Selvin, producing plasterboard is energy intensive (having visited several production sites in a previous professional capacity). Whether or not manufacturers have improved their processes to be more energy efficient is probably something you would have to ask them directly.
As for recycling, well in France, at least, you can take your old boards to the public dump and they generally have a separate container set aside for people to leave their used plasterboard in. Whether or not, and how, this actually gets recycled does not appear to be easily accessible information.
Plasterboard’s main component is, after all, gypsum, which requires a lot of energy to undo the very strong bonds that form on crystallisation out of the slurry from which it is made. Recycling the cardboard coatings (if at all possible) that form the board outer surfaces also requires significant energy input. Other components go into the manufacture of plasterboard, including a whole range of not so very environmentally friendly additives (retardateurs de prise, accélérateurs de prise, agents thixotropes, dispersants, azurants, agents blanchissants, colorants, renforts, fibres, etc), which I doubt can be separated out or disposed of very easily.