From reading about van living, people often have a bucket for emergency defecations. And people on the road say they often go months and months without needing to use it. Toilet issues seem to be the greatest fear of people going into van living, but eventually discovered to be a non-issue, from recaps I've read.
Every time you buy anything at a store, you get a plastic bag. In an emergency, just crap in one of those. Place the used paper on top, tie the handles together, and find a dumpster. Really not that terrible.
> Every time you buy anything at a store, you get a plastic bag.
In some countries that is true, in others you have to choose to pay for a bag, so most people don't, instead they re-use their existing (non-plastic) bag.
The UK for example charges 5p for a plastic bag and this has had a significant effect:
Some people use $50-100 portable toilets, but others favour what is essentially a bucket with a toilet-styled lid, lined with multiple heavy duty plastic bags, and then filled with cat litter or dirt.