Great Western Coffee Shop

France’s first trains fuelled by vegetable oil as a replacement for diesel began operating today on the line between Paris and Granville on the Normandy coast.

The local newspaper Ouest-France reports that the switch from diesel to rapeseed oil (colza) is experimental for a period of three months.

It quotes an SNCF official as saying no modification to the locomotives has been required.

I am doubtful as to the merits of this.
If USED (or otherwise unfit for food use) vegetable oil is used, then re-use as fuel is a good idea, rather than dumping in landfill.
However supplies of such oil are inherently limited. If rapeseed or other oils are grown for use as fuel, then that in my view is a bad idea as production of human food is thereby replaced, in a world where many are already going hungry.

Also a lot of fossil fuel is used in the cultivation and processing of the crop.

I would prefer to see busy routes electrified, with battery power for lightly used branches or areas otherwise problematic to electrify.

The conversion of vegetable oil into fuel oil has been around for a number of years

Agree, there is a well understood process whereby veg oil may be turned into biodiesel, this involves sodium hydroxide and methanol, both rather nasty materials. This also produces glycerin as a by product.
The process is potentially hazardous especially when done at home without proper precautions.

Alternatively straight vegetable oil without any treatment beyond filtering can be burnt in some diesel engines, usually only in warm conditions.

A small percentage of vegetable oil can be added to fossil fuel diesel and burnt in most standard engines.

However for reasons already given I am not keen on this.

Slightly relevant trivia, the first diesel engine ran on peanut oil !