I'd be interested in knowing what the CO2 emissions were from these. You still need to feed the yeast, so you'll have the CO2 emissions involved in growing a crop associated with this. And if you look at the chart in the OP, you'll see that grain production is about half the CO2 emissions of milk. That's likely part of the milk CO2 production accounting.
In addition, you'll need more cleaning/sterilization/mixing. I'd guess that it's lower, but I wonder how much lower.
And then there's the other products that generally get thrown into the mix to make up for things like missing fats. For example, a vegan cheese based on bacteria will often include coconut oil, probably to get the same fat profile.
Whey is an interesting product in general because it's a waste product of cheese making.
Feed efficiency is critical when doing these calculations as cows inherently need energy to survive not just produce milk. As such even if you use the same crop two different sources of protein can have wildly different levels of CO2 emissions embedded in their creation. https://en.wikipedia.org/wiki/Feed_conversion_ratio
I think it is likely more efficient. That said, cows do have the advantage that the food they consume needs little to no processing in order to produce milk. The yeast needs pretty precise processing of the incoming mash both to make sure a wild yeast strain doesn't make it's way in, and to make sure the yeast ultimately produces the right proteins.
You can't just throw in grass clippings into a vat and get whey. You can throw grass clippings into a cow to get milk (though, TBF, I dislike grassy milk).
I agree it’s likely to be more labor intensive per lb of feedstock, but only 21% of calories in milk are protein and overall milk has ~10% of the initial energy. So you’re looking at ~2% of the energy from these crops ending up as milk protein.
That’s a lot of room for improvement which then means far less labor on growing crops.
Cows are pretty terrible because of methane from their burps (not farts; burps). People are working on that but it's still real. A 50% drop would be very significant
In addition, you'll need more cleaning/sterilization/mixing. I'd guess that it's lower, but I wonder how much lower.
And then there's the other products that generally get thrown into the mix to make up for things like missing fats. For example, a vegan cheese based on bacteria will often include coconut oil, probably to get the same fat profile.
Whey is an interesting product in general because it's a waste product of cheese making.