Yeast is not an animal, nor a plant. It's a single-cell fungus.
It's about 3 micrometers in diameter. 8 times smaller than human hair.
If Yeast has access to oxygen (aerobic respiration), it produces: Carbon Dioxide + Water
When Yeast has no oxygen (anaerobic respiration), it produces: Carbon Dioxide + Ethanol
For Alcoholic Beverages (Wine, Beer, Spirits) Yeast is left in bottles or kegs with no oxygen so it produces ethanol (alcohol)
For Baking (Bread, Cakes) Yeast is mixed in the batter and has access to oxygen. It produces gas bubbles and some water.
For Nutritional Yeast Nutritional Yeast is inactivated yeast - dead cells.
Active Dry Yeast Active Dry Yeast is made of dehydrated cells, dormant. They reactivate in water. Active Dry Yeast stores for longer.
Instant Yeast Active Instant Yeast is a type of dry yeast with smaller granules, making it faster to activate.
Fresh Yeast Fresh Yeast is live blocks of yeast. It doesn't need to be reactivated but it stores for only about a week.
Yeast is 100% Vegan!
Manufacturing is relatively sustainable. It produces low levels of byproducts.
Yeast is not produced from or with animals.