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

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).