Biodiesel has been trialled in an aeroplane engine in France, and reported on the Green Car Congress, CFM a joint venture between Snecma and General Electric, carried out the test on one of its CFM56-7B engine using an ester-type biofuel at Snecma's Villaroche facility near Paris.
CFM said:
The biofuel used for this test is 30 percent vegetable oil methyl ester blended with 70 percent conventional Jet-A1 fuel. This test was designed to check the operation of a jet engine using a fuel made from biomass, without making any technical changes to the engine. With this type of biofuel, the target is a net reduction of 20 percent in carbon dioxide (CO2) emissions compared with current fuels.
No comments about adding filters or changing fuel lines here, you'll notice. But being a Derby boy and living within earshot of Wilmore Road, where Rolls Royce tests its engines, for my formative years I can tell you it takes many hours/consecutive days of testing before they're satisfied that an engine is OK.