Run Cars on Green Electricity, Not Natural Gas

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With today’s energy mix, PHEVs running on electricity from the grid are nearly three times more efficient than NGVs on a “well-to-wheel” basis—that is, when considering the full life cycle of the energy source, from fuel extraction to combustion to vehicle propulsion. This is because internal combustion engines, such as those used in natural gas vehicles and in today’s gas-powered automobile fleet, are incredibly inefficient. Only 20 percent or so of the energy in the fuel is used to move the vehicle. The other 80 percent is wasted as heat. Thus, choosing electric vehicles over NGVs can sharply reduce energy demand.

This important fact seems to have escaped T. Boone Pickens, the legendary oil tycoon from Texas who is now promoting a plan to replace natural gas in the electric power sector with wind-generated electricity and use the freed up natural gas to power a fleet of NGVs. Burning natural gas in a new combined cycle power plant is three times as efficient as burning natural gas in a car. Even including electrical losses from transmission, distribution, and battery charging, running a car on electricity from a natural gas power plant is more than twice as efficient. Keeping natural gas in the electric sector to help power a fleet of PHEVs is therefore the logical choice. Wind-generated electricity should replace electricity from coal-fired power plants, the most polluting power source.

Under normal driving conditions, well-to-wheel carbon dioxide emissions for vehicles running on electricity from natural gas–fired power plants are one fourth as high as emissions from cars directly burning natural gas. Since a PHEV operating in electric-only mode has no tailpipe emissions, electrifying transport would move the majority of carbon emissions from millions of vehicles to centralized electricity-generating plants, greatly simplifying the task of controlling emissions. As fossil-based power generation is replaced with wind and solar power, cumulative carbon emissions from centralized power facilities will be greatly reduced.

Carbon pollution is not the only environmental concern. Over the last decade, the decline in U.S. conventional natural gas production has been offset by turning to more unconventional sources, such as coalbed methane, tight sandstones, and gas shales. Between 1998 and 2007, this unconventional production increased from 28 to 47 percent of total output. Growing reliance on gas shales in particular is raising concerns about water consumption and contamination. Extracting gas from this source involves hydraulic fracturing, a process that injects water, sand, and chemicals into the shale layer at extremely high pressures. The process can use millions of gallons of water per extraction well and is known to leak chemicals into surrounding aquifers. The Commissioner of the Department of Environmental Protection for New York City recently wrote to the New York State Department of Environmental Conservation voicing concerns that drilling for natural gas in the Marcellus Shale formation will contaminate New York City’s watershed, jeopardizing drinking water. Opposition to unconventional production is likely to rise as gas companies attempt to expand operations into increasingly sensitive areas.

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