Surviving the effects of a natural or man made disaster or being lost or stranded in the wilderness often means making best use of available resources, whatever they may be. Les Stroud (Suvivorman) frequently touts the value of examining your environment to see what you can find that you can use. While Les often bewails the presence of man-made trash in the wilderness, he has found it is almost everywhere, and often yields things that can be used. Explore both the natural resources and man made debris. What is normally considered trash can be extremely valuable in a survival situation. "One man's trash is another man's treasure". Most of us throw out tin cans without giving them a second thought, but tin cans can be very useful and valuable in a survival situation. You can make a very efficient rocket stove from a single one-gallon can and a few soup cans. Tin cans can be used as cooking pots or to boil water to purify it for drinking, washing, or medical use. They can be flattened to patch holes in roofs or other shelters. They can be used to collect and store food when foraging. You might even use a tin can to dig a latrine if you don't have a shovel. In a dire emergency you might be able to use the ragged edge of a tin can as a substitute for a knife -- be sure to sterilize it first. The bottom of an aluminum beer or soda can can be polished (a little fine sand and a chocolate bar or tooth paste makes a good rubbing compound) and used as a parabolic reflector to focus sunlight to light a fire. Sometimes a plastic water bottle (with clear water or even urine inside) can be used to focus sun's rays to start a fire. Plastic bottles are always handy for storing and transporting water. Believe it or not you might even be able to boil water in a plastic bottle! As long as the melting point of the plastic is below 212F and there is water in the bottle, it should survive.
Les Stround (Survivorman) often laments the fact that just about anywhere you go, no matter how remote, you will find trash left behind by previous visitors. In a survival situation that is both bad news and good news. Bad news because trash is unsightly and may harm native plants and animals. Good news because it may provide useful resources. Trash can be a surprisingly good resource for survival tools. Discarded tin cans from food make good pots for cooking or boiling water. Larger cans might be used to build stoves that make cooking easier and more efficient or allow you to bring heat into a shelter where open fire would be too dangerous. They might be used as digging tools or flattened to cover holes in your shelter. You might be able to use them to make traps for edible insects and small animals. Even those loathsome plastic bags that take hundreds of years to decay in landfills can be useful in a survival situation and can provide shelter from the elements. Discarded wire may be used as lashing to create shelter or furniture or snares. You can sometimes find fishing line complete with hooks snagged in lakes and rivers or along the banks.
It wouldn't be possible or even feasible to list all of the ways you might use trash. The most important lesson to learn is to examine everything with an eye to how it might be used. Ask yourself "what can I do with this?" Some things are fairly obvious: tarps and plastic sheeting (or plastic bags) for shelter, paper, cardboard, and scrap wood for fuel for warmth and cooking, corrugated sheet metal for shelter but there are many other resources you might make use of in a survival situation. Tin cans have many, many uses. There are many components of disabled or abandoned vehicles that might be salvaged. Doors, hoods, etc., might be re-purposed for shelter; lubricants like transmission fluid and motor oil can be drained and used to lubricate other machinery or burned as fuel; upholstery and padding from seat cushions can be used for padding or insulation or sometimes to make shoes or clothing; wiring may be ripped out and used as cordage for building shelters; batteries, if they still have any charge, might be used with 0000 steel wool or with wires to create sparks for starting your fire. In a long term scenario, you might devise a way to use wind, water, or pedal power (like a bicycle) to turn a salvaged vehicle alternator to produce electricity and charge batteries. Pieces of glass headlight lenses might be used like a magnifying glass to concentrate sun's rays to light your fire or as scraping tools for cooking or preparing animal hides to make shelter or clothing. Even old newspapers can be used as insulation for a shelter or under your clothes or in your bed. Old newspaper makes surprisingly good insulation for both shelters and for your body. The only insulation in the walls of my grandfather's house in Idaho when I was growing up was old newspapers -- and winter temps got down as low as -26° but we never froze (and neither did the pipes in the house). They sure made interesting reading when we remodeled the old place.
Not long ago, a young Boy Scout survived being separated from his troop in freezing overnight temperatures in the Utah mountains by building a debris hut. A debris hut is very simple to build: just pile up a bunch of leaves and grass or pine needles and burrow into the pile or just lay down and cover yourself over with them. It will be a lot scratchier than a feather bed, but it could keep you warm enough to save your life. Also, make sure the debris is dry and free from insects. Hey, even a squirrel can build a debris hut! A large cardboard box can provide a surprising amount of protection as long as it doesn't get wet. I've seen winter survival sleeping bags made from trash bags and bubble wrap.
The most important concept is to take a careful inventory of ALL the resources you might have in a survival situation. They might be discarded items (trash) that you can make use of or natural resources that can be adapted for food, clothing, shelter, medicine, and fuel. You never know what might come in handy if you use your imagination and seek ways to make good use of anything you have available. In winter even snow can be a valuable resource. Not only can you melt it to get drinking water (as long as it isn't yellow or otherwise contaminated snow!), you can use it to build shelters to protect you from the elements. Be creative. You might even make snowballs to defend yourself from animals or other unwelcome intruders and perhaps you could even use them as weapon for hunting small game. Practice looking at discarded items and asking your self "What could I do with that?" instead of just turning away in revulsion thinking, "Ugh! Trash!" You will want to exercise some discretion. Partially filled beer and soda bottles found along roadsides might deliver an unpleasant surprise. Truckers have been know to use them as urinals to avoid stopping for a restroom break so that residual golden liquid in the Bud Light bottle might not be the left over brew you hope it is!
Use it up, wear it out, make do, or do without!
In SURVIVAL mode that might read: make do or die!