OK, being a long time backpacker/mountaineer, I can't resist.
All this talk of buckets, plastic bags and kitty liter is just too much.
Try this in your SHTF event and see who cares.
Even in an apartment complex, walk into your "yard" (PC landscaped border around said apt complex), best in the "bushes", with gun if you feel it necessary, mostly in the evening, but in the day light if necessary, dig a hole, take a ...., cover it up, go back inside, and wait for a telephone call or a visit from the defecation police.
What is it that US culture can't grasp about the fact that, for thousands of years, no, wait, hundreds of thousands of years, our species took a **** with no buckets, no plastic bags and no kitty liter?
They simply squated and did it.
What's the real issue here? PC during a SHTF?
Do you really think it's going to matter?
Wake up and smell the coffee.
And if you can't smell the coffee, then your hole wasn't deep enough.