How to dispose Damage, torn idols of God? (Khandit pratima)

As per modern and concerned learned Hindu Brahmin as well as some Christian Priests, Below are relevant options.
Many Gurujis of ISKON and other Math recommend disposing them in to flowing waterbody/ streams or rivers.
But that was relevant to earlier days when idols were mostly clay or wooden which would decompose properly into water, but now a days different materials are used which takes 500 or more years to decompose like plastics, fibers and other materials, and think about even 5% of the world;s population dumping them into flowing water and the result on our environment! I wouldn't dare.

So below are more scientifically as well logical justification.

• Dos' - Dig it into soil/ garden or burn it down in a metal bowl and spread the ashes under plants, garden soil. 

(Preferably avoid plastic Gods even as plastic is the enemy of this Environment and worst invention to affect Mankind as I believe,)

• Dont's - Dispose in water, dispose under tree/ peepal tree.

..