AbstractReducing motorized transport and increasing active transport (i.e. transport by walking, cycling and other active modes) may reduce greenhouse gas (GHG) emissions and improve health. But, active modes of transport are not zero emitters. We aimed to quantify GHG emissions from food production required to fuel extra physical activity for walking and cycling. We estimate the emissions (in kgCO2e) per kilometre travelled for walking and cycling from energy intake required to compensate for increased energy expenditure, and data on food-related GHG emissions. We assume that persons who shift from passive modes of transport (e.g. driving) have increased energy expenditure that may be compensated with increased food consumption. The GHG emissions associated with food intake required to fuel a kilometre of walking range between 0.05 kgCO2e/km in the least economically developed countries to 0.26 kgCO2e/km in the most economically developed countries. Emissions for cycling are approximately half those of walking. Emissions from food required for walking and cycling are not negligible in economically developed countries which have high dietary-related emissions. There is high uncertainty about the actual emissions associated with walking and cycling, and high variability based on country economic development. Our study highlights the need to consider emissions from other sectors when estimating net-emissions impacts from transport interventions.
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- The walking thing you can mostly calculate yourself if you only examine particular foods, but here's some study looking at the dietary impact in practice averaged across a country (walking has comparable emissions to a 22mpg car trip in developed countries) [0].
- For cotton reusable bags (very common for all sorts of reasons; all my reusable bags are cotton and not because of any particular intentional selection), you need 50+ trips to the store to hit a break-even point [1] in greenhouse emissions. Similarly with the 50x thicker plastic bags stores in CA sell compared to disposable shopping bags. That's 1-2yrs for the break-even point with weekly or biweekly shopping…
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trips, worse if your usage distribution is temporally nonuniform (e.g., owning 5 bags but sometimes only using only 1-3 for slightly more frequent shopping trips and occasionally using all 5). Properly reusable bags are likely worth it, but it's not an immediate or obvious win unless you use them regularly and they're sturdy enough to not wear out too quickly (enough material is involved and the timescales are long enough that you should also consider the impact of the disposal method and a number of other things).
- Some of the other points like linearity in the number of days between shopping trips should be obvious. I'll leave investigating everything else as an exercise for the reader.
[0] https://www.nature.com/articles/s41598-020-66170-y
[1] Not "source" so much as a summary of sources, so I referenced the smallest number in the article to give the argument more weight: https://www.cnn.com/2023/03/13/world/reusable-grocery-bags-c...
I think you may be thinking of the question, "how much greenhouse gas does it take to move a human X miles if they are self-powered versus using an ICE?"
For example this study https://www.nature.com/articles/s41598-020-66170-y.
> our estimates suggest that the net emissions associated with the ‘fuel’ required for driving, walking, and cycling may be comparable in some settings
With the caveat that they're looking at *per-mile* emissions, and nobody in the developed world is walking 60 miles to and from work every day.
However there's an important clarification to your recollection.
- You're correct that eating meat (and dairy) is very carbon-intensive.
- You're not…
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correct that agricultural transportation is significant. It doesn't even make it into the paper above, as far as I could find. Agricultural transportation, even things like flying blueberries to California from Chile, is negligible compared to the carbon cost of food.
You can see that in the following graph. Red is transport. You have to look closely even to see it. https://ourworldindata.org/food-choice-vs-eating-local
A car is more or less efficient than cycling, depending on the food, car and source of electrical power, and manufacturing CO2 production. The bicycle production emits a less CO2 than the car production, tilting the comparison at the beginning of the lifecycle of both.
The GHG emissions associated with food intake required to fuel a kilometre of walking range between 0.05 kgCO2e/km in the least economically developed countries to 0.26 kgCO2e/km in the most economically developed countries.
A Tesla model 3 according to WLTP test cycle uses
0.191 kWh / km * 0.434 kgCO2e/kWh = 0.083 kgCO2e / km
Sources
https://www.nature.com/articles/s41598-020-66170-y https://www.tesla.com/de_DE/support/european-union-energy-la... https://www.umweltbundesamt.de/themen/co2-emissionen-pro-kil...
Joon Sung Park, Joseph C. O'Brien, Carrie J. Cai +3
Believable proxies of human behavior can empower interactive applications ranging from immersive environments to rehearsal spaces for interpersonal communication to prototyping tools.
(The third edition corrects minor typos and adds 3 chapters synthesized from published papers plus an appendix on maximum entropy distributions.) The monograph investigates the misapplication of conventional statistical techniques to fat tailed distributions and looks for remedies, when possible.
We analyze the storage and recall of factual associations in autoregressive transformer language models, finding evidence that these associations correspond to localized, directly-editable computations.