Only ten years ago about a half of power production of the USA was coal. Today this figure fell to one third. For the same period of time power generation from natural gas increased approximately from 20% up to 33%. As expected, this tendency will proceed. But though natural gas when burning emits less carbon dioxide, than coal, it doesn’t mean that other emissions are harmless to the environment. Experience of the last five years showed that, in particular, emissions of methane can limit climatic benefits of replacement of coal with natural gas.
To determine whether really natural gas is less dangerous to the environment, than coal, scientists from Carnegie Mellon University (USA) carried out new assessment of emissions of methane and compared climatic benefits of use of natural gas instead of coal for electricity generation.
“Results show that the power plants of the combined cycle using natural gas can have lower impact on climate, than coal power plants until intensity of a leakage of methane isn’t really high” — the leading author of work Devayn Farkukharson says.
Scientists simulated lifecycle of emissions of methane and carbon dioxide from new coal-dust power plant, power plant of the combined cycle with steam-gas installation and ultra-supercritical coal-dust power plant taking into account and without capture and sequestration of carbon (English carbon capture sequestration (CCS)). Using this model, the team measured climatic impacts of each of options in the century range, and also estimated influence of various speeds of a leakage of methane ranging from 1% to 5%.
If the previous researches set as the purpose identification of pluses and minuses of use of natural gas, then the comparative analysis published in the August issue of the Industrial Ecology magazine differs in the fact that in it four various climatic indicators are used: potential of global warming, the cumulative radiating impact, potential of technology of warming and global change of temperature.
“Without CCS all measurements show that power plants of the combined cycle with methane leak coefficient lower than 8,5% have lower impact on climate, than coal-dust or ultra-supercritical coal-dust power plants, within 100 years — Farkukharson explains. — However with CCS inclusion coal-dust power plants and coal-dust ultra-supercritical will have lower impact on climate, than using natural gas with CCS if the speed of leak of methane exceeds 2% of the natural gas used by power plant”.
Thus, it is impossible to consider unambiguously natural gas the best decision for power production.
“Our results demonstrate that new gas power plants, most likely, have smaller impact on climate, than coal, even taking into account methane leak. Nevertheless the deep obezuglerozhivaniye of the energy sector will probably demand radical transition from fossil types of fuel, including natural gas”.