A study funded by Rice’s Energy and Environment Initiative found that use of compressed natural gas in vehicles yielded the least benefit. The emission matches that of modern gasoline or diesel engines.
The study was carried out by environmental engineer Daniel Cohan and alumnus Shayak Sengupta. They found that, when coal-fired power plants were replaced by gas-fired power plants, more than 50% reduction was found in net emissions.
The objective is to show the huge difference reducing highly uncertain leaks can make in reducing emissions. The observation also showed how new natural-gas power plants are responsible for less than half as much greenhouse gas per kilowatt hour of electricity generated as existing coal power plants.
Analysis of transportation fuel showed natural-gas-burning and gasoline-burning vehicles were nearly identical in emissions impact. Calculations were modeled on Honda Civics, which are sold in both configurations as well as a gas-electric hybrid. In the latter case, the hybrid had a 27 percent lower emissions impact than the natural-gas version, due to its better fuel economy.
According to Rice University, the researchers’ calculations considered emissions from production and transport of each fuel to combustion, including leaks of methane.
Comparison was made among five sectors – power plants, furnaces, exports for electricity generation overseas, buses and cars, to see which use of natural gas pays the greatest dividend for reducing greenhouse gas emissions.
A comparison of natural-gas-burning versus diesel-burning buses gave the emissions edge to diesel, which accounted for 12 percent fewer emissions, within the range of uncertainty. At the same time, replacing old oil-burning furnaces for residential heating with new natural-gas-burning models yielded emissions savings of up to 48 percent.
Cohan said, “This research is aimed at a world where natural gas has become more abundant. Natural-gas vehicles yield the least savings, and require building out infrastructure that doesn’t transition into new renewable options.”
Therefore, a more effective way to use natural gas to reduce climate-warming emissions would be in furnaces and power plants.
Image/Graphics credit: Tanyia Johnson/Rice University
