Feeding the projected 2050 world population of about nine billion people will require global food production to be increased by some 70 per cent between now and then. But current land-based systems for food production cannot meet this extra demand. The problem is exacerbated by rising sea levels caused by climate change. Land area reduction due to inundation and coastal erosion will have a major impact on the availability of agricultural land for food production, with small islands being especially vulnerable.
To use less land, farms could be spread vertically rather than horizontally. This ‘vertical farms’ approach uses multi-layer greenhouses or skyscraper towers to intensify food production. With a controlled climate involving LED lighting and a closely monitored water/nutrient supply, these farms can produce multiple crops and high yields. But there is an option.
Marine agriculture has already been explored to ensure future food security. Ocean Reef Group in the USA proposed growing plants in pods (biospheres, each of which can hold around 22 plant pots) on the seabed. The project is interesting but is not viable for large-scale food production.
A fisherman, Bren Smith has developed a vertical ocean farm which uses a water column to grow a variety of species such as sugar kelp, oysters, mussels and scallops. Indeed, some countries like China and Thailand have been practicing aquaculture for many years. In the UK, salmon from fish farms is already a staple of our diet. In fact, recently aquaculture surpassed wild fishing as the primary source of protein from the ocean. However, these types of farms are not suitable for crop production. Farmers in Bangladesh survive the monsoon using an ancient technique of building floating farms that rise and fall with swelling waters.
Floating Deep Farms
Turning to the seas could be one solution for crop production to ensure the human population is adequately fed in the coming decades. A breakthrough has been made by University of Nottingham academics Professors Saffa Riffat and Yijun Yuan, who filed five patent applications in November and December 2018 claiming novel cultivation technology based on using Deep Farms in land, seawater and rivers.
Floating Deep Farms use large vertical shafts submerged in sea water near coastal areas. The shaft is sealed at the bottom end and is covered by a dome. A variety of crops can be grown using hydroponic planters (plant roots fed with nutrient-rich water) or aeroponics (growing plants in an air or mist environment). LED units provide illumination at appropriate wavelengths to maximise photosynthesis with minimum power input replacing sunlight. A major benefit is that crop production is largely unaffected by climatic or seasonal factors, which is one of the greatest limitations of conventional farming methods. Furthermore, enclosed Floating Deep Farms allow plant diseases and pests to be readily controlled with little or no application of chemical biocides.
The engineering knowhow to build marine vertical shafts is already available from the off-shore oil, gas and wind energy industries. Indeed, Floating Deep Farms could be integrated with wind turbines to power the LED lighting and other systems necessary for crop production. Such installations would not be subject to seasonal light variation, continuing in production throughout the year. Unlike present off-shore wind farms supplying renewable energy, Floating Deep Farms could be sited in deep water far from the coast since their locations would not be limited by power cables. Crops could be delivered to land by electrically powered ships charged by wind energy. It is also tempting to suggest that Floating Deep Farm installations might also have a secondary function of capturing discarded plastic.
Tide and wave energy could also be used for powering Floating Deep Farms. Obviously, these would be inshore. Tidal power might be preferable to PV, especially because they can be available day and night. Would integrated Deep Farms change the economics of barrages such as those proposed for the Severn Estuary?
Floating Deep Farms could be combined with towers which could be used for housing or offices. Such integration could be used in coastal areas.
About 70 per cent of the earth is covered with seawater. The fresh water required by the Floating Deep Farm can be created through a simple seawater evaporation desalination unit driven by a combination of solar energy and waste heat from LED lights. It is anticipated that much of the fresh water will be recycled, so, after initial charging, only a limited quantity of “make-up” water will be required. The quantity of water required will be reduced by 80 per cent compared to conventional land-based agriculture.
Unlike conventional greenhouses and vertical farms, which rely heavily on heating and cooling systems to regulate the temperature, the submersion of the Deep Farm into seawater offers a stable temperature throughout the year. The diurnal fluctuations in solar radiation and temperature that limits the productivity of many plants will be eliminated by the closed environment of Floating Deep Farms.
For coastal installations, various aesthetic design approaches could be used to make Floating Deep Farms blend with the surrounding environment and also to avoid any impact on communities which often rely on fish for food and as a source of income. The Floating Deep Farms can also be designed to incorporate aquaculture for fish and other species (eg scallops and mussels). This will allow oxygen generated by the plants to be fed directly into the fish section of Floating Deep Farms. Obviously structures would need to withstand extreme weather, but offshore wind turbine technology has already addressed these problems.
Eighteen of the word’s megacities, with a combined population of about 350 million and are located along the coastal areas, could use Floating Deep Farms to supply fresh crops instead of using frozen food transported by refrigerated trailers. This will help to reduce expensive carbon miles caused by mass food importation and therefore minimise the world’s overall carbon footprint.
Floating Deep Farms will allow crop production all year round. Up to ten crop cycles per year can be achieved, compared to one to two cycles for conventional agriculture. One small Deep Farm can produce around 80 tonnes of food per annum and crops can be ready for harvesting within three to four weeks of propagation. Floating Deep Farms will have lower energy requirements than traditional vertical farms, with a single Deep Farm having about the same consumption as three UK homes using innovative LED illumination and controls combined with natural lighting using light rods or optical fibres. The carbon dioxide demand of photosynthesising plants can be captured from ambient air using materials such as activated carbon.
Floating Deep Farms can be used to grow a range of vegetable and herb crops including lettuce, kale, spinach, basil, carrots, onions, cucumbers and different types of mushrooms. The crop planting and harvesting could be carried at the top of the Floating Deep Farm using simple belts (or baskets) and pulleys, but robots may also be employed. To harvest the crops the belt with plants would be pulled up, avoiding the manual work required in the shaft.
No comments yet