History has shown that cash is not always king.
In the event of systemic failure on a large scale, traditional means of payment in commerce and trade often become devalued. As an example, in some communities devastated by Hurricane Katrina, a barter economy almost immediately sprang up, to the point where cash was not the currency of choice.
It was reported that gasoline, cigarettes, and beer became the commodities in greatest demand via barter transactions. I suspect that if those communities had been isolated long enough, some other genuine necessities would have risen in comparative value over those items. Think "supply and demand."
Trade Doesn't Halt After a Disaster
Even if you believe yourself to be fully prepared for disaster, I suspect you could still quickly find yourself in serious need of some item or service that was unanticipated. Perhaps it would be specialized medical needs, mechanical parts, or a ride to safety. No one can ever be fully prepared for all possibilities.
That means besides simply stocking up on food and water and prescription meds, the prudent preparer also considers the need to have on hand alternative forms of currency. Depending on what it is, it could serve as needed in the role of household sustenance, neighborly charity, or as a barterable commodity.
The possibilities are endless ... and it might be wise to have several options on hand--quantities based on personal preference and the amount of time you want to abide ...
1. Of course, some good old foldable U.S. currency IS advisable to have on hand in every household. For although it might become less valued in long-term scenarios, it will be far more likely that a shorter term crisis situation would call for this traditional means of payment. (Note that you probably don't want to count on credit card, cash card, or check-writing to be accepted, especially if there are power outages.) Just make sure you have your stash adequately hidden and secured.
2. At the opposite extreme, precious metals such as government-minted gold and silver coinage are seen by many as a longer term, safe store of wealth, easily recognized as a historical basis for trade, readily quantifiable and transportable, etc. If you choose to hold precious metals for the purpose of crisis preparedness, it is advisable that you literally, physically have them in your possession ... again, safely secured.
3. Practical skills and expertise in any number of areas, along with needed tools, can be a tradeable commodity in challenging times. Of course it could be difficult to control the demand on your time in some cases. For instance, medical professionals may be overwhelmed in some locations in worst-case events.
4. Water, and the means to draw it and purify it could prove to be in extreme demand in many events, as city water systems can fail or be compromised. In the massive power failure experienced in the northeastern U.S. and Canada in 2003, the municipal water supply for Cleveland, Ohio, immediately failed, putting at risk a million local residents. A short-term solution is to have pure water stored for your family. Beyond that, if you have a means for purifying water, you could find yourself well ahead of the Joneses, making new friends in the neighborhood you never even knew lived there before. Further, if you have a well with a hand pump or the ability to generate power for an electric well pump, you could find yourself in business and able to acquire whatever necessities you might require in trade.
5. Food quickly becomes a high-demand item in medium and longer-term situations since refrigerated and frozen food that so many count on today can spoil ... in addition, the means for adequately preparing those foods would often be lacking. In fact, we see in the recent hurricane aftermaths how an unbelievable number of families don't bother to have on hand a few days of food of any kind to weather a breakdown in the local grocery and restaurant supply chains. Again, if you have stored, convenient foods in quantity, you are ahead of the game.
6. I hate to mention it again, but substances that people can become addicted to will always be in extreme demand when they are not available at the local markets. Beer, booze, tobacco, and coffee are items you might consider having on hand in some reasonable quantity, even if you don't use them yourself, as commodities for trade.
7. Gasoline is a commodity that can certainly become highly valuable should local supplies become interrupted. The problem is that it is tough to store safely and for any great length of time. It's a good idea to have several gallons on hand for personal emergency usage (treat the gas with PRI-G or the equivalent, rotate it periodically, and keep it outside of your living space and away from sources of ignition). Whether you have a few gallons or you opt to store more, be sure to research and follow local laws and regulations for safety's sake.
8. Anything and everything else can become objects for trade in the right conditions. Consider the scenarios where examples such as these might be in high demand: toilet paper, over-the-counter pain medications, first aid supplies, batteries, flashlights, hand tools, plastic sheeting, cleaning and disinfectant products, personal hygiene items, disposable gloves and masks, firewood, lumber, ammunition, vegetable seeds, lighters, matches, and the list goes on and on.
I'm not advocating you go out and "hoard" anything with an eye toward one day making a killing in an impoverished environment. But simply use some common sense and be aware that even economies are transformed in disasters ... better you are aware and ready.
As I alluded to early on, some of these items would be in such extreme need in some cases that it would be immoral to withhold them from anyone in dire need of them. Most folks would be only too happy to help in their communities in any way possible in a true disaster. Being prepared means you are in that position to help as opposed to being one of the ones seeking someone else willing to give aid.