If the system is running off biogas, then it is as green as can be while still using a hydrocarbon fuel, so what's the beef? It's definitely cleaner than burning coal or diesel, and its localized generation means that you don't have to pay for, or compensate for, the transmission grid losses.
As for the sell costs, that's a management problem, not a technology problem. The current pricing structure will get modified as more customers generate their own power. Eventually, there will simply be less "float" to make a profit from. Additionally, if more people crank up their natural gas usage, the operating margins will also get thinner. Note that as with standard electric generation, if there is no demand, cranking the generator simply wastes fuel. I expect that as the industry matures, every generator will have a throttle limit that does not allow the generator to pump energy into the grid if there is insufficient demand.
We can either built more power plants, nuclear or otherwise, or you can install a 10 kW system in your own home for $3K, if the pricing works out the way they hope. That would be about 1/20 of the cost of a typical solar cell installation for only about 6kW generation. You can use it all, or you can sell to the utility, assuming there's sufficient operating margin.
TTFN
FAQ731-376