The US Environmental Protection Agency (EPA) has finalised regulatory changes to allow the year-round sale of petrol blended with 15% ethanol (E15), ending the summer time ban that has been in place since 2011.

The EPA decision on 30 May ends the ban on E15 sales between 1 June to 15 September, which was introduced due to concerns that E15 contributed to smog in hot weather.

Reuters said the move was regarded as a win for the US farm hobby, which had argued that restrictions on E15 hurt farmers by limiting demand for corn-based ethanol.

“We estimate this one change will generate over a billion new gallons of ethanol demand in the next five years,” said Emily, Skor, chief executive of biofuel trade group Growth Energy.

However, the decision has drawn fire from the oil industry, which views biofuels as competition to petroleum-based fuels.

“Extending this waiver is an anti-consumer policy that risks causing costly engine and fuel system damage to nearly three out of four vehicles on the road today,” said Frank Macchiarola, vice president of downstream and industry operations, American Petroleum Institute (API).

“The EPA has left us no choice but to pursue legal action to get this unlawful rule overturned,” added Chet Thompson, the president and CEO of the American Fuel and Petrochemical Manufacturers trade group.

As part of the new regulation, the EPA also finalised reforms to the Renewable Identification Number (RIN) system to bring greater transparency to the market and deter price manipulation.

An RIN is a serial number attached to a biofuel to track its production, use and trading and is used to by refiners and importers of petrol or diesel to prove they have complied with blending mandates. RINs can be sold and traded separately from the biofuels that created them.

The EPA said its finalised RIN reforms included requiring public disclosure when RIN holdings exceed specified thresholds and collecting additional data to improve market transparency.

However, it stopped short of proposals to require buyers to sell off excess credits or limits to the types of traders that could enter the market, Reuters said.