a diesel engine is designed to be run on low quality unrefined fuel. (i.e. pretty much anything. some people get free used soy oil by asking nicely at fish & chip shops, and run thier car on that.) here is a more hitech solution.

using cellulose digesting enzymes to break down fibrous material which would other wise go to complete waste, timber offcuts, grass, corn husks etc. enzymes could be bred to suit locally available byproducts and fuel would not need to be transported long distances.

Researchers from Auckland recently “discovered” what the Bougainvilleans already knew – that coconut oil works just like diesel. It’s a bit cold to grow coconuts here, though.