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Comment by circlefavshape | Hacker News Reader

A 155lb human burns 177kcal when walking at 2.5mph[1], so that's 71kcal per mile

There are 340kcal in 100g of wholemeal wheat flour[2], so walking one mile takes around 21g of wheat

Wheat flour creates carbon emissions of 0.80 kg CO₂e/kg [3], so walking one mile creates carbon emissions of 170 g CO₂e

Driving a vehicle powered by gasoline produces tailpipe emissions of around 400g per mile [4]

[1] https://www.healthline.com/health/calories-burned-walking#Wa... [2] https://knowledge4policy.ec.europa.eu/health-promotion-knowl... [3] https://apps.carboncloud.com/climatehub/product-reports/id/9... [4] https://www.epa.gov/greenvehicles/greenhouse-gas-emissions-t...

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However if the calories from your walk come from beef ...

100g of beef gives you 217 kcal [1], so you need 33g of beef for your walk

Carbon cost for beef is 99.48 kg CO₂e/kg [2]

So walking one mile fueled by beef creates ~3.3kg of carbon emissions, over 8 times what would be emitted if you drove

[1] https://www.healthline.com/nutrition/foods/beef#nutrition [2] https://www.statista.com/statistics/1201677/greenhouse-gas-e...

Oh and it turns out the carbon footprint for beef varies significantly by where the beef is raised. Average carbon footprint per 1kg of beef in the EU is 22.1 kg CO₂e [1], so if you're in the EU your beef-fueled 1 mile walk emits ~730g of CO₂e, a little under twice what you'd have emitted if you drove

[1] https://www.thebeefsite.com/news/33676/uk-beef-carbon-footpr...

Except the only people who eat that much beef are certainly not walking anywhere so it’s a fun “statistic” that has no basis in reality.

If I'm reading this right it's not quite apples for apples, as it's comparing the cost to create and move the beef, but doesn't consider the cost to create the car, only the movement of the car.

A car driver could easily eat the same amount of food as a walker, the extra calories would be stored as fat. This also ignores upfront CO2 output from assembling and delivering the car and increased CO2 output from maintaining car infrastructure vs. pedestrian infrastructure. Not to mention numerous other externalities.

Don't forget that the person would be burning calories even if they weren't walking.

The figure for calories consumed when walking is excess calories consumed (compared to sitting still)

Are you sure? It doesn't say that.

I am sure. Think about it for a minute and you'll see why

I don't. Could you explain what you mean?

Here's what I found: the formula given in the article is "calories burned = BMR x METs/24 x hour"

But the METs for lying quietly is 1. The author certainly forgot to subtract 1 from METs in that equation, and could easily have also forgotten to do so when calculating the given numbers.

https://pacompendium.com/inactivity/

It just wouldn't make any sense to tell people "you burn X calories when walking/running/whatever for an hour" if they had to subtract their base metabolic rate from the number.

I agree it should state the excess calories burned. I think the author probably misunderstood the formula.

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