Discarded shrimp shells can soon become more than just kitchen waste. Scientists in Singapore have developed a process that converts organic waste into hydrogen fuel, protein for aquaculture feed and calcium carbonate, a material used in products such as cement and antacids.The technology was developed by electrochemical engineer Li Hong and his team at Nanyang Technological University (NTU). It uses carbon-rich waste to produce what researchers describe as ‘carbon-negative’ hydrogen. The purpose of this process is to remove more carbon dioxide than it produces from the atmosphere by preventing organic waste from going into landfills and creating useful products from it.The lab-scale system is still a long way from commercial production, but the researchers say it offers a new approach to tackling two major challenges simultaneously: Reducing waste and finding clean alternatives to fossil-based energy and industrial materials.
Converting seafood waste into hydrogen
Most hydrogen produced today comes from a process that uses natural gas and steam, known as “gray hydrogen”. Clean versions, including “green hydrogen”, rely on renewable electricity to split water into hydrogen and oxygen.Lee’s team took a different approach. Instead of using water as the main raw material, the researchers adapted electrolysis technology to work with organic waste such as discarded shrimp shells.Traditional water electrolysis requires large amounts of energy and produces oxygen, which can make the system more difficult to manage. The Singapore team’s approach uses organic materials that react more easily with the help of catalysts, reducing energy requirements while avoiding the oxygen-related challenges of conventional electrolysis.The process begins by crushing shrimp shells to produce a red colored solution. Using ball milling equipment, researchers separate calcium carbonate from the mixture. The remaining organic acid and ammonia are then put into an electrolyzer installed on the roof of the university.Powered by five solar panels, the electrolyzer works like a battery, with electrodes placed on opposite sides of a tank and a membrane separating them. As electricity passes through the organic mixture, hydrogen gas is released and collected.In their laboratory setup, the team produced 14 liters of hydrogen gas per hour.
A waste system designed to produce more than fuel
Hydrogen is only part of this process. After electrolysis, the remaining biomass is transferred to a bioreactor where phototrophic purple bacteria are added.These bacteria ferment the leftover matter into a protein-rich product that can potentially be used as feed for farmed seafood, including shrimp.Researchers say this could help reduce reliance on wild-caught fish for aquaculture operations. By creating feed from waste, the system aims to create a circular process where seafood waste can eventually support seafood production again.“This process ‘closes the loop from waste to food,’ and it employs a waste-to-wealth mentality,” Lee says.The third major product is calcium carbonate, which can replace some of the quarried limestone used in cement production. The global cement industry produces approximately 4.2 billion metric tons of cement each year, and reducing demand for mined limestone could help reduce environmental impacts.Juan Carlos Serrano Ruiz, a chemist and engineer at Universidad Loyola in Spain who was not involved in the research, described the approach as a “very clever” solution to a difficult problem in hydrogen production.“I was really surprised by the degree of integration,” he says.
Moving from laboratory success to commercial reality
The technology has attracted attention, but researchers acknowledge that scaling up will be difficult. The current system is about half as efficient as commercial green hydrogen technologies. Improving production rates will be necessary if the process is to compete economically with existing hydrogen methods.Green hydrogen currently costs more than hydrogen made from natural gas, with prices strongly influenced by electricity costs and government support. Li’s team estimates that a pilot plant capable of processing 200 metric tons of shrimp shells would spend more than half of its operating costs on electricity.Selling multiple products can help improve the economy. Instead of relying solely on hydrogen revenues, companies can also generate income from calcium carbonate and protein products.“Selling hydrogen along with other products from your process, whether calcium carbonate or protein, can balance the economics,” says Alex Pierce, a materials scientist at Modern Hydrogen in Washington state. “It’s both powerful, because you get revenue from it, but it’s also a little more complex, because you’re linking two markets together.”
Technology may advance beyond shrimp shells
Although the first demonstration used seafood waste, Lee says the process can be adapted to many types of biomass.“It is a very versatile technology,” he says, “suitable for a variety of waste types, including cardboard, vegetables, hay, corn and residues from industries such as palm oil, forestry, sugar and brewing.”For Serrano Ruiz, the value of the technology lies in its ability to recycle organic waste into useful materials.“I will sell this technology as a way to recycle biomass, to convert biomass into something useful,” he says.Two companies are already exploring commercial applications. London-based Key Hydrogen, founded in 2022, is using a modified version of the technology to process biomass waste from forestry, agriculture and breweries. The company aims to produce hydrogen and pure carbon dioxide, which is then sold to an industry partner to create a sustainable fuel.Another company is investigating whether this process can be used to recycle carbon from sewage sludge.
challenge to move forward
Before the technology can deliver major environmental benefits, researchers say several hurdles must be overcome. Companies will need reliable supplies of biomass waste, demonstration plants, and markets that support the sale of the resulting products.The carbon-negative claim would also require independent verification on an industrial scale. Laboratory results do not always translate directly to commercial operations, especially for complex biological and chemical systems.“With biomass, you always have the hurdle of making this thing big and profitable at the same time,” Serrano Ruiz says.