One way to look at it is to compare it with the EV debate- the carbon expenditure to create a new EV far outweighs the net emissions of keeping an old combustion vehicle running for a year. But say you drive 20,000 miles a year. At some point (I forget the math but it’s 5-10 years) you’ve closed the gap and now you’ve got a real net deduction of emissions per year (vs driving the ICE). It’s gonna be a lot more variable with humans and the types of food we eat but there should be a similar crossover point there too.