With high natural gas prices showing no signs of abating and supplies becoming harder to obtain, cheaper and dirtier alternatives to the fuel are looking increasingly tempting for energy-hungry buyers.

Liquefied natural gas prices in Asia are now at about $50 (¥6,665) per million British thermal units. On an energy-equivalent basis, gas was at about double the price of diesel as of early August, with high-sulfur fuel oil and coal cheaper still, according to data from S&P Global Commodity Insights.

In Europe, the situation is similar, with natural gas at around $60, at least triple the price of HSFO and propane, according to energy consultancy FGE.