The "Zero Emission Group," a student association at EPFL Lausanne, has determined the eco-balance of winter lettuce using environmental impact points (UBP).
Fossil energy as a factor
Swiss lettuce from heated greenhouses, which are operated with fossil energy, comes in last place. Its cultivation requires the most energy. Around 90 percent of Swiss greenhouses are still heated in this way in winter. Overall, greenhouses account for about 22 percent of the total direct energy consumption of Swiss agriculture, according to the 2019 agricultural report.
Imported lettuce from Andalusia
The eco-balance of lettuce from a greenhouse in Spain, on the other hand, is significantly better. This is due to the mild climate, explains Curdin Wüthrich of EPFL Lausanne: "The temperatures in Spain allow the greenhouses to operate without heating."
Truck transport does not make a difference
Even the 1800 kilometers by truck from Andalusia to Switzerland do not change the balance in favor of Swiss lettuce. Only when transported by plane is the eco-balance of Swiss lettuce from fossil-fuel-heated greenhouses better. "What we don't take into account are social impacts such as working conditions and the effects of huge agricultural plantations on the landscape," explains Curdin Wüthrich.
More renewable energy for vegetable production
So local doesn't automatically mean greener: unless the greenhouses are powered by renewable energy. In Switzerland, this is only the case for around 10 percent of greenhouses. Options include district heating, wood chips, or heat pumps. Conversion is expensive.
Migros is putting on the pressure
Migros is asking its producers to ensure that 100 percent of Swiss fruit and vegetables come from greenhouses with renewable energy by the end of 2025. An ambitious goal. Coop does not impose any requirements on its suppliers. The vegetable growers themselves have set themselves the goal of heating 80 percent of their greenhouses without fossil fuels by the end of 2030.
Local lettuce without heating is best
Unsurprisingly, locally-grown winter lettuce is the most climate-friendly. Either lettuce can be grown entirely outdoors. These are sugarloaf or lamb's lettuce, for example. Or lettuce that comes from unheated Swiss greenhouses. Michael Moser, vice president of the Vegetable Producers Association of Berne and Fribourg, estimates that unheated greenhouse lettuce accounts for 40 to 50 percent of Swiss winter lettuce.
"Consumers often don't know exactly where the lettuce comes from and how it is grown," criticizes Curdin Wüthrich. This should change because only those who are informed can buy consciously.
Source: SRF