pyrolysis promises to offer many benefits to the water industry,” said Hakeem. “We’re getting some serious interest from the entire sector, and there’s a lot of excitement there. The commercialisation prospects of the PYROCO technology are growing fast, including the deployment of mobile pyrolysis plants. They can install that on-site for the sustainable conversion of biosolids and biowaste. That creates a localised market for the products.”

Award winner

As the Victorian winner of the Student Water Awards, Hakeem said it was an honour to have received the award.

“It shows our commitment and dedication to researching wastewater treatment and biosolids management,” he said. “I felt so celebrated. My supervisor was also very proud of the work we are doing for the Australian water sector, and to be recognised for that. We are looking forward to the next stage, which will be the national final.”

That national final will take place during OzWater’24 in Melbourne from Tuesday, 30 April, to Thursday, 2 May. The award will be one of several that will be given out at the event.

Trends and the future

Hakeem believes that the Australian water sector is interested in the resourceful utilisation of biosolids and their pyrolysis to biochar.

“Although biochar has been a feature of the European and North American water sectors for several years,” he said. “The interest in Australia has been incredible, particularly given the increasingly stringent regulations around biosolids management. These regulations consider applications, emerging contaminants, resource recovery, and a range of other issues.”

In the eyes of Hakeem, these are new drivers that are pushing the water sector to consider its options when it comes to biosolids. The goal is to improve the management of their biosolids, destroy contaminants, and generate high-value products in a circular economy approach.

When it comes to his future, he wants to remain in the biosolids pyrolysis research. Many areas need work, and Hakeem intends to be at the forefront.

“I see myself working in this space and developing much-needed technological solutions to challenging water sector problems.”

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