This makes regular power plants unecessary and obsolete, solving the intermittency problem with wind, water, and solar power.

http://thefraserdomain.typepad.com/energy/2006/12/westinghouse_wi.html#comment-26871562

But are biogas resources too small to backup wind, solar, and water power?  yep, most likely they are, but not because digestion loses energy.  Manure and farm waste alone would supply a large percentage of backup biogas.  Especially when the biogas is used at 75% efficiency.

Where does the rest of the biofuel come from so that natural gas is conserved as long as possible?

From algae in solar collectors.  Half of the dry weight of the algae is biodiesel, the other half is cellulose powder.  The biodiesel could power the fuel cell vehicles in driving mode, the powdered cellulose, biogas (with natural gas as a backup fuel) in stationery V2G mode.

In v2G the CO2 could be sequestered in the algae system.

The energy lost in bacterial conversion of coal and oil to natural gas would be less than the energy expended in conventional mining and refining.  and all that toxic mess that comes with coal and oil would stay far underground where it is already.  The natural gas would carry the energy in the coal and oil to the fuel cells.

Yep nukes are all TOO real Dem!  Too bad for all of us. 

Fuel cost?  Biogas in a fuel cell/turbine is around 5 cents per kwh, powdered cellulose from algae is even cheaper.  Biodiesel from algae will be cheaper than diesel or biodiesel from fuel farming. 

In plugin/fuel cell cars that use 1/10nth of the fuel on average of an equivalent ICE car, biodiesel from algae can  provide more than enough liquid fuel for transportation needs.

Manure and waste to biogas. Biogas to electricity and cO2.  CO2 to algae biofuel.  Biofuel to electricity and cO2.  CO2 back to biofuel. It's a cycle. 

While it is true that if the grid is mainly powered by solar, wind, and wave power the whole capacity of the grid may need to ocasionally come from a backup source.  V2G does that with no duplication of generating capacity.

A big argument with renewables is that if you aproach 100% renewable power on the grid, you also need storage and generation capacity that equals that capacity.  in other words you would need all the present power plants idling in case the wind, water, and solar power dissapears all at once all over the grid.  And that cost of maintaining those plants in that idling state would negate all the savings from renewables.

By using v2G to supply this emergency backup generation that duplication of generating capacity does not take double the capital investment.  Because the vehicles are already payed for by consumers for their transportation function.  The V2G mode is a free bonus.

Trillions can also be saved by going to this distributed power generation and storage grid design, because it not only dispenses with power plants, but makes hugely expensive grid upgrades unecessary.

Each home with v2G becomes a neighborhood power system that can power that local grid.  And it builds out in blocks from there.  Also protecting from ever more frequent power outages due to increased storms from global climate change.

The profit potential of a home, small business, or farm that uses biogas digestors, V2G, wind, and solar power all together is enormous.  It allows an individual V2G/renewable supplier or local renewable energy cooperative to guarantee a set minimum amount of power to the grid, making renewables just as reliable as advocates claim  fossil and nuclear power are.