http://envirosponsible.com/
Here's a demonstration video of our rolling composter made from a used food barrel.

In an urban survival or bugging in scenario, composters like this one in the video would be worth their weight in gold. The same goes for our fecal matter. After a prolonged period of bugging in, dealing with waste would be a big issue. We'd quickly recognize the opportunity to compost our bodily wastes and use the nutrient rich, biologically inert compost in our victory gardens. By using composter, you can become more self-sufficient by being able to grow plants in an almost closed system with very little input. The carbon cycle would be observed once more.