There is specialized plastids that can use solar energy to turn co2 into a high resistant carbon based composite material that can be used to replace steel and concrete in construction. This composite is also an nicer and more durable alternative to all kind of plastics.
The process is called photosynthesis and the material is commonly known as "wood".
Replacing cows with yeasts that produce whey and casein (the 2 proteins in milk) is already underway. That could go along way to reducing methane and carbon dioxide.
Imagindairy's milk and cheese products will actually be much healthier than milk that comes from animals, since it will not contain cholesterol, lactose, or somatic cells.
Oh ffs. Blood cholesterol is a red herring, more or less of the "dead fire fighters found at conflagration, let's blame them for it" type, additionally nutritional cholesterol has no impact on blood cholesterol. Lactose well your gut might not care for it but mine is totally fine with it and it's a sugar, it contributes massively to taste and aroma -- most lactose-free milk is produced by "pre-digesting" it by adding lactase making it sweeter as broken up lactose, glucose+galactose are, well, sweeter. If you just use saccharose instead or such you won't get actual milk taste. Not having random cow cells in there well why not if nothing else it's going to make things more shelf-stable.