I spent a fair bit of my career doing something called lifecycle analysis, which is a method to assess and compare the environmental consequences of various processes. To explain, let’s suppose one is interested in energy use and greenhouse gas production. If one simply evaluates the energy used by and emissions from Factory #1 and then again for Factory #2 and compared them, the results would be meaningless. This is so because both require raw materials and those materials must themselves be produced. Also, the type of energy matters. So, if Factory #1 uses half the energy (total joules) as #2, but it is electricity rather than natural gas, it isn’t doing any better and may be doing worse than #2 because we need to combust about 2-3 joules of gas to make a joule of electricity.
If you want to worry about glues, you will need a careful analysis of the upstream portions and will likely need to know about embodied emissions associated with plant construction and end of life emissions from disposal. This is really, really hard to get right, especially for industrial chemical processes because of how often unrelated chemicals and products are co-produced or share energy through process heat integration.
Moreover, need to consider many aspects here. Energy use and GHGs is just one thing, but eutrophication, criteria pollutants, and a hoard of other emissions and environmental changes are possible.
In the present context, the energy use and petroleum consumption for the production of chemicals to make PVA glues sounds bad, as perhaps might the disposal of “plastic,” but hide glue will be associated with animal husbandry which inevitably is associated with methane emissions, one of our big challenges. Animal husbandry couples to farming, which is a large driver for fertilizers and chemicals. Using hide glue likely is associated with plastic consumption upstream, but I have no idea how much.
I applaud your diligence and concern. We all should make choices in our personal behaviors rather than waiting for some global or governmental solution. Unfortunately, there are times when it is just too hard to know which thing to choose! People like me aren’t doing their jobs to get the required info. But another way to look at this is that using wood glues for woodworking and maybe even for all industrial operations, is quite likely to be a small effect compared to plastics use in the food industry, packaging industry, and so forth.
I use hide glue, but not for environmental reasons. I use it for woodworking reasons.
Hope this wasn’t too long, too far afield, or (most likely) way too boring. Again, I applaud your considerations, but suspect you shouldn’t drive yourself nuts over it. Probably the most important choice is to use a method that reduces waste of whatever you choose including waste associated with product lifetime.