Blacker than coal!

In the desperate search for new sources of energy, natural gas from shale has sent many enterprises drilling away new areas, and not only in the US. But is this any cleaner source than coal?

Researchers at Cornell University are raising alarms over the expected increase in use of natural gas from shale deposits. They argue that replacing coal and gasoline with natural-gas alternatives could worsen, rather than improve, the impact of greenhouse gases. The greenhouse-gas footprint of shale gas over a 20-year period is at least 20 percent higher than that of coal and "perhaps more than twice as great," they say in a study published online in the journal Climatic Change.

To extract natural gas from shale, drillers hydraulically fracture the rock by injecting a cocktail of water and chemicals into a horizontally drilled well at high pressures. A significant amount of gas also mixes with the water-chemical mix and escapes into the atmosphere when the fluid returns to the surface. The drilling out of well plugs that separate fracking stages also results in temporary emission releases, giving shale gas a "significantly larger" greenhouse-gas footprint than conventional natural gas.

When burned to generate electricity, natural gas emits roughly half as much carbon dioxide per megawatt-hour as coal. But over its life cycle, natural gas could result in far more greenhouse-gas emissions, whether through intentional venting, equipment leaks, or fracking. And the leaks would consist of methane, which is a much more powerful greenhouse gas than carbon dioxide.

Of course, as the Cornell study points out, thera are ways that drillers and pipeline operations could reduce methane emissions by up to 90 percent. But, these technologies are currently not in wide use.

Well, the hunt goes on as an energy hungry civilisation keeps at it.