A 'gas bridge' too far?

ClimateProgress

In his State of the Union Speech last week, President Obama returned to a familiar dual theme: trying to cut America’s carbon emissions while at the same time pursuing an “all of the above” energy strategy. A key part of Obama’s attempt to harmonise those two goals is natural gas.

Unfortunately, the latest science suggests that bridge may be on the verge of collapse.

First, the greenhouse gas emissions

Burning natural gas does indeed let off significantly less carbon dioxide than burning coal. But natural gas itself is mostly methane, an incredibly potent greenhouse gas that traps much more heat compared to an equivalent amount of CO2. And all along the production chain, from drilling to piping to transport, some of it will inevitably leak.

The Environmental Protection Agency has pegged natural gas leakage from production at 1.5 per cent. But the agency tends to rely on industry-provided numbers. A separate study by 15 scientists from institutions including Harvard, NOAA and Lawrence Berkeley National Lab looked at comprehensive atmospheric data and models, and concluded the leakage was at least 3 per cent. At 2.7 per cent or more, natural gas loses any advantage over coal in terms of its greenhouse effect.

That finding is backed up by other, more local studies by NOAA, which found a 4 per cent leakage rate from natural gas production around Denver, a 6-to-12 per cent rate from production in Colorado’s Uintah Basin, and a 17 per cent rate in the Los Angeles basin.

On top of all that, the fracking process consumes and pollutes enormous amounts of fresh water, which can leach from the wells into other groundwater supplies. That combines with the massive freshwater consumption by other fossil fuel energy sources, which in turn aggravates the water shortages brought on by climate change.

Second, the physical limits

A University of Texas study looked at a decade’s worth of information from the Barnett Shale – the formation near Fort Worth, Texas, with the longest history of natural gas fracking – and determined that production for most wells fell exponentially over that time. At this point, they’re on track to reach only 10 per cent of their potential – though the researchers did say well production could be “greatly improved” with better fracking methods, but that was a possibility only.

The problem boils down to pressure: as the amount of gas in the shale falls, there’s less pressure to push the remaining gas out. And since fracking involves splintering the shale to allow the gas to flow, the fall in pressure tends to interconnect across wells in the formation. The end result is that companies have to drill ever more wells just to keep the level of production constant over time. That drives up operational costs per unit of natural gas, and thus the price. Eventually, raw economics takes over, and the Energy Return On Investment – the amount of energy produced by the drilling verses the energy required to drill – falls too low. Drilling more is no longer worth it, and the wells tap out.

For fluids underground (ie. oil) the physics are essentially the same. Two other studies – one on oil from the Bakken Field under North Dakota and Montana, and the other on fossil fuel production across the globe over the last decade – found similarly dim prospects.

“The many trends of declining EROIs suggest that depletion and increased exploitation rates are trumping new technological developments,” said Charles A. S. Hall, a professor emeritus at the College of Environmental Science and Forestry, State University of New York, Syracuse.

In the end, renewable energy remains the only source of power that neither threatens the climate nor faces these sorts of brute physical limits.

Originally published on ClimateProgress. Reproduced with permission.