The rough number is that apparently 10% of CO2 equivalent comes from meat farming, but don’t trust this.
What did surprise me though is that a much larger benefit would result from repurposing the feed stock and grazing land, together comprising ~25% of the earths habitable land. Land and ecosystem restoration would likely result in feedback loops in the opposite direction.
I have a friend in Denmark that used to run a small carbon neutral farm, where the carbon offsets were all generated by other activities on his land. His all in cost for a kilo of pork was 700kr, or over $100 dollars. Meanwhile, you can but a kilo of port at a supermarket for ~$20. He could only sustain this because he ran a farm restaurant selling the best burgers in town, and even these were probably a loss leader for his best-in-town fries and mayonnaise making up the difference.