There are more than 12,000 abandoned coal mines across China, offering vast amounts of underground space and sophisticated infrastructure that could potentially be repurposed – and researchers have an idea about how to do just that.
The idea, from a team at the Shanxi Province Coal-based Resources Green and High-efficiency Development Engineering Center, is to use the tunnel and cavern networks for “agricultural experiments”, turning these spaces into farming labs.
Let’s get the obvious downsides out of the way first: There’s clearly no sunlight or rainfall underground, which is usually crucial for farming.
However, as the researchers outline in a paper published in China Mining Magazine, there are upsides too.
Subterranean environments can be carefully controlled, and are protected against fluctuations in the weather, ongoing climate change, and natural disasters.
“Against the backdrop of intensifying global climate change and growing agricultural demand in extreme and enclosed environments, exploring experimental agricultural models in coal mine underground spaces carries important scientific significance and engineering value,” write the researchers in their published paper.
That’s not to say this isn’t going to take a significant amount of work – or that all of those 12,000 mines can be set up as farming experiments.
The research team carried out a general assessment looking at structural safety, the feasibility of converting abandoned mines into agricultural units, and the practicality of managing light, heat, water, air, and carbon dioxide in these environments.
They also considered issues like ventilation and drainage.
The conclusion was that at least some of the mines would provide environments stable enough to test out new approaches to farming – approaches that might become increasingly important as the climate shifts.
“The results show that coal mine underground spaces possess the engineering foundation for constructing agricultural experimental units when the surrounding rock stability meets engineering specifications, and ventilation, drainage, and safety monitoring systems are complete,” write the researchers.
“Through artificial light sources and environmental control systems, underground spaces can realize the independent supply and precise regulation of key production factors such as light, heat, water, air, and carbon, thereby supporting the implementation of highly controllable agricultural experiments.”
Another bonus of farming underground is access to geothermal energy. The researchers suggest this could be tapped into as a sustainable heat source for crops, with far fewer greenhouse gas emissions.
What’s more, contaminated groundwater that leaks back into the mines and becomes contaminated – through sulfates, metals, and other particles – could be treated underground and reused for irrigation.
We’re not talking about full fields of crops, but rather research projects that test out different ways to grow food in different settings.
“The introduction of agricultural systems into the underground space of coal mines aims not to achieve traditional agricultural production, but rather to construct an agricultural scientific experimental platform for extreme and enclosed environments,” write the researchers (via Google Translate).
According to the South China Morning Post, the number of closed mines will be up to some 15,000 by the end of the decade. That represents around 7.2 billion cubic meters (254 billion cubic feet) of space going unused.
While plenty of challenges remain (and the researchers haven’t done any testing in the field yet), it’s at the very least a possibility. The feasibility study points to the Callio project in Finland, a successful mine conversion project, as an example of what’s possible.
Eventually, knowledge gained from farming underground could be used to inform future approaches to growing crops in extreme environments – whether that’s out in space or in remote areas of the world not suited to traditional agricultural systems.
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“Overall, coal mine underground spaces can serve as an important carrier for highly controllable agricultural experiments, providing a new approach for agricultural mechanism research in extreme environments and the reuse of underground space resources,” write the researchers.
The research has been published in China Mining Magazine.
