Has anyone suggested to Sir Richard that a 4 engine jet uses quite a bit more fuel than a two engine jet?

Another point. Biodiesel may be the better choice, but it's necessarily the best choice. It holds water much like ethanol and therefore needs an anti-ice agent in the fuel. You can ask Speedishuttle in HI, particularly Maui. They used BD for a while and cause havoc with their Mercedes/Dodge vans.