Allowance destruction consists of permanently removing an allowance from the European trading system. This allowance can never again be bought, sold, or used by an industrial polluter to emit greenhouse gases. This is equivalent to permanently reducing a part of the available supply: The allowances are no longer simply "confiscated" during the investment period, they are definitively eliminated.
This means you will not be able to resell them: the value of the destructed allowance is permanently lost. It is a radical method for permanently reducing the CO2 emissions budget in Europe. Some of our users destroy a portion of their allowances (often representing a part of their capital gain) to offset their own emissions.