Almost quit beef due to the info in Cowspiracy in which I believe they pointed out that if everyone were to switch to grass fed beef there would literally not be enough grassland to support it (this is probably true, with the assumption that various plant crops continue their unsustainable land footprint). However, having seen also "The Magic Pill" on Netflix, I've concluded the optimal solution is probably more, healthier beef, and less plant agriculture land. The real problem isn't the cows, it's what the cows eat, which is mostly corn, soy, grains etc. Put as simply as I can: if humans committed to eating fewer carbs, and eating grass fed fatty meat and high quality plant oils for the bulk of their calories, the resulting system would produce huge carbon capture because grassland in its 'growth phase' is a very efficient carbon sink, and is more supportive of healthy soil than fields of corn, soy, and grains.

So you chose to keep eating beef, because you think it's possible to create sustainable beef, even though the beef you do eat is not sustainably sourced?

How is it possible to product carbon capture, if all the grass is being consumed by cattle who then either exhale it or get eaten by humans who exhale it?

I understand the skepticism. I actually try to eat grassfed beef where budgetary constraints allow. In my opinion, grassfed beef today is the most sustainable land -based option given that the person consuming it is fat adapted. If eaten it in the traditional American diet of steak, potatoes, often beer, and bread, the result of this is a less efficient metabolism, the net result of which is more unsustainable agriculture because the person is going back to relying in part on intensive plant agriculture. I have an answer to the exhalation question, which I think is important to understand. The hydrocarbons generated by photosynthesis in the grass go into the cow, become protein and fat in the cow, and then go into the human, and become a hydrocarbon based store of energy. Most of the result of the use of this store is energy, heat, and two biproducts (H2O and CO2) (the efficiency ratios here matter and they are favorable in both healthy cows and humans). As long as we have a human/animal population on earth, we will have a system that produces energy (muscle movement and neurons firing), heat (waste from the inefficiency of our neuro-muscular-skeletal system) and CO2 and H20. The question, which I think grassfed beef addresses, is what is the most efficient way to take sunlight, water, and CO2, and convert that into energy for the human/animal population to use? To this I'd add in my optimal system we actually address the dual-threat type problems of overfishing and ocean acidification, and encourage sustainable harvesting of smaller fish with population management controls (ie sardines and anchovies).

The economics of veggie proselytism actually look pretty good.

Animal Charity Evaluators found that for every $11 spent in online ads, you could make one person go to a website, sign up with their email, and pledge to go vegetarian for a year. The average vegetarian [1] produces 1.5 metric tons less CO2eq per year, so this means that the online ads decrease carbon at a cost of $7.40 per ton. That's cheaper than buying typical carbon offset certificates ($10-$15 per ton).

Maybe it's too optimistic to assume that everyone who makes a pledge on the website actually stays vegetarian for a year, or that they were average-level meat consumers before. Still, animal farming is bad enough that reducing it is probably cost-competitive with other current CO2 reduction approaches.

[1] I'm not sure if their use of "vegetarian" means "completely vegan".

It is too optimistic to assume that anyone who makes a pledge on a website follows through on it for even one day.

It's the online equivalent to honking your horn for the protesters holding up signs next to the road. Easily done; easily forgotten.

I don't understand your math.

Wouldn't you need to look at the difference in CO2eq between an average non-vegetarian and vegetarian?

Sorry, typo – I meant to say less than. Fixed.

I think the real problem would be induced demand from cheaper prices of meat making up the difference.