KENYA'S mountains of plastic bags might not seem central to oil's grand narrative, but they are. Last week, the East African country banned almost everything about them: making them, importing them, selling them, using them, with penalties of up to four years in jail or fines up to US$38,000.

This type of prohibition carries a warning for an oil business that's depending on petrochemicals - and the plastics made from them - to pick up the slack when we all switch from gas guzzlers to electric cars. Saudi Aramco is betting its future on petrochemicals. The International Energy Agency thinks they'll drive crude sales for decades, accounting for 44 per cent of oil demand growth between 2015 and 2040.

But, as Kenya shows, the days of single-use plastic packaging may already be numbered. And with this stuff making up about a quarter of all the plastic used, that will have a profound impact on the petrochemicals industry. Environmental fears are only going to worsen. The Great Pacific Garbage Patch - a concentration of marine debris, most of which is plastics - is estimated to be roughly the size of Texas. There are similar areas, brought together by ocean currents, in the Atlantic and Indian Oceans and they aren't going anywhere.