University of Nottingham academics are exploring a new concept for subterranean farms as an alternative approach to large scale crop production.
The farms would be linked by a network of tunnels for intensive crop farming to feed rising urban populations. They could be established close to, or beneath, city centres to reduce transport costs and CO2 emissions, according to the researchers.
Cost-effective underground tunnels for crop planting could be constructed using new drilling techniques and these could be linked with existing coal mining and civil air defence tunnels, many of which are now abandoned, they suggest.
Professor Saffa Riffat, project lead and chair in Sustainable Energy at the Faculty of Engineering explains: “There are millions of redundant coal mines and tunnels in the world which could be linked to new tunnels for crop production. In the UK there are over 1,500 redundant coal mines, and in China, there are over 12,000 abandoned coal mines (0.6 million cu.m), 7.2 billion cu.m of tunnels and about one billion cu.m of civic air defence tunnels.”
Professor Yijun Yuan, Marie Curie Research Fellow at the University of Nottingham, and specialist in sustainable energy and mining engineering will work with Professor Riffat on the project, which will focus for the next two to three years on the potential for the concept in the UK and China.
It is anticipated that a variety of crops could be grown in the subterranean farms using hydroponic planters - with plant roots fed with nutrient-rich water. Coloured LED units would enable photosynthesis in the absence of sunlight.
Groundwater could be used directly or water could be condensed from ambient air. A major benefit of this approach is that crop production is largely unaffected by climatic or seasonal restrictions - one of the greatest limitations of conventional farming methods - allowing production of different kinds of crops all year round, according to the researchers.
Prof Riffat says: “Many crops are now being grown in greenhouses. Although this provides a controllable growth environment, greenhouses are heavy energy consumers. Vertical farms are a relatively recent adaptation of the traditional greenhouse and are suitable for use in cities, as their tall glass structures provide high crop yields on a small land area.
“However, vertical farming systems are expensive to manufacture and install, and require a large amount of water and energy for heating and cooling. They are also vulnerable to extreme weather conditions, wars and terrorism,” says Professor Riffat.
“Underground farms are not strongly affected by the seasons or climates, and are resistant to natural disasters, extreme weather, pests and diseases, man-made accidents and industrial pollution. In fact, the subterranean environment is naturally suited to the growth of plants. Plants need a closed environment with less oxygen and enriched levels of CO2 and water.
“In terms of the rationality of the biological chain and the biological space, crops are best located underground, leaving the ground surface for human and animal activities,” Professor Riffat adds.