Surviving Apocalypse & Natural disasters

This thread is about surviving a major disaster with science!

The objective of this thread is to post how you would survive with common everyday items.

an example is if you found yourself in a post apocalyptic or natural disaster situation how would you filter water, generate electricity, protect yourself with common items such as barells, buckets, pipes, copper wire and so on. Use your physics, chemistry, biology and engineering skills to survive.

Example:

Using animal fat as fuel for a diesel generator.

Lets hear what creative ways you would survive!