How to make dichloromethane human-friendly and safe for storage? I use dichloromethane to polish 3D printed object as postprocessing step.
Most of it is stored in darkened glass on my balcony (now at $\pu{-15^\circ C}$).

What chemical reactions I need to make it human-friendly (non toxic)? Is it ok to use non-darkened polypropylene/polyethylene box to store it? 

What I can do during the summer season? (Dichloromethane is volatile liquid)
According to A Comprehensive Guide to the Hazardous Properties of Chemical Substances at pages 445-446:

Disposal/Destruction
...
Small amounts may be destroyed in the laboratory by hydrolyzing with ethanolic solution of potassium hydroxide