Bloomberg news reports that  European Union carbon permits dropped to their second-lowest close ever, after the bloc canceled an auction of permits for the first time as bids failed to reach a secret reserve price.

The sale was called off because the price would have cleared “significantly” below the prevailing market rate, according to European Energy Exchange AG, the unit of Deutsche Boerse AG that runs the auction. EU allowances for delivery in December fell 5.6 percent to close at 3.73 euros ($4.86) a metric ton on London’s ICE Futures Europe, having earlier dropped as much as 6.1 percent. The contract closed as low as 3.42 euros on Jan. 31.

Carbon has plunged almost 90 percent in the past five years as the euro area’s second recession since 2008 cut industrial demand for permits, contributing to an oversupply that EU lawmakers are struggling to fix. Failed auctions may push the cost of emitting carbon dioxide even lower as unsold credits are held over for the next four sales under EU rules.