NEW YORK: The price of very low-sulfur fuel oil has risen in recent months, a sign of increasing worry there is not enough of the fuel to comply with new global shipping laws that took effect this year, market participants said.

Very low-sulfur fuel oil (VLSFO) lately has started to trade at levels comparable to marine gasoil, a type of diesel fuel used by tankers. That is an indication that refineries may need to increase production of VLSFO as tankers shift from dirtier, high-sulfur fuel to a cleaner product to comply with International Maritime Organization regulations designed to reduce smog.

Under those rules, shippers either need to use fuels with a sulfur content not exceeding 0.5 percent, or install scrubbers that can clean higher-sulfur fuels to reduce emissions. The rules, known as IMO 2020, affect more than 50,000 merchant ships worldwide.

Supply has tightened in trading markets in Asia and Europe and now in the US. On Wednesday VLSFO in Houston traded at $642 per ton, compared with $667 per ton for marine gasoil, S&P Global Platts data showed. That $25 spread was at $152 half a year ago. That suggests not enough VLSFO is being produced and raises concerns about supply this coming spring when refiners go into maintenance season, said Rick Joswick, head of oil pricing and trade flow analytics at S&P Global Platts in New York.

The spread in Singapore has narrowed to $15, while in Rotterdam it has narrowed to $3, S&P Global Platts data showed.

Meanwhile, VLSFO stocks are also falling, Joswick said.

“You can’t cover demand out of inventory forever,” he said. “Production has to pick up and trade flows have to shift.”

“It means marine gasoil needs to be called upon to cover some of that demand,” Joswick added.

The spread between VLSFO and high-sulfur fuel used by shippers that installed scrubbers was $330 per ton in Singapore and $272 per ton in Houston, S&P Global Platts data showed. That spread was greater than shipowners expected, benefiting tanker operators that installed scrubbers, shipping sources said.

VLSFO demand could prompt refiners to increase supplies later this year, said Andy Lipow, president of Lipow Oil Associates in Houston. “This is a nice, high price for VLSFO. We’ll reach some new equilibrium,” he said.