I would encourage the use of a gasoline generator that the engine was rated for very minimal pollution. I use both electric and gasoline motors to build human+other hybrid powered bicycles and there is a huge difference in how cleanly different small engines burn their gasoline. Also, consider something capable of running on E85 or better if you have access to fuel alcohol or propane or liquid natural gas all of which burn many, many, many times cleaner then gasoline.
I am by no means apposed to liquid combustion fueled power sources. But a simple choice in brand name can make the difference between producing less pollution then a modern gasoline car or more then a modern gasoline car with your set-up.
As to home generator built set-ups I would like to point out that older model car alternators especially those from the late 70's early 80's period (new replacement parts from auto shop) are capable of producing substantially more voltage then they are rated for since they used the methodology of controlling the field coils power to control the output voltage and with some modifications to the voltage controller unit it is possible to produce anything from 6-120 volts charge from them just by adjusting the field strength (they are not permanent magnet generators but rather use an electric magnet field coil instead and adjusting the power supplied to that field coil adjusts the voltage that is generated).