Plasterboard as source of lime? (from mikky)

I have visited a gypsum mine for work, it came straight into the factory on conveyors and was made into plasterboard on site (British Gypsum near Battle), as far as I could see the gypsum went straight from powder , was inserted between 2 sheets of paper, then compressed to form the boards, now this may be a simplified explanation, but this was from what I saw, I didn't see many places to introduce other chemicals.
Grendel

The gypsum in plasterboard isn't hazardous as such, but the sulphate can react with organic waste to produce hydrogen sulphide (the stink bomb gas ) which is why it's no longer allowed in mixed landfill.

It won't raise the pH of soil like the calcium oxides, hydrated oxides and carbonates usually sold for the purpose, although it should help clay soils become less sticky.