Using a petrol powered motor

Hi everyone,
I am about to embark on building a shredder machine (in London if anyone wants to meet up) and I am interested in the possibility of using a small engine (e.g. a 50cc from an old moped). Obviously I’d prefer not to use petrol but I’m interested in this application as a way to remotely shred when not connected to the grid (I also considered renewables but you need quite a lot of power to drive some of the motors people have been suggesting). Also (I work in international development), I am thinking of this projects application in countries where grid electricity is less reliable, motor parts may not necessarily be affordable/available and people are very comfortable with fixing/maintaining mopeds etc.

Any thoughts on this – particularly how to step-down the high rpm of a 50cc motor to get in the right rpm and torque range – would be much appreciated. As an example I have quickly googled and seen that the following 50cc moped has a torque of 3Nm at 5000 rpm.
http://www.globalsources.com/si/AS/Chongqing-Loncin/6008801833032/pdtl/Scooter/1003277691.htm

Why not just use the gearbox and rear wheel shaft from the moped to connect to the shredder, they are usually a single unit. In low gear the wheel should turn at about the right speed and you should have around 2HP of power

Yes that seems like a good first test. I’ll come back with some findings – cheers!