Hey there! That's actually a really important question that doesn't get discussed enough in our communities. I've seen some close calls with trash cans smoldering after someone tossed what they thought were "cool" coals from their weekend barbecue.
The absolute safest approach is to let coals cool completely for at least 48 hours in your metal grill or a dedicated metal container. Once they're cold to the touch, you can double-wrap them in aluminum foil before placing them in your regular trash. Many cities are now installing special metal bins specifically for ash and coal disposal in parks and public spaces - these are your best bet when available.
What we really need is better public education through clear signage near trash receptacles and community reminders about fire risks. Some neighborhoods have even started "Cool Coal Saturday" programs where residents can bring cooled coals to designated collection sites. Remember, that momentary convenience of tossing a "mostly cool" coal could literally set your community's trash collection system on fire - and nobody wants that responsibility!