The Post-Carbon Institute has published a report which claims to shatter the "myth" that natural gas can be a bridge fuel between oil and coal and a renewable energy future for the United States.

Without gas from shale, the US Energy Information Administration estimates that gas production will fall by 20% by 2035. However, replacing coal would require a 64% increase in gas production and replacing oil another 100%.

Extraction of shale gas requires high energy and water inputs – and the wells rapidly become depleted.. It involves controversial hydraulic fracturing and the need to dispose of toxic drilling fluids produced from the wells. Full-cycle greenhouse gas emissions from shale gas may possibly worse than from coal. And the cost of shale gas production is well above current gas prices.

Converting to gas would also require massive new infrastructure, including gas storage, refueling facilities and pipelines which the report describes as "a logistical, geological, environmental, and financial pipe dream" (apparently no pun intended).

The Report concludes that strategies for energy sustainability must focus on reducing energy demand and optimizing the use of those fuels that must be burnt.

For example, more than half of the coal-fired power plants in the US are more than 42 years old and 21% of coal-fired capacity will have to be retired under new rgulations which take effect in 2015. Adopting best-in-class coal-fired technology would reduce CO2 emissions by 17%, Capturing waste heat would produce further increases in overall efficiency.

Click here to download the Report.