The HomeBioGas fertilizer can just be automatically added to the irrigation feed.

Won't the irrigation feed get clogged because of the fertilizer? Or is the fertilizer that liquid?

Also in Israel retail gas is more expensive than retail electricity (which is due to gas monopoly).

Damn countries and their monopolies, in my country EDP has the monopoly of all energy related stuff, a few years ago the population started using less and less energy from them, probably because of solar pannels,etc... so they decided to raise the energy costs to keep their profits stable, our electricity is one of the most expansive ones in the world now...

efficient generator for this fairly small amount of power (max 4.4 kWh per day of gas).

Yeah, I searched around and couldn't find one either... Probably because natural gas is much less calorific than propane so there aren't any small generators efficient enough to really use BioGas :(