Today, 55 per cent of the world’s population live in urban areas, a proportion that is expected to increase to 68 per cent by 2050. Projections show that urbanisation – the gradual shift in residence of the human population from rural to urban areas – combined with the overall growth of the world’s population, could add another 2.5 billion people to urban areas by 2050, with close to 90 per cent of this increase taking place in Asia and Africa, according to new United Nations figures. Overall food demand is on course to increase by more than 50 per cent, and demand for animal-based foods by about 70 per cent.
Several hundred million people in developing countries remain hungry. Nearly 240m people in sub-Saharan Africa, or one person in every four, lack adequate food for a healthy and active life, and record food prices and drought are pushing more people into poverty and hunger. Achieving food security in sub-Saharan Africa however, remains a great challenge. Climate change, a result of greenhouse gas (GHG) emissions, will have a severe impact on poor developing countries.
Holding warming below a 1.5°C increase would require meeting various climate change targets plus reforesting hundreds of millions of hectares of liberated agricultural land. In order to adapt to climate change we require a radical change in food production including 1) an increase in food production without expanding agricultural land; 2) reduced demand on agricultural land to protect and restore forests and peatlands; and 3) reducing GHG emissions from agricultural production. These measures will help to stabilise the climate, promote economic development, and reduce poverty.
To achieve these aims we will be required to reduce the food gap between now and 2050 by about 50 per cent, global agricultural land gap by about 600m ha and increased efficiency of yield production using intensive food farming and automation. Food production should be increased through yield intensification without conversion of forests, savannas and peatlands to agricultural land. In addition, the world’s ruminant-meat (i.e. beef) consumption would need to be reduced by 40 per cent. Also reducing GHG emissions from agricultural production sources, particularly enteric fermentation by ruminants, manure, nitrogen fertilisers, and energy use will be necessary.
Protected agriculture – cultivation of high-value vegetables and other horticultural crops in greenhouses – allows farmers to grow cash crops on small plots in marginal, water-deficient areas where traditional cropping is not viable. Worldwide, there’s an estimated nine million acres of greenhouses. Vertical farms are also used with the aim of increasing the amount of agricultural land by ‘building upwards.’ In other words, the effective arable area for crops can be increased by constructing a high-rise building with many levels on the same footprint of land. One approach is to employ a single tall glasshouse design with many racks of crops stacked vertically.
Greenhouses require a large amount of energy to control the growing environment. 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.
To address the challenges it will be necessary to develop new technologies for food production which could be used in different climatic and land conditions. A breakthrough approach has been taken by University of Nottingham academics Professor Saffa Riffat and Professor Yijun Yuan, who filed four patent applications in November 2018 for methods and systems of agricultural cultivation using shafts and modified tunnels for growing crops, a system they have dubbed ‘Deep Farm’.
‘A breakthrough for
intensive food production’
Most of the food we eat is transported by roads, sea and air, contributing to large CO2 emissions. For each calorie of food we eat, 10 calories of crude oil are used. As Deep Farms could be located close to urban centres, CO2 emissions due to transportation of crops would be reduced. Deep Farms would eliminate the use of mechanical ploughs and other farming machinery, thus reducing the burning of fossil fuels that cause climate change.
Deep Farms could be constructed with different opening geometries (e.g. circular, square and rectangular) and have depths of a few metres to several hundred metres. As they have a small land footprint, they could be constructed close to cities which would reduce the environmental and economic cost of food transportation. Deep Farms would allow crop production all year round, with up to 10 crop cycles per year compared to one to two cycles for conventional agriculture.
A variety of crops could be grown using hydroponic planters (plant roots fed with nutrient-rich water) or aeroponics (growing plants in an air or mist environment). LED units would enable photosynthesis in the absence of sunlight. Innovative water-saving systems and groundwater could be used to grow food even in desert climates. A major benefit of this approach is that crop production is largely unaffected by climatic or seasonal factors – one of the greatest limitations of conventional farming methods. Furthermore, using enclosed units isolated from each other, plant diseases and pests can be readily controlled with little or no application of chemical biocides.
Carbon dioxide is required for plant photosynthesis and Deep Farms are well suited for carbon capture from ambient air. An innovative CO2 capture system could be used to achieve the concentration levels required by plants. Use of carbon capture systems has the added benefit of reducing CO2 concentration in the environment, as additional carbon is adsorbed in materials in the ground space. Advanced control systems including sensors and remote controls could be used to monitor crop production. Automated systems such as robots could be used for crop planting and harvesting. Electricity generated from renewable sources and off-peak power could be used to power the LED lighting for plant photosynthesis. In addition, innovative daylighting devices using light rods or optical fibres could be used to supplement LED lighting.
Simple crop-harvesting systems using pulleys and grown in suspended baskets could be used in the Deep Farm. To be harvested the baskets would be pulled up, removing the necessity to work within the shaft but offering new job prospects for the urban communities where unemployment levels are high.
Deep 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 ground environment, in terms of temperature and humidity, is naturally suited to the growth of plants. Plants can thrive in an essentially closed environment with less oxygen and enriched levels of CO2 and water.
Deep Farms have many benefits including:
• Easily constructed using various drilling methods
• Can use absorption materials to capture CO2 from ambient
• Reduced dependency on cultivated land, climate and surface water resources
• More efficient utilisation of natural resources in crop production
• Improved security of crop production and reduced impact of natural and man-made factors
• Higher yields and greater cost efficiency
• Improved control over quality and food safety
• Removal of seasonal restrictions allowing production of crops all year round
• Can be used in areas with poor natural weather conditions, e.g. cold climates, and areas with low solar insolation
• Crops can be produced in desert, dry and water-deficient areas
• The impact of human conflict on crop production is reduced
• Crops can be grown close to highly populated areas.
It is estimated that a small Deep Farm can produce 80 tonnes of food per annum, and some of the crops can be ready for harvesting within three to four weeks. The amount of energy it would require is equivalent to that consumed by three UK homes.
Crops suited to deep farming methods including lettuces and leafy greens (e.g. kale and spinach), herbs, carrots, onions, peppers, aubergines, cucumbers, strawberries and different types of mushrooms. Deep Farms could be installed at various locations in or close to cities, and they would facilitate the supply of a wide range of fresh crops to the local population.
