The states of digi cash in he hand held

Digi cash is either on the secure personal balance, or, it is in the instruction cache, at risk of a timeout or recall within timeout. Those deal failures have semi predictable costs, fails to deliver do happen. It is a bounded system, cash never disappears unless the currency regime allows it, or your thumb print expires.. Whether you can erase cash depends on the cash rules on the currency regime.

Current:

In the United States, burning banknotes is prohibited under 18 U.S.C. § 333: Mutilation of national bank obligations, which includes "any other thing" that renders a note "unfit to be reissued".

So, it is up to the New Fed to change the rule, I see o reason for them to do so. 

The congestion process of making change, it is processor intensive, disassembly and reassembly. There is a network congest problem in the sudden rush to cash, and this depends on the ledger system behind the scenes. Consumers make change but report cash balances weekly rule might suffice.  Enough room to manage banks swaps during a rush to cash.

The New Fed can limit cache timeouts.  Another way to distort currency markets, keep digi cash in the cache on some external promise. The card can enforce cache timeout. The default position is off, and the feature enabled via thumb print volition. But these simple limits are exposed, and Swift will use them.