By Jane Wakefield Source: BBC
Green entrepreneur Arthur Kay wants the red buses that have become a landmark of London to run on fuel generated by coffee waste.
He runs Biobean, a start-up which is gathering waste from coffee chains such as Costa and converting it into liquid fuel.
The firm is due to unveil a coffee-run bus in the capital in a few weeks.
In London, the need to get cleaner air is vital - the dense road network coupled with high buildings make it one of the most polluted places in the UK.
And, said Mr Kay, there is always a ready supply of ingredients.
"As long as people are still drinking coffee, there will be coffee waste.
Could London buses be run on coffee waste?