Pretty sure biodiesel isn't a reasonable option - the extra bulk and mass to make a safe diesel-style engine would make a chainsaw unbearably heavy. Plus you'd

Pretty sure biodiesel isn't a reasonable option - the extra bulk and mass to make a safe diesel-style engine would make a chainsaw unbearably heavy. Plus you'd have wicked problems with fuel gelling in cold weather. Alcohol is possible - but it'd probably be a considerable overhaul. Most stock saws really don't want to run on gasoline that has any ethanol mixed in, although you can use E10 if you have to. And really you should be using at least 89 octane, if not the 91 high-grade stuff. Chainsaws are also all pretty much two-stroke, so you'd have to keep a stock of the mix-in oil, or you're going to destroy your crankcase and pistons. Also, unless you want to burn up your saw bar and chain, as its whirling around at thousands of RPM, you need to have a good stock of either actual bar and chain oil, or, in a pinch, regular 20/30 wt engine oil.