Growing vegetables in greenhouses can be done very efficiently. The Wageningen University researched high-tech greenhouses in Riyad (Saudi Arabia) and found tha

Growing vegetables in greenhouses can be done very efficiently. The Wageningen University researched high-tech greenhouses in Riyad (Saudi Arabia) and found that it only required 5 liter fresh water per kg tomatoes, compared to 168 liters in a low-tech greenhouse [1]. This is possible using a closed system that recycles the water that evaporates in the greenhouse. The low-tech example is a plastic tunnel without such facilities (the most commonly used type of Greenhouse in the Middle East). The yield per square meter was also 50% higher for the high-tech greenhouse compared to the low-tech greenhouse. [1] https://www.wur.nl/nl/nieuws/Nieuwe-onderzoekskas-in-Riyad-maakt-30-90-waterbesparing-mogelijk.htm https://www.wur.nl/nl/nieuws/Nieuwe-onderzoekskas-in-Riyad-m... (in Dutch only)