The grid is a word search, but instead of looking for words, you are looking for chemical structures. The grid is large but looking just at the letters that are single-letter chemical elements finds all the structures.

Grid with structures highlighted

The IUPAC name of each chemical (clued by the flavortext) can be filled in to the blanks below the grid as follows:

Taking the designated letters in the order given results in GLOBAL CARBON CYCLE.