As of Jan. 1, Ontario will join Quebec and California's carbon market, which has also seen three sold out auctions in a row for current credits.

The June auction in the system aimed at lowering greenhouse gas emissions follows the inaugural one in March, which also sold out.

Ontario's first cap-and-trade auction sold out all current allowances, giving the new market a strong start, but the province's environment minister warned the real test of the system will be in the emission reductions it brings about.