How could rhubarb possibly help with the energy transition?

One of the most important aspects of the energy transition is the production and recycling of the materials which are used in the transition.  These materials range from the rare earth elements used in high-powered magnets to the lithium, aluminium, and a whole host of other important elements used in batteries.  Inevitably, a lot of this material will need to be mined and there are lots of companies, such as Weir and Sulzer, doing great work in improving the efficiency of the machinery used in the mining operations.  Even so, once the materials have been mined, processed, and have entered the material chain, it is important that they are recycled so that they are kept within a circular value chain.  Proper recycling reduces the need to produce virgin materials and also helps to insulate markets from economic and political impacts.

So where does rhubarb fit in?  Well, in work funded by the Swedish Energy Agency, BASE Batteries Sweden, Vinnova and using car batteries from Volvo cars, researchers at Chalmers University of Technology in Sweden have developed a process which minimises the loss of valuable raw materials such as nickel, cobalt, and manganese, all key battery materials, and which allows for 100% recovery of aluminium and 98% recovery of lithium using a chemical found in the leaves of rhubarb, namely oxalic acid. 

In this process, black mass, which is the crushed remnants of batteries, is taken and aluminium and copper are extracted using oxalic acid in a first step, followed by the subsequent removal of the other valuable materials.  This is the reverse of the existing method where these materials are removed towards the end of processing and reduces the loss of lithium.  The reduction in the loss of lithium is because it is removed in an initial step, whereas when it is removed in later steps, a small percentage of lithium is lost at each stage.  Reducing the number of stages before the lithium is removed therefore reduces the total loss of lithium.  Oxalic acid is an organic acid which is highly toxic and is the reason why rhubarb should never be cooked in an aluminium or copper pan since it attacks these metals.  Oxalic acid has biological sources, so could be a cheap and renewable way of extracting value from old batteries.  Perhaps the leaves from the “Rhubarb Triangle” in Yorkshire could become a valuable commodity in the UK's energy transition.

Every improvement in the way that materials can be recycled is a step in the right direction.  Every country in the world will be using battery recycling technology in the near term, so it is important for nations to encourage and invest in this technology now so that their economies can be more self-sustaining with regards to critical materials, which provides both economic and environmental benefits.  Who knows, this may also be an unexpected boost to the rhubarb industry!