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Comment by jakewins | Hacker News Reader

Some plants have exceptional environmental properties; things like soy, oats (0.1g CO2e/kcal!!) and potatoes. Others are worse than eating meat; if you get your calories from fresh tomatoes (12.22g CO2e/kcal, heated greenhouse) you have an order-of-magnitude higher impact than if you get it from chicken (~1.58g CO2e/kcal, depending on part).

The food system is not easily grouped into "climate-conscious" and "bad"; a vegan diet is better than a western one in every study I've seen, but we could do much, much better.

I highly recommend this study as a starting point, though you need to convert the unit they use, kg CO2e / kg, to the unit we eat in, kcal: https://www.sciencedirect.com/science/article/pii/S095965261...

And, shameless self-promotion: I maintain a food blog that attempts to build an evidence-based low carbon collection of recipes at https://www.carboncook.com

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I mean come on, a diet of 100% tomatoes does not make any sense, right?

The bulk of human calories on a whole food plant based diet comes typically from beans, legumes chickpeas, soy, root vegetables like potatoes and sweet potatoes, starches in general, grains like whole rice, quinoa, etc.

Then another good portion of the calories typically comes from fruit, and another good portion comes from vegetables and salads.

A diet of 100% tomatoes does not make any sense from a nutritional perspective, they are mostly water, but they are a good addition to a balanced whole food plant-based diet.

You're right, it's a poor example. I guess I was thinking of tomato pastas and tomato soups, for instance.

A better one, like you mention, is rice - again a crop with substantially worse carbon impact than chicken.

Fruits are even more complex - if you get them in season, locally and actually eat them, they are fantastic. If you buy them out of season, due to their short shelf-life you'll find they are often air shipped and have outsize waste at the retail level. Avocado is a good example here, water issues aside. In season they have a small impact, out of season they are air-shipped from South America to the rest of the world.

My point being: There are large and non-obvious differences, and they do not clearly align with traditional diets.

Meat is also shipped across the world a lot, like every other food. So the impact of transportation adds up to the impact of production, which is huge.

It's precisely because feeding humans is so resource-intensive that we should not waste so many resources feeding animals.

> A better one, like you mention, is rice - again a crop with substantially worse carbon impact than chicken.

Do you have a source for that? The data at [0] indicates that chicken is about 50% worse than rice in terms of CO2e per Calorie. In fact, chicken is worse than every vegan food listed there except for broccoli, which has very few Calories to begin with.

[0] https://sustainability.stackexchange.com/questions/5883/why-...

AFAIK, the problem with rice is methane not CO2.

That’s accurate. But the data cited in the page I linked is based on CO2 equivalent, which accounts for the higher global warming potential of other gases, including methane. I suspect that the high global warming potential of methane is the main reason that rice is more impactful than the other non-animal-based foods.

Prepared tomato products are not made from greenhouse tomatoes.

They are made from varieties that taste good and they are picked ripe instead of for shipping.

For cooking, canned tomatoes are usually better than fresh store tomatoes. The fresh ones are for salads or whatever.

Nobody really eats tomatoes for the calories though. People (with meat-based or plant-based diets) use tomatoes for flavour and other nutrients.

Tomato pastas like pomodoro and putanesca were my go-to lunches before I learned about this, and tomato soups remain super popular, so I disagree that they are simply a condiment.

Still, perhaps they are a bad general example.

Perhaps a better one would be rice (~2g CO2e/kcal). There the problem is the massive methane emissions produced from the cultivation approach.

Point being: There are huge differences between different foods, and they are non-obvious.

It's precisely because feeding humans is so environmentally impactful that we should not be feeding mostly animals, only to eat them.

The CO2 impact of rice and grains in general can't be compared the impact of animal products, here is a graph - https://i0.wp.com/shrinkthatfootprint.com/wp-content/uploads...

In your examples, the tomatoes were the flavour element you enjoyed, not the main caloric driver. That was the pasta (probably wheat). Your example agrees with the GP.

I really wonder: how is it possible to even consider getting calories from tomatoes? They're tasty, but they will never stop your hunger

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