Otherwise: A nice website!
(Not associated with the brand or with any vendors, it's just the brand I've been buying.)
For example, the protein concentrates from whey or milk are obtained by just two filtrations through filters with different pore sizes, the first coarse filter retains any larger particles, including bacteria, while the second fine filter retains the protein particles and passes the water with lactose and fat and also with any contaminants that are soluble in fat or in water.
Thus the protein concentrates from whey or milk normally have less contaminants than in the whey or milk used for their production.
In a suitable hermetic packaging, e.g. in a metallized plastic bag, protein powders may be stored for years without refrigeration, which I find extremely convenient and I consider as one of their important advantages over other protein sources, such as meat or dairy, together with the advantage that the protein powders require much less storage space and they are much lighter, being composed of almost pure protein.
The latter advantage, in volume and mass, is also an advantage over the vegetable sources of proteins, e.g. dry legumes or wheat flour, which can be stored for a long time, but which contain much more starch than proteins.
Even then, unless it is recycled aluminum, I'm not sure how much you're gaining, environmentally. Heavier to move, harder to form, probably covered in some sort of coating on the inside anyway. Plastic isn't great- pretty much everything except weight, water impermiability and ease of forming are downsides, but metal isn't free either.