Modern greenhouses are now in the vanguard of sustainability.
The logic of farmers’ markets begins with this: that the route from harvest to plate ought to be as direct as possible. That’s fine if farmers live round the corner from consumers. But urban land is in short supply, expensive, often polluted, and unsuitable for horticulture. And there is more. Even in a short chain from farm to table, produce can get spoiled. A fresh tomato is not dead; like all fresh products, it’s a living organism with an active metabolism, post-harvesting, that provides a fertile substrate for microorganisms and causes tomatoes to deteriorate very fast. Freshness does not in itself translate into sustainability: unless the supply chain is well?organised, losses can be considerable. And food losses come down to a waste of land, water, energy and chemicals used to produce what is ultimately discarded. This ought to be a good argument for local markets, but it is not. Everything depends on transportation, storage and speed. Poorly packed products go to waste in a matter of hours.
Thanks to decades of research, we now understand the interacting metabolisms of vegetables and microorganisms. We can design high-tech transport and storage techniques that slow down, even halt, deterioration through the use of harmless mixtures of gases. Chips fitted to containers give off signals when the gas composition and temperature need adjusting to plan ripening at the exact moment of delivery. Likewise, to minimise food losses in supermarkets, packaging techniques and materials have been developed to prolong shelf life. Surprising but true: modern treatments with biodegradable plastic bags and sealing create an optimal environment inside the package and reduce loss. So does the industrial washing of packed and cut vegetables, which also saves water, compared with household?level processing.
What then of labour? While ‘handpicked’ sounds attractive to the urban consumer or occasional gardener, this type of manual labour is backbreaking if done all day long. Remuneration is poor, job security close to zero, and only few are willing to do this kind of work. To top it all, the yield from organic farming is low. So think about the alternative: harvesting vegetables such as tomatoes with smart robots that carefully grab each fruit, after assessing its ripeness with a special camera; using smart technology to fine-tune the dosing of fertiliser to every stage of plant development. This enhances flavour and texture, and reduces the overall amount of fertiliser needed. The result is that, in greenhouses, one square metre of tomato plants produces more than 70 kilos of high?quality tomatoes, all of which make it to consumers’ kitchens.
Since we’re on the subject of freshness, consider this: ketchup might actually be better for us than fresh tomatoes – and not just because of economics (the tomatoes used in ketchup are subgrade ones that would otherwise be destroyed). While fresh tomatoes contribute to a healthy diet, human digestive systems are not tuned to extracting most nutrients from fresh tomatoes. Tomatoes are far more nutritious when cooked or processed into ketchup or paste. So, ketchup is no bad thing – unless overloaded with sugar and salt. Indeed, a growing body of evidence suggests that the discovery of fire and cooking – that is, heating food – has been essential in the evolution of the human brain because it allowed for a better absorption of nutrients. Moreover, drying and smoking promoted the preservation of perishable foodstuffs, and perhaps facilitated the emergence of a more complex diet and division of labour.
But surely, you’ll object, tomatoes grown in small-scale gardens taste better. Not so! Double-blind tasting panels have been unable to pick out the greenhouse tomatoes as lacking in flavour, or tomatoes grown without fertiliser as more tasteful. According to Dutch reports on such testing, taste is more dependent on the variety of tomato than on the way it is grown. More importantly, the context of eating determines everything. The on-the-vine tomatoes you consume with mozzarella and olive oil on a village square in Italy will never taste the same at home. It’s a matter of psychology and gastronomy, not chemistry and biology.
In complete contrast to the mantras of organic farming, modern greenhouses are now in the vanguard of sustainability. No longer net?energy absorbers, pilot schemes show that they can produce enough additional energy to heat an entire neighbourhood by storing excess heat from the summer sun in groundwater to be released during winter. Since plants use only a small part of the solar spectrum in photosynthesis, modern technology enables us to find applications for the rest of the spectrum. Greenhouses also utilise residual CO2 from industry to promote plant growth and, in the Netherlands, CO2 from natural?gas production is routinely reused in agriculture. Conceiving greenhouses as net?energy producers opens up new opportunities to build them in hot, arid climates in order to use the stored energy for cooling down the facility.
But energy is just one dimension of sustainable production. Water is equally important. Here too, greenhouses optimise resource use. Under the very best conditions, one kilo of tomatoes can be produced using just 4-6 litres of water, because evaporation from plants can be collected and reused. Meanwhile, according to a 2015 study published in Science Direct, for tomatoes grown in the open air or under open plastic, the production of the same one kilo requires as much as 60 litres of water. Just as water might be reused in greenhouses, pests can be kept out. In a controlled environment, you can minimise the use of pesticides, or opt to use biological controls in the form of predatory insects.
Agricultural science has made great strides in breeding tomatoes with resistance to disease and pests, or with longer shelf-lives and better taste; while the latest genetic and biological techniques have increased our understanding of the genetic diversity of tomatoes and enabled us to speed up the breeding process. Such techniques do not always lead to genetically modified tomatoes. For that to happen, genes from other species would need to be introduced, of the kind that lead to higher vitamin contents in sweet potatoes, for example, or that use bacteria to build resistance against fungi.
So what do we really mean by sustainability? There have been many attempts at providing an exact and measurable definition beyond the statement of the Brundtland Report (1987), which coined the term in the context of equitable development that would not endanger the livelihoods of future generations. The concept originated in 19th-century forestry science to indicate the amount of wood that could be harvested from a forest without damaging future productivity. Since then, it has evolved to mean ‘respecting people, planet and profits’, in the parlance of the UN Earth Summit of 1992 and subsequent Millennium Development Goals.