Professor Louise Horsfall, Chair of Sustainable Biotechnology, says that a combination of necessity and ingenuity is giving the UK a global edge in harnessing microbes to valorise waste....
Metals are a big piece of the sustainable energy technology puzzle we need to solve for a successful transition to net zero. Batteries in electric vehicles depend on metals including lithium, cobalt and nickel. Rare-earth elements such as neodymium are essential for the powerful magnets in wind-turbine generators. And copper wires form the arteries of our increasingly electrified society.
Building the infrastructure for the energy transition hinges on a secure supply of these technology-critical metals, and that is driving a global race for these finite resources.
Engineering biology – applying engineering principles to biological processes and systems – offers a way to reuse what we have, and create new, clean, industrial processes.
While the US, with China hot on its heels, has the edge on engineering biology for therapeutics, the UK is leading in cutting edge ways to use microbes to valorise waste. We may not have the land area to grow the biological feedstocks required for the bioproduction of commodity chemicals, but instead the UK has lots of people and lots of waste, so is developing innovative circular economy processes.
For example, here at the University of Edinburgh, colleagues Stephen Wallace and Joanna Sadler are using E. coli bacteria to turn PET plastic bottles into paracetamol, vanillin, adipic acid and more.
In a similar way, my lab is using microbes to recover metals from waste, and to make mining more sustainable.
For example, half of the world’s palladium, mined in South Africa and Russia, is used in catalytic converters, where it turns carbon monoxide and hydrocarbons into less harmful gases, such as carbon dioxide and water vapour.
Palladium is also a catalyst in the chemical reactions used to produce pharmaceutical drugs and agrochemicals.
Bacteria can biosynthesise nanoparticles made of palladium, and we have found that these nanoparticles are far more catalytic than alternatives (chemically synthesised palladium nanoparticles, palladium on carbon and ionic palladium) at low temperatures and in water, making their use much more sustainable than current practises.
Furthermore, our experiments have shown that we can engineer the bacteria to make their nanoparticles even more catalytic than the naturally occurring kind, which increases efficacy and efficiency. Supported by Edinburgh Innovations, the University’s commercialisation service, we are working with industry on use cases for these processes.
Lithium-ion batteries in electric cars do not last forever and contain metals classed as critical by the UK Government’s 2024 Criticality Assessment. If we can’t recycle these batteries, electric vehicles become unsustainable. But we can! First, the metal-containing components of the batteries are dissolved by chemical or biological methods. Then the bacteria get to work, removing the dissolved manganese, and producing cobalt and nickel nanoparticles. Once these metals have been extracted, they could be used to build new batteries or used in other green technologies. Meanwhile, the remaining liquid is a lithium-rich brine, which is also useful for battery production. I’m working with a battery recycling company to engineer bacteria for this purpose.
President Trump is in interested in Greenland because rare earth metals like neodymium and terbium – used in electric motors, wind turbines and magnets - are stored in the rock there. These can be found in small quantities in Scotland too. We have been working on the bioleaching of Scottish granite – using microbes and biotechnology to extract these minerals instead of mining them.
Mining not only depends on a finite supply of metals, but also involves the blasting and processing of rock, which is extremely energy-intensive. Separating metal and rock chemically involves harmful substances such as sulphuric acid, but here again, bacteria can do the job.
Countries such as South Africa, Australia and Chile use bioleaching to mine gold or copper – by spraying the rock with water and bacteria and leaving them in big piles until the metals are released. The process also releases metals such as zinc and nickel, which have also recently been classified as critical in the UK. This is a big step forward and there is a clear opportunity for engineered bacterial strains to be much more effective and efficient.
Along with colleagues at Cranfield and Birmingham-led research hubs, Edinburgh researchers have proven what is possible. On an Innovate UK global expert mission to Canada recently, I made the point that we are past the creative idea stage and ready for collaboration. We know the technology works, we now need investment – public and private – to scale up and build the metal microbe factories of the future, that run on waste, and produce zero emissions.
This piece was initially published in The Engineer.
