Artists and plastic.

Nope your not the only one! I have found the bases of a well known brand of chocolate allegedly beloved of diplomats (trying not to advertise!!!) make great pallets! I also use old plastic tubs to keep my acrylic paint moist. I mostly save glass though - jam jars, spice jars (make great portable water containers for out and about) and handy little glass pudding dishes. The plastic that really worries me though is acrylic paint - how best to dispose of any water. I use disposable pallets mostly which means I'm not having to clean them but brushes still need to be cleaned.

Always difficult to dispose of plastic in such a way as to ensure so far as you can that it doesn't end up in the sea killing things. I try to buy as little plastic as I can, but, like you, I use plastic for arty and non-arty purposes. A tub which contained Kelly's ice-cream (we have our weaknesses) is an improvised soap-dish. Containers which held my Sunday joint are re-purposed as water holders when I paint in watercolour, gouache or acrylic. A very heavy piece of plastic from a window-replacement company is a handy brush-holder. Old credit cards are used to scratch areas of watercolour or acrylic, even to manipulate oil paint (messy: can't advise it). The edge of a credit card can be used to print very liquid (but not TOO liquid) paint, if your rigger-hand shakes. (That doesn't even need an old credit card: your current one won't be hurt if you use it for that purpose: MUCH better than using it for its intended one.) Re-using plastic is one of many things we can do to improve - or at least stop damaging - the environment: and it will do much more, very much more, than banning solvents, metals in paint, and all the other things that people get in a lather about. (And I say this as one who has given up solvents with oil paint - thus removing any need for water miscible oils altogether.)

An empty glass marmalade pot for holding water for indoor painting, had this for years, and another smaller one, which has never leaked, for my art bag when out-doors. Anything that can be burnt goes in the recycling bin and made into a firelighter. All non-recyclables I take to the recycling centre.