Here is the full list of all 20 GNOG achievements. It takes around 1-2 hours to unlock all of the achievements on Windows.
Leave no trace
Keep the kitchen clean
Please don't bother the amphibians
Test the astronaut for space sickness
Leave no worm behind
Watch what you eat
Finish the game
Complete HOM-3
Unlock every level
Complete CANDY
Complete EATER
Complete PURP-L
Complete LAB-O
Daydream at the blackboard
Complete LOG
Complete VORT-X
Complete SUB-01
Discover what lurks below
Experiment in the studio
Complete FRG-Y