Since we first planted seeds in the earth with the intention to feed ourselves from the plants they produce, we’ve sought out ways to improve how we grow and harvest crops. Today, agricultural practices are a world apart from their beginnings. And yet, amidst the industrialisation of agriculture the principal ambition remains the same — to produce a large, nutrient rich harvest.
In modern times, new concepts have entered into agricultural (and horticultural*) practices. In parallel to seeking to optimise crops, we now think largely in terms of how we may operate agriculture more efficiently. We work towards energy and cost efficiency, sustainability and lowering inputs, be them labour, maintenance, or material ones.
Science has of course dramatically impacted conventional agriculture: rain can be supplemented with irrigation, soils enhanced with fertilisers, and plants supported with pesticides. While these tools have left agricultural practices more productive, in many cases they’re far from ideal considering their costs on the environment.
In a bid to assure the societies with more sustainable agricultural systems, we’re increasingly looking to innovation in science and technologies as a means of securing harvests.
The technologies presented in this article, focussing on hydroponics and smart lighting systems, are already widely practised but they’re also subject to massive amounts of research and innovation. The outcomes of these efforts provide a glimpse into how future agricultural systems are likely to look.
*The word ‘agriculture’ has Latin origins, stemming from ‘agri’ (field) and ‘cultura’ (cultivation); whereas ‘horticulture’ stems from ‘hortus’ (garden). In practice they deal with much the same issues, differing mostly in context and scale. In many instances, horticulture is taken to refer to greenhouse growth.
The Challenges of Food Security
A critical backdrop to agricultural innovation is the fact that we face unprecedented challenges in global food security. Today, the World Food Programme estimate some 795 million persons suffer from daily hunger and under-nourishment.
As the world’s population grows, arable land continues to decline. Data presented at COP21 last year showed that around one third of the world’s total arable land has been lost in the last 40 years (Cameron et al., 2015). In part, this loss is through consequences of climate change, including droughts, floods and water scarcity. But loss of arable land is also an unintended consequence of conventional agriculture.
Often described as intensive agriculture for the high level of inputs utilised to increase yields, it is an undoubtable truth that conventional agriculture carries significant, dire consequences for the Earth. Its practices — reliant upon fertilisers, pesticides, and massive amounts of irrigation — are already leading to massive and widespread disruption of natural ecosystems (see, Anderson & Gugerty, 2010). If left unchecked, the damage can be irreversible.
During preparation of this article, a report published in the Lancet provides additional insights on the consequences of climate change for global food production: concluding that climate change may kill 500,000 adults in 2050 as a result of changes in diet and bodyweight due to reduced crop productivity (Springmann et al., 2016).
So while we wrestle with the fact that more persons face daily hunger than populations of the European Union and North America combined, we’re aware that conventional agriculture is not the solution. Indeed the hope of food security for the world’s population — which is widely acknowledged as an attainable goal –, goes hand in hand with agricultural solutions which are more sustainable for the planet.
Leaving these topics aside, there is an entirely alternative route to food production that already provides a significant amount of our food, and holds even greater potential for the future. Ironically enough, it involves turning away from the Sun and soil — the very foundations of conventional agriculture for millennia.
A side-note: this article could very well have been written without this note on food security and hunger. Phlebas is first and foremost a site considering consequential technologies. But after consideration, the notion of a consequential technology rests upon recognition of for whom, and to what end, a technology is consequential. In the present case, the context underlines the significance of sustainable agricultural solutions: what could be more consequential than solutions which bring about a world in which all have enough to live full and healthy lives?
For more insights on food security and world hunger, see The State of Food Insecurity in the World, 2015, from the World Food Programme.
Hydroponics involves the cultivation of plants in the absence of soil. Although we tend to think of nutrient-rich soil as key to successful growth of plants — be it a house plant or an entire fields of crops —, soil itself is irrelevant to a plant’s growth. It’s the nutrients held within the soil which are key. Soil is important only in so far as it acts as a medium that holds nutrients and water; making them available to a plant’s roots.
As it turns out, ditching the soil actually opens up multiple avenues for improved control and efficiency in plant growth, and at the same time makes it possible to grow plants under all sorts of circumstances and conditions not possible in the natural world. In theory, and provided the right set-up, any plant or crop could be grown hydroponically. To date, the list of crops commercially grown hydroponically is somewhat limited to leafy greens like lettuces, and herbs; but there are reasons for this that we’ll get to.
Of course plants still require nutrients and water. Regarding nutrients, there are the essential chemicals, including: nitrogen, phosphorous, potassium, calcium, magnesium, and sulphur; then there’s other so-called ‘micronutrients’ also required for plant growth, but in far smaller quantities. In hydroponics, all these are provided in the form of nutrient solutions, which can be tailored to provide plants with the precise balance of nutrients and water they require.
Hydroponic systems come in many forms; but at least one important level over which systems can be distinguished is where plants’ roots are located.
In ‘liquid culture’ systems, roots hang into a nutrient solution, where the solution is either a liquid (pictured above). A similar practice is aeroponics — where the nutrient solution is a mist.
