By Jerry Frenkil
Tomatoes are the star of summer produce, at least in my house. We grow some of our own cherries (Sungold100 is our favorite) and we also frequent the great local farms for these delicious fruits.
On Concord’s Ag Day on September 9, we’ll celebrate the quantity and especially the quality of local produce. We should also be celebrating their energy efficiency.
All plants require energy to grow, and it’s interesting to consider the energy required to grow, say, a tomato. It turns out just such an analysis was published by Vaclav Smil in IEEE Spectrum as The Tomato’s Energy Footprint (https://spectrum.ieee.org/how-much-energy-does-it-take-to-grow-a-tomato).
In his analysis he compared the energy efficiency of locally grown field tomatoes to those grown in greenhouses. It’s no surprise that the greenhouse raised tomatoes require more energy, but the fascinating part is just how much more.
Growing tomatoes requires direct energy in electricity, gasoline and diesel fuel, not including sunlight. Indirect energy is also needed in the production of fertilizer, pesticides and fungicides. But tomatoes don’t just consume energy; they also produce it (or more correctly, they transform and store it).
You can think of a tomato’s energy efficiency as a ratio of energy stored to energy consumed – the energy contained by a tomato divided by the energy required to produce it. A modest-sized field tomato, weighing about four ounces, contains about 22kcal of edible food energy, which turns out to be about the amount of energy required to grow it, not including sunlight. This can be thought of as a 1:1 tomato: one part of input energy results in one part stored energy.
Smil’s analysis showed that store-bought tomatoes, often grown in greenhouses in other states and countries, require much more energy to produce. Heating costs are substantial, as are storage and trucking costs. These additional costs result in energy efficiencies ranging from 1:21 to 1:150; that is, such a store-bought, greenhouse-produced tomato requires 21 to 150 times more energy to produce than is “created.”
I find this difference between field tomatoes and greenhouse tomatoes to be astonishing — not to mention that greenhouse tomatoes often disappoint in flavor as well as in energy efficiency.
But here in Concord, we have a wealth of field tomatoes available to us, at least at this time of year. Our tomatoes are fresh and delicious and energy efficient too. Ag Day is a great opportunity to celebrate our farmers and thank them for growing produce that tastes great and is more sustainable. Supporting local agriculture can help reduce climate warming emissions. You can also learn more about meaningful ways to reduce your climate impact by visiting Concord’s Climate Action Committee table during Ag Day in Concord Center. And while there, don’t forget to try some of those sweet, juicy, energy-efficient tomatoes!