Oil prices have taken a tumble and the alternative energy IPO boom so strong earlier this year has dried up. So it's encouraging to see that Prometheus Energy is planning to list on AIM. Like many of it's American brethren, it is being drawn to London's AIM market, because of the high cost of regulatory compliance following the Sarbanes Oxley Act - something I've written about here before.

The company plans to extract waste methane from landfill and coal mines, liquefy it and turn it into transport fuel. This is all pretty low-tech stuff and I like it. Air pollution in cities would end in short order if cars, trucks and buses ran on natural gas rather than petroleum and especially diesel. Methane - the most powerful greenhouse gas - has very few impurities which create the particulates, or in layman's terms, the black stuff in your nostrils.

The environmental priority for cities is to reduce air pollution - not reduce carbon emissions which perversely encourages diesel. That's why companies like Prometheus are a step very much in the right direction.