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I've often wondered what is ecologically better:

  • A tomato from the region grown in a (heated) greenhouse/hothouse
  • A tomato from several thousand km away grown naturally

Ceteris paribus, are there any reliable studies comparing the ecological impact of the two?

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TLDR; a few years ago vegetables grown naturally and then transported by truck over a distance of 1000-1500 km had a lower carbon footprint than vegetables grown locally in heated greenhouses. However due to technical innovations things have changed and the footprint is now equal. Expectations are that in a few years heated greenhouses will have a neutral carbon footprint.


Generally speaking, the production phase of a food makes up the larger part of it's total environmental impact. According to this published Carnegie Mellon University study from 2008

GHG emissions associated with food are dominated by the production phase, contributing 83% of the average U.S. household’s 8.1 t CO 2 e/yr footprint for food consumption. Transportation as a whole represents only 11% of life-cycle GHG emissions, and final delivery from producer to retail contributes only 4%

I'm not sure if similar results also apply to both tomato-scenarios you describe. It probably depends on the exact geographical location, the time of year and the technology used for growing the tomatoes. Nevertheless a while back on a Dutch television program they asked and answered a similar question for 2 types of vegetables. The question was which would be more sustainable in the winter; fresh endive grown locally in a greenhouse, or grown in the ground in Spain (about 1300km from here) and then transport it by truck. According to research they had done the answer was that the endive grown in Spain had a lower CO2 footprint because the local greenhouse requires lots of gas for heating.

However, the same television show also mentioned that fresh green beans which are transported by plane (from Kenia) have a far higher CO2 footprint than the ones transported by boat and/or truck (from Senegal, Marocco or Spain), so the type of transport does make a difference when all else is equal.

Locally grown vegetables that are grown in the summertime, when you don't need a greenhouse, have the lowest CO2 footprint.

For Dutch speakers, here is the fragment about endive and the one about green beans

UPDATE June 2016: Now a few years later, the same television show did an update and again investigated the footprint, this time of tomatoes grown locally in heated greenhouses in The Netherlands versus tomatoes grown outside in Spain or Morocco and then transported by truck to The Netherlands. Due to technical innovations in greenhouses, the carbon footprint is now more or less equal. Dutch greenhouse owners are trying to make their greenhouses CO2-neutral by 2020. Here's the tv fragment (in Dutch).

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    What part of greenhouse growing has such a large carbon footprint? – Laizer Apr 9 '13 at 20:12
  • @Laizer I forgot one important aspect in my answer; I was talking about vegetables that are grown in greenhouses out of season (in the winter) so the large CO2 footprint comes from heating and lighting. In the summer endive and green beans can be grown without a greenhouse. I will edit my answer – THelper Apr 10 '13 at 6:14
  • @THelper - Are you serious? Ocean Tankers and truck transportation creates a huge impact. Local foods avoid that whole thing – Alex S Dec 27 '15 at 7:32
  • @AlexS Transportation of food by aircraft creates an even bigger impact. However if you look at the entire production chain of food, that usually costs much more resources and energy than transportation. But don't take my word for it, read the article I linked too, or the 'Criticism' section of the Wikipedia article on Food miles – THelper Dec 27 '15 at 9:39
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"ecologically" can cover many aspects one of which is the quality of the product...its food value. From my experience in agriculture we know that fast growing grasses (usually using promotants such as nitrogen) do not have the same nutrient value as slower grown grass of the same species. Conversely this must surely apply to vegetables especially in respect to the levels of minerals etc in those vegetables.

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    Welcome to Sustainable Living and thank you for your answer! Do you know if this is something that has been investigated scientifically, that slow growing vegetables contain more nutrients I mean? – THelper Dec 4 '15 at 13:48

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