Like I said, natural gas is an immediate stopgap solution with 60% less carbon dioxide emmissions than gasoline or diesel per unit of energy delivered. It currently is abundant, and we have a 30,000 year supply in the Burmuda Triangle. Oil companies do not want the natural gas compressors to fuel cars at their stations? It is easier to sell gasoline and diesel. So, the gas industry is trying to get fleet users to convert which would cut imported oil by 60%, and cut gasoline/diesel use totals by 25%. It is a start. However, you do know that Exxon has spent I think $250 or $550 million on an algae oil farm. Seems like they are going to get into algae oil which is very productive. Current costs are about $2 a gallon to produce. It needs to get below $1.70 a gallon to be cost effective. Scientists are trying to breed algae to produce more body oil so the cost can come down below the drilling costs. It is almost at the breakeven point to stop drilling. Algae is carbon neutral which takes carbon out of the air while the algae is growing, but puts it back in when the algae fuel is burned. To convert all of American vehicle use to algae oil fuel would take greenhouses to cover an area the size of Rhode Island to produce. Not to bad, just have a lot of them around the country, but they still need to be close to a water supply and refineries.
As oil prices continue to rise, technology will increase the MPG of vehicles, and algae oil will probably be what takes over first. Our whole infrastructure not just in America, but world wide is set up for liquid fuels with pipelines, refineries, storage facilities, and oil tankers. That is why algae oil production will eventually take over. It is far more efficient than ethynol production.
Of course natural gas can be produced from cow manure and seaweed. 1/3 of all our natural gas use can currently be made from cow manure collected from feed stalls and dairy farms. However is is twice the price to produce than drilling/fracking. It has already been tried in Oklahoma at two feed stall locations, but it is labor intensive, and costs more to produce still than drilling. Another alternative is we have discovered a seaweed that grows 6' per day. It can be harvested and used to produce natural gas. It two is labor intensive. Using sewage to produce natural gas would only yeild about 5% of our gas needs. Humans just do not produce as much gas as cows.
So, we have stopgaps that can be used now with tax incentives for installing ng compressors and using ng vehicles for fleets especially. Then incentives for using algae oil is close to being cost effective.
Going to all electric vehicles would require an additional 20-30% more electric production nationwide for recharging. Vehicles do not have the range, low cost investment, and quick recharge ability that natural gas or algae fuel would have.