Did you know that our diet is responsible for one third of the damage to nature, caused by every consumer each year? It is even ahead of mobility with car journeys and holiday flights. We know that animal products or products from overseas pollute our environment. When it comes to overseas products, however, we often only think of avocados or mangos but there is another fruit, which should be considered: the tomato. I was surprised when I heard that the tomatoes we use for a good Italian pasta sauce do not necessarily come from Italy, Spain or France. China, for example, is one of the largest producers of industrial tomatoes and tomato puree. They deliver 1000 tons of tomato puree per week to Italy. How come? The demand for tomatoes, tomato sauces and purees is high all year round. In Switzerland, Tomatoes are the most popular vegetable after carrots with 6.93kg per capita consumption in 2016. If the consumption of sauces would be included as well, it would certainly be more because 1 kg of tomato sauce needs 6 kg of fresh tomatoes. In the supermarket, tomatoes are offered throughout the whole year despite the fact that they are only in season from July to October. To meet this demand, tomatoes in Switzerland are produced in greenhouses or imported from abroad. California is the leading producer (followed by China and Italy) -approximately 96% of total US tomato production and 31% of total global tomato production is located there.
We often believe that greenhouse tomatoes from Switzerland are more sustainable than tomatoes from China/California or vice versa. Therefore, I asked myself which option is the most sustainable or is there even a sustainable choice? Transport requires diesel-oil and greenhouses requires heating-oil. In a study of the University of British Columbia, they compared local greenhouse-grown tomatoes to Florida field-grown tomatoes. The two methods of tomato harvesting were compared based on the global warming potential and human toxicity potential. The pictures show the quantities of CO2 emissions produced per kilogram of tomatoes in each production process, once with transport and once without transport to the same end consumer. The result shows that the physical process of producing field tomatoes in Florida has a lower global warming impact than the process of producing tomatoes in local greenhouses. However, if transport is added, greenhouse tomatoes have a lower global warming potential.
The situation is similar with the human toxicity index. Local greenhouse tomatoes have a lower impact on human health than Florida tomatoes mainly due to the emissions of the transportation phase of the Florida tomato to the market.
Due to the continuously improved heating and insulation technology in the greenhouses, natural gas consumption has been reduced by approximately 50%. Also, greenhouses use less water and the water collection technology eliminates the effects of water pollution.
It can be assumed that vegetables grown in local greenhouses are more sustainable than vegetables, which were harvested in Florida. To mention is also the significant social and economic impact of buying locally grown products, even if they are more expensive. Buying locally also means supporting fair labour practices and working conditions. Due to the price war of the competitors, there are even larger producers who want the big profit and do not care about working conditions. In China, for example, the working conditions for field workers are unfair; they earn 0.01 Euro per kilo. China is currently expanding into Africa, where employees are paid even less. The regional market collapses under the pressure of cheap imports. Farmers in Africa cannot keep up with the low prices of the big Chinese companies. Such situations lead to poverty and misery. Economic refugees are not accepted in Europe, even though our consumption and eating habits are to some extent responsible for poverty in Africa.
Anyway, it is not only important to buy local but also to buy seasonal organically grown products because even greenhouse tomato production requires high amounts of fossil fuel (water, oil, nitrogen fertilizer etc.) as it can be seen in the graph.
In addition, greenhouses require huge areas and not all are equipped with the latest technologies.
Unfortunately, I have never managed to buy only seasonal and regional fruit and vegetables. Sometimes I just didn’t know which product was more sustainable. I will certainly pay more attention to the origin of my products. Thanks to my seasonal calendar, I know that there are plenty of tasty vegetables in winter available. Here some tips: various types of cabbage, root vegetables such as parsnips, beetroot or Jerusalem artichoke, leek, lamb’s lettuce and mushrooms are in season in winter. Carrots, potatoes and pumpkins are usually left over from autumn. Bon appétit!
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Der Verband Schweizer Gemüseproduzenten, 2017. Medien. Online: http://www.gemuese.ch/Meta/Medien/News/Schweizer-Tomaten-haben-eine-gute-Umweltbilanz (17.11.2018)
Kelly, J., Macdonald, A. & Wilkes T. Life Cycle Analysis of Tomato Production. Comparing British Columbia Greenhouse-Grown Tomatoes to Florida Field Grown Tomatoes for use at the University of British Columbia. Report, Vancouver: The University of British Columbia. Online: https://open.library.ubc.ca/cIRcle/collections/undergraduateresearch/18861/items/1.0077988 (21.11.2018)
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Pydynkowski, K. et al., A Life Cycle Analysis for Tomatoes in NH, Dartmouth: College in Hanover, New Hampshire. Online: http://asi.ucdavis.edu/UCDProcessingTomatoLifeCycleAssessmentReport_8March2018.pdf (15.11.2018)
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Utopia, 2015. Bio. Online: https://utopia.de/0/magazin/richtig-regional-saisonal-ernaehren-im-winter (17.11.2018)