Because making calories from livestock that grazes on grass is terribly inefficient, which is why we: 1. put them into small boxes usually, which creates a big

Because making calories from livestock that grazes on grass is terribly inefficient, which is why we: 1. put them into small boxes usually, which creates a big nitrogen problem (mixing urine and shit is bad news) 2. feed them other stuff, usually made of soy which is grown in burned down rainforests 3. grow the grass with artificial fertilizers (made out of natural gas) and use pesticides, which also requires gasoline (to power machines) If we're not even talking the CO2e emissions including methane, or the land use, pollution etc then for each calorie of cow you produce you could also create 25 plant based calories. The problem is a lot of people don't want to (only) eat plant based stuff, so we are coming up with ways to manufacture something in a lab that tastes similar to meat. There are several ways to beat the natural process, which is really not that efficient at all and involves a lot of negative effects on the environment even if we disregard animal suffering. I mean, it does make sense if you think about it from first principles: a cow doesn't only turn grass into meat and milk, but also needs to move, to reproduce, it needs to power its brain, etc. We should be able to save a lot of energy in a lab not doing all those things and become vastly more efficient than what the cow does. And we could build a mass production process that is way more easier to manage than cattle and slaughterhouses. That is the theory. The vast, vast majority of meat is grown on land which we can put to better use. The tiny amount of livestock that can be put on a natural rotational grazing system in a sound way making use of land that has no better purpose is so, so small, we shall be eating one burger a year at most from that system.