I would accept "Can be depolymerized, and absorbed by the biosphere or water table or bonded to alkaline rock, when suspended in normal soil in a temperate clim

I would accept "Can be depolymerized, and absorbed by the biosphere or water table or bonded to alkaline rock, when suspended in normal soil in a temperate climate in less than 100 years" as a victory here. Lactic acid is in milk/yogurt/etc.