Little more than 2 1/2 years from now, the global fleet ofmerchant ships has to reduce drastically how much sulfur ships'engines belch into the atmosphere. While that will do good things —like diminishing the threat of acid rain and helping asthmasufferers — there's a $60 billion sting in the tail.

That's how much more seaborne vessels may be forced to spendeach year on higher-quality fuel to comply with new emission rulesthat start in 2020, consultant Wood Mackenzie Ltd. estimates.For an industry that hauls everything from oil to steel to coal,higher operating costs will compound the financial strain oncash-strapped ship owners, whose vessels earn an average of 70%less than they did just before the 2008-09 recession.

The consequences may reach beyond the 90,000-ship merchantfleet, which handles about 90% of global trade. Possibleconfusion over which carriers comply with the new rules could leadto some vessels being barred from making deliveries, which woulddisrupt shipments, according to BIMCO, a grouprepresenting ship owners and operators in about 130 countries.Oil refiners still don't have enough capacity to supply all thefuel that would be needed, and few vessels have embarked on costlyretrofits.