In an ‘aggregate culture’ system, roots grow into an inert medium (for instance, sand, gravel, Rockwool, or foam) which is then irrigated with a nutrient solution.
All told, multiple advantages stem from hydroponics.
Firstly, without soil, there’s no need for chemical treatments commonly used to protect against harmful bacteria. In fact, as will be discussed, the high level of control over environmental conditions in hydroponic systems means plants can be cultured to an exceptionally healthy and organic level.
Hydroponics also eliminates pressures and damaging effects that intensive agriculture has on the Earth, including soil degradation, erosion, and pollution of natural sources of water (for more insights, see Food and Agricultural Organisation, UN).
An important characteristic of hydroponics is that it’s suited to high planting densities — meaning a large number of plants can be grown in close proximity to one another. Moreover, hydroponic growth-beds can be built with a so-called vertical farming design. These attributes mean that space is used efficiently and contribute greatly to the high yield per unit of land that hydroponics can achieve; something described in greater detail below.
Another significant advantage of hydroponics is the control it provides over watering. Physically, plants still require the same amount of water to grow, but watering can be undertaken in a very precise fashion: the right amount, at the right time, without waste. This is in stark contrast to field irrigation which incurs tremendous amounts of wasted water since anything not used by plants, percolates down through the ground and away. Hydroponic systems are often closed-loop; meaning that very little water, if not none at all, is simply lost. Even evaporated water can be captured, and recycled.
At its most basic level, hydroponics is a simple affair. So much so that it’s easily undertaken by individuals in their homes and gardens. However, the notion of hacking nature with hydroponics — growing plants not in their native soil, but in alternate systems — is taken to an altogether more sophisticated level when it’s coupled with greenhouses growing produce at commercial scales.
Greenhouse agriculture is considered to be part of a sustainable solution to meeting food demand — even without introducing hydroponic systems to them. In large part because they limit the damaging consequences of intensive agriculture.
Because of the enclosed nature of the greenhouse, we can control for the unintended consequences of fertilisers, and other chemicals that may still be utilised. Additionally, irrigation can be provided in a more precise, sustainable manner, than in field irrigation; optimised to particular needs of plants and their growth cycles.
Additionally, inherent to greenhouses is a level of control not achievable through conventional means of agriculture. In principle, greenhouses allow for almost total control over environmental conditions. Sunlight can be supplemented with artificial lighting to extend and promote plant growth; soil conditions, pH levels, nutrient content and so on, can all be monitored and readily adjusted. As a result of these advantages, greenhouses produce larger harvests (or yields) per unit of land than conventional field farming.
Greenhouses can be situated on non-arable land — land that cannot be farmed due to say contamination, or soil conditions or the climate and weather. And, lastly, it goes without saying, but greenhouses can support growth of crops in countries which by rights aren’t capable of supporting those crops naturally.
The coupling of hydroponics and greenhouses was a foregone conclusion — adding all the advantages of hydroponic’s control and efficiency into the greenhouse system. A system that could be built anywhere in the world, regardless of climate or landscape, to grow any fruit or crop. But how efficient are hydroponic greenhouse systems, and how do they compare to conventional agriculture?
Insights on the efficiency of hydroponic greenhouses can be found in a recent study (Barbosa et al., 2015) in which researchers conducted a comparison of conventional field-based agriculture versus commercial scale hydroponic greenhouse production. The analysis considered the land, water and energy requirements of the two techniques.
The crop under study was lettuce. This is notable because it’s the case that Arizona — where the conventional agriculture data was drawn from — happens to be especially efficient in their growth of lettuce…meaning that the data set represented something of an ideal, best-case scenario.
The analysis revealed several things. Firstly, that greenhouses produced a yield some 11 times greater than field grown lettuce (41 kg/m2/year and 3.9 kg/m2/year respectively). Greenhouses also carried far lower water demands (20 litres/kg/year) than fields (250 litres/kg/year).
Importantly though, energy demands were far higher in greenhouses than in field agriculture: 90,000 kJ/kg/year compared to 1100 kJ/kg/year. Important to note on this matter is that the study calculated energy demands of greenhouses featuring supplemental lighting using traditional high pressure sodium bulbs.
That point about lighting aside for the moment, the authors did point out that, “most of the energy use for the hypothetical hydroponic greenhouse can be attributed to the heating and cooling loads. This is primarily due to the fact that the greenhouse was sited in Yuma, Arizona, an area which can have average temperatures of 34.7°C in the summer and 14.1°C in the winter,”. For this reason, the authors concluded that “the feasibility of hydroponic systems is heavily reliant on the climate of farming locations,”.
Overall, the report provides stark evidence for the increased yields and water savings achieved through hydroponic greenhouse farming — something demonstrated many times before.
Of course the issue of increased energy use in greenhouses cannot be ignored, as it undermines the notion that hydroponic greenhouses provide a sustainable solution. If hydroponics is to become a major source of world food production, the issue of energy use must be addressed.
Fortunately, this very issue is not lost on the scientific and sustainable thinkers of the world — something discussed in the next section as we consider the increasing sophistication of hydroponics, and the application of new smart technologies.