But has he prooved there is only lubrication oil in there, oil also burns, maybe the methane bubble is just for show and he has actually converted the engine to some sort of diesel/ethanol/any other oil engine! ;D
I want to se the engine stop when the ballon is empty! :\
Also now I watched the video: he spends more energy collecting the gas than it would have taken him to use a regular bike. But fun idea.