Canadian and Dutch researchers have published a paper arguing that metal fuels could provide a clean alternative to carbon fuels in situations where renewables are inappropriate.
“Using metal powders as recyclable fuels that store clean primary energy for later use is a very promising alternative solution,” said Jeffrey Bergthorson, mechanical engineering professor at McGill University in Montreal.
He said burning metal powders as fuel was well established in fireworks and solid fuel boosters in rockets but little work had been done in creating stable flames.
Using a custom-built burner, he and his team demonstrated that a flame can be stabilised in a flow of tiny metal particles suspended in air.
Once burned, they react with air to form stable, nontoxic solid-oxide products that can be collected relatively easily for recycling.
The next steps are to build a prototype burner and couple it to a heat engine then develop metal recycling processes that don’t involve CO2 emissions.
Bergthorson suggests iron could be the primary candidate for this purpose. Millions of tons of iron powders are already produced annually for the metallurgy, chemical and electronic industries. And iron is readily recyclable with well-established technologies, and some novel techniques can avoid the carbon dioxide emissions associated with traditional iron production using coal.
One of the paper’s co-authors is David Jarvis, head of strategic and emerging technologies at the European Space Agency in the Netherlands.
"We are very interested in this technology because it opens the door to new propulsion systems that can be used in space and on earth. The shift away from fossil fuels for vehicle propulsion is a clear trend for the future,” Jarvis said.
“While not perfected and commercialised today, the use of low-cost metallic fuels, like iron powder, is a worthy alternative to petrol and diesel fuels. If we can demonstrate, for the first time, an iron-fueled engine with almost zero CO2 emissions, we believe this would then trigger even more innovation and cost reduction in the near future."
Stabilised flames of different metal powders burning with air, compared to a methane-air flame. Image: McGill University.