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Cambridge University Science Magazine

Our world is undergoing an energy transition. Fossil fuels are being phased out as renewable energy paves the way to net zero. To drive this change, there is a rapidly increasing global demand for the materials of the future. Lithium is one of these materials, being a key component in Li-ion batteries — a crucial part of electric cars, alongside other commercial battery systems. With demand for these batteries increasing by the day, the need for lithium is expected to increase by over 300% by 2030. However, despite the central role of lithium in green technology, traditional lithium extraction is often damaging to our natural environment.

Australia is currently the world’s largest lithium producer, accounting for over half of the global supply. Here, lithium is mostly mined via hard-rock methods, where it is extracted primarily from a mineral called spodumene. Although this method is efficient for extracting lithium, it comes with many downsides. For example, the opencast mines have a large physical impact on the landscape and are associated with high carbon footprints due to the energy required to extract the rock and process the minerals.

Chile, the world’s second largest producer, extracts lithium through a very different process. Due to the high solubility of lithium, it is often found dissolved in subsurface fluids. These fluids are circulating in underground reservoirs beneath Chile, and miners pump this water to the surface where it evaporates under the harsh Chilean sun in artificial evaporation ponds. Unfortunately, this method is also problematic. Chile is a relatively dry country and, for the process to remain sustainable, the underground reservoirs must be recharged by rainfall. However, extraction rates are already outpacing recharge rates. This is having a serious impact on local communities, who are deeply opposed to new lithium extraction projects due to the relatively unknown future impact on their natural environment and drinking water. In addition, the evaporation ponds require vast expanses of land and, like hard-rock methods, have a large physical impact on the landscape, being easily visible from space.

Alongside the environmental issues associated with extraction, the global distribution of lithium reserves also causes problems. The US, EU, and UK are big players in the energy transition but lack the domestic lithium production to develop significant battery supply chains. Since shipping these raw materials across the world has a large environmental impact, a local source would be strongly preferred; however, typical lithium reserves in Europe are small and often very low-grade. This has historically prevented companies from developing them. Nowadays, the ever-increasing global demand, alongside more sophisticated extraction techniques, has brought these lower-grade deposits into the economic spotlight. The Jadar Valley in Serbia and Cinovec project in the Czech Republic are two sites currently being explored in Continental Europe. Here in the UK, the focus is on Cornwall.

Why Cornwall? The regional geology is distinct from the rest of the UK due to a large body of granite, called the Cornubian batholith, lying beneath much of the South West peninsula. This stretches from the Isles of Scilly in the west to Dartmoor in the east and is responsible for Cornwall’s rich mining history. Copper and tin deposits associated with the granite have been exploited for millennia. Of greater interest today, however, is that areas of this granite, particularly around the St Austell area, contain certain lithium-rich minerals. These minerals are micas (a category of mineral), specifically zinnwaldite and lepidolite.

Although the Cornish granite is considered low-grade for lithium on the global scale, interest is growing. Currently, there are a number of companies attempting to extract the lithium-rich micas from the granite and commercially produce lithium. Trial projects are currently mining small volumes of granite to test both whether this is feasible and sustainable, with the redevelopment of brownfield sites and the use of renewable energy in the extraction process. This has caught the attention of many investors as well as the UK Government. The Government is understandably keen to develop a domestic source of lithium and has funded a range of endeavours, such as Li4UK. This feasibility study involves the company Cornish Lithium and the Natural History Museum, and aims to secure a domestic lithium supply chain for the UK.

However, can lithium mining in Cornwall be truly sustainable enough to be labelled ‘eco’? And what is ‘eco-mining’ anyway? Traditionally, mining has been viewed in a negative light; stripping the planet of resources, leaving unsightly scars on the landscape, and emitting huge volumes of greenhouse gases into the atmosphere. Even though minerals are essential for society, the methods used to extract them have often caused tension between mining companies, environmentalists, and the wider public. However, significant technological advancements are now providing new, near carbon-neutral methods of extraction.

Alongside the traditional hard-rock extraction method, Cornish Lithium are trialling a new technique known as direct lithium extraction, or DLE. In 1864, during previous mining operations, it was noted that lithium-enriched geothermal waters were circulating deep below Cornwall. Cornish Lithium began drilling operations in 2019 and have managed to pump this water successfully to the surface and extract the lithium without the need for huge evaporation ponds. This constitutes a significant improvement in the environmental footprint of mining operations. Cornwall is not, however, the only place where this novel technique is being tested. For locations where significantly lithium-enriched brines are circulating, DLE provides an effective, green method for lithium extraction. Trials are taking place across the world, with test-phase extraction plants being built even in countries without a significant history of lithium mining, such as the US and Japan. DLE is also being trialled in Chile, in an attempt to find an alternative to the problematic evaporation ponds.

Many of the lithium-enriched brines also have the potential for use in geothermal energy. Fluids extracted from shallow depths of around 1 km are not hot enough for commercial geothermal electricity production, but the heat can still be used to help power the extraction of the lithium itself. Meanwhile, deep fluids from over 5 km below the surface can be hot enough for use in full-scale geothermal energy projects, with the electricity produced helping to make the lithium extraction process an overall net-zero venture.

If this new method proves effective, it could help to decarbonise the lithium extraction process, eliminate the environmental impact of evaporation ponds, and allow the commercial production of lithium in areas where extraction was previously uneconomical. This last point is particularly important. Not only does this allow the creation of large-scale domestic battery production lines, but it significantly reduces the carbon footprint of shipping the raw materials across the globe. Lithium extraction directly from geothermal waters is set to revolutionise the lithium extraction industry and help to meet the global demand necessary for the energy transition.

Matthew Morris is a MASt student in earth sciences at Queens’ College.