Honestly, I don’t trust the source. What an animal science professor says off the cuff in an interview is something that should be verified with real data.
The question relies on how much carbon ends up in CO2, CH4, and fixed in the soil between use of what would become cattle feed. Carbon is conserved without a doubt, but how much ends up as gas and which gas is important.
Carbon dioxide doesn’t matter because every bit which ends up in the air had to be taken from the air a short time before to build plant matter. Methane matters because it is a much more potent greenhouse gas and how much gets as methane instead of carbon dioxide makes a difference.
The question relies on how much carbon ends up in CO2, CH4, and fixed in the soil between use of what would become cattle feed. Carbon is conserved without a doubt, but how much ends up as gas and which gas is important.
Carbon dioxide doesn’t matter because every bit which ends up in the air had to be taken from the air a short time before to build plant matter. Methane matters because it is a much more potent greenhouse gas and how much gets as methane instead of carbon dioxide makes a difference.