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Researchers at UNSW Sydney have introduced an innovative zero-emissions technology that repurposes solar panels to convert nitrate wastewater into ammonium nitrate, a key ingredient in fertilisers. This new approach not only addresses the environmental challenges associated with traditional ammonia production but also offers a sustainable solution for supporting global agriculture.
The conventional method of producing ammonia, an essential component in fertilisers, is energy-intensive and generates significant greenhouse gas emissions. The process typically requires high temperatures, ranging from 400 to 500 degrees Celsius, and high pressure, both of which are achieved by burning fossil fuels. This has made ammonia production a major contributor to global carbon emissions. However, a team of engineers at UNSW, led by Scientia Professor Rose Amal and Professor Xiaojing Hao, have developed a novel system that could revolutionise this process by harnessing solar energy in a more eco-friendly manner.
The UNSW team has repurposed a traditional silicon solar panel, converting it into a device that functions similarly to an artificial leaf. This system, which utilises a photoelectrocatalytic (PEC) process, generates ammonium ions from nitrate-containing wastewater. The core of this technology lies in a nano-structured thin layer of copper and cobalt hydroxide applied to the solar panel, which acts as a catalyst to drive the necessary chemical reaction.
Their research, recently published in the Journal of Energy and Environmental Science, outlines the potential of this system to produce ammonium nitrate without the harmful emissions associated with conventional methods. Lead author Chen Han, along with Dr Jian Pan, a DECRA Fellow, and the rest of the team, have constructed a 40 cm² artificial leaf system on the roof of the Tyree Energy Technologies building at UNSW. This prototype has successfully generated enough ammonium ions to meet the fertilisation needs of 1.49 m² of cropland.
The implications of this development are significant. By operating at ambient conditions and relying solely on sunlight, this system eliminates the need for the high temperatures and pressures typically required for ammonia production. This not only reduces the carbon footprint of the process but also offers a decentralised solution, allowing for on-site production of ammonium in agricultural areas. Such decentralisation could further decrease CO2 emissions by reducing the need for the transportation of fertilisers.
The photoelectrocatalytic process developed by the UNSW team mimics the natural photosynthesis in plants, where sunlight, water, and carbon dioxide are converted into oxygen and energy. In this case, the solar panel acts as an artificial leaf, using sunlight and nitrate-rich wastewater to produce ammonium nitrate. This innovative approach combines the expertise of UNSW’s School of Photovoltaics & Renewable Energy Engineering and their School of Chemical Engineering to turn waste into a valuable commodity.
The researchers have developed an efficient catalyst with specialised nanostructures, which has been integrated into a conventional silicon solar panel. This combination has resulted in a highly effective process for producing ammonia. The system’s ability to generate sufficient ammonia for fertiliser use demonstrates its potential viability in real-world applications, though the team acknowledges there is still room for improvement.
In addition to producing ammonium, the researchers hope that the treated wastewater can be repurposed for irrigation, further supporting crop growth. However, Professor Amal notes that the wastewater used in the system must first be processed to remove organic matter and particulates before conversion.
Looking ahead, the team is eager to collaborate with industry partners to scale up the technology and further refine the process. Their goal is to develop a full-scale commercial system using traditionally sized solar panels, which could play a crucial role in meeting emissions targets for 2030 and 2040, and ultimately achieving Net Zero by 2050.
This breakthrough represents a significant step toward cleaner and greener ammonia production, with the potential to drastically reduce CO2 emissions and contribute to global sustainability efforts.
