The world is generating vast quantities of waste, much of which is biodegradable, organic matter – and while we can use established technologies like anaerobic digesters to turn it into gas, we’re far less effective at putting that gas to good use. However, a new invention from a team led by Professor Song Chunshan, Dean of The Chinese University of Hong Kong (CUHK)’s Faculty of Science and Wei Lun Professor of Chemistry, promises to take the next crucial step.
Their integrated biowaste-to-green fuel generator transforms unwanted waste into one of the most valuable resources on Earth: energy. Specifically, it starts with biowaste, in the form of biogas, and transforms it into green fuel.
“Organic waste is a growing environmental challenge,” says Professor Song. “Large amounts of kitchen waste, livestock manure and municipal sludge from wastewater are used to generate biogas that is often flared or burned. Our generator addresses that.
“The key innovation separating it from traditional biowaste reactors, such as anaerobic digesters, is that conventional systems stop at biogas production, which is then gasified at high temperature or burned for heat or electricity. That approach is inefficient and releases carbon dioxide, harming the environment. Our technology instead converts biogas into liquid fuels, reducing carbon emissions.”
Beyond biogas: two key innovations
Awarded a Gold Medal with Congratulations of the Jury at the 51st International Exhibition of Inventions Geneva in March, the generator achieved two major technological breakthroughs:
1. Advanced gas purification
Raw biogas is typically composed mainly of methane and carbon dioxide, but it contains impurities that need to be filtered out. The generator employs a new method for doing so, passing the biogas through a bed made of sorbents – materials that adsorb the impurities (or make substances stick to the material’s surface). The concept of using sorbents in this context was first proposed by Professor Song over two decades ago. His team has since developed high-performance, durable sorbents capable of operating effectively even in humid, impurity-rich conditions.
“Our team is the first to incorporate this formulation into a fully integrated, standalone generator,” Professor Song explains. “The innovation lies in both the sorbents’ high performance and stability under humid, impurity-laden biogas conditions.”
2. Low-temperature plasma catalysis
The second innovation is a low-temperature plasma catalytic conversion process, which uses highly energised gas (plasma) to transform purified biogas into green fuel. Unlike traditional methods that require temperatures exceeding 700°C and high pressure, this system operates at near-ambient temperature and atmospheric pressure, significantly reducing energy consumption. The synergy between plasma and advanced catalysts further enhances conversion efficiency.
Versatile feedstock for flexible, large-scale use
The system is designed to use gas from organic waste as its feedstock – the material it’s fed with. The waste in question could be anything: leftover food, livestock manure, agricultural crop residues, wastewater treatment sludge or landfill gas.
“Any anaerobic digestion process that produces a methane-carbon dioxide gas mixture can serve as a viable feedstock source for our generator,” says Professor Song. “Our team’s research has demonstrated that the reaction conditions can be tailored to accommodate different biogas compositions from various sources, so feedstock variability is not an obstacle.”
Designed for a low-carbon future
The system is also modular and scalable, making it suitable for applications ranging from small farms to large municipal facilities. Depending on what the user wants, it can be used to make methane, green methanol, sustainable aviation fuel or chemicals such as acetic acid or syngas – in a process that takes just a matter of seconds.
The generator is powered by any source of low-carbon electricity and, unlike traditional high-temperature catalysis, it can be switched on and off instantaneously. This means it works well with sometimes intermittent sources of renewable power such as solar and wind. It could potentially even power itself, with some of the biogas diverted into a turbine and used for the plasma generator.
From lab to industry
The research team is now advancing towards industrial deployment. To support commercialisation, they have established a start-up, PineRiver Technology, which is currently seeking industrial and business partners and raising funds in order to advance this new technology into the commercial operation in the near future.
Professor Song identifies two major groups of potential users: “Producers of biogas such as large-scale agricultural and livestock operations that face stringent environmental regulations and high waste management costs can use our generator to convert a liability into a revenue stream. Second, food waste and municipal waste treatment facilities and maritime fuel suppliers are potential key users. Demand for green methanol is growing rapidly. Our distributed generator model allows the production of this fuel exactly where waste is generated or where fuel is needed, eliminating the costly transportation of low-value biogas.”
