Anything as big and as promising as shale gas is bound to be complicated. This energy source has much to recommend it. To begin with, the U.S. has a lot of it, enough to meet current natural gas consumption for 35 years.

The increase in hydraulic fracturing, or fracking, the technique used to tap natural gas from shale, brought down the fuel’s price by 32 percent last year, to less than $3 per million Btu. Expanding the practice ― to New York State, for example, which now has a moratorium on it ― could help lessen American use of coal and oil to generate electricity and heat. That would reduce U.S. dependence on Mideast crude and lower greenhouse-gas emissions and acid rain.

Then there are the jobs that fracking has created, especially in parts of the U.S. hit hard by the economic slowdown. The number of people who work in the shale gas industry is expected to rise from 600,000 to 1.6 million by 2035, according to a study by IHS Global Insight for America’s Natural Gas Alliance, a trade group.

Yet, as the increasingly heated debate shows, the public still has well-founded concerns about the safety of fracking. None justify the level of anti-fracking rhetoric among some critics, who seem to think the energy they consume can be magically conjured without so much as the eyesore of a drilling platform. But some legitimate issues need to be addressed.

These are the main ones:

Earthquake activity

There is little doubt that the re-injection of fracking wastewater into wells, one method of disposing of it, has caused minor earthquakes in Arkansas, Ohio, Oklahoma and Texas. This sounds worse than it is. The temblors have been well below the magnitude necessary to cause damage. And it’s not so unusual for development projects ― dam building, mining, oil drilling ― to cause seismic activity.

Still, authorities need to ensure that operators offer a way to deal with fracking waste without causing regular quakes. The Environmental Protection Agency generally regulates underground fluid injections, but a 2005 loophole exempts those related to oil or gas production unless they involve diesel, which is sometimes contained in the mix used to fracture gas shale.

Congress should remove the loophole so the EPA can rule out earth-shaking methods of disposing of “flow-back” ― what returns to the surface after the water and fracking mix have been injected into shale. Companies may be able to eliminate tremors by mapping deep-rock formations in advance, then monitoring seismic activity as they re-inject wastewater, slowing or stopping if necessary.

Water pollution

A number of landowners have sued fracking operators for contaminating water supplies. Some lawsuits complain of fracking fluid or wastewater sloshing off trucks. Such cases can be mitigated by giving federal authorities the power to monitor such leaks. Other suits complain of seepage from poorly encased wells, which can also be minimized by rigorous standards and inspections.

The more provocative accusation is that the act of breaking up subterranean shale to free the natural gas within enables methane ― its main component ― and contaminants in the fracking mix to make their way up to aquifers. But shale deposits and aquifers are generally separated by thousands of feet of earth. Because aquifers sometimes contain methane naturally, communities may think fracking has changed water that was always gassy and was never checked before.

Greenhouse gas emissions

One of natural gas’s virtues is its greenhouse-gas footprint. Burning it produces only half as much carbon dioxide as coal, and significantly less than oil. Unfortunately, when natural gas is extracted from earth, significant quantities of methane leak directly into the atmosphere. And methane is an exceptionally potent greenhouse gas ― about 25 times as effective at trapping heat in the atmosphere as carbon dioxide.

Some studies argue that this leakage is especially great during fracking operations, compared with conventional extraction of natural gas. Methane escapes, for instance, during flow-back. In July the EPA proposed rules requiring that companies drilling new wells use available equipment to capture 95 percent of methane and make it available for sale.

The EPA estimates that these rules could reduce methane emissions by about 3.4 million tons a year. That’s the greenhouse-gas equivalent of 85 million tons of carbon dioxide, the amount released in a year by 18 average-sized coal-fired power plants. The agency should complete these rules ― and extend them to cover existing natural gas wells that are fracked again in the future.

Air quality

Neighbors of fracking operations have complained of headaches, rashes, nausea and respiratory infections. Some people suspect that such symptoms may stem from breathing air that has been fouled by fracking ― either by emissions of methane and other volatile organic compounds from wellheads or by pollutants evaporating from open-air pits where leftover drilling water is dumped.

Air measurements near fracking sites in Colorado and Texas have turned up above-normal levels of benzene and other carcinogens. Yet it is unknown whether the air is making people sick. The long-term national research that could provide the answer hasn’t been done. It should be, even as fracking operations continue. Meanwhile, the EPA should push fracking companies to not only capture emissions at the wellhead but also handle their wastewater to prevent toxic chemicals from evaporating.

These studies and remedial measures will entail costs, to companies and to state and federal regulators. (In proposing to spend $45 million in the 2013 federal budget on a research and development program to reduce the health, safety and environmental risks of fracking, the Obama administration seems to recognize the need for such expense.) And the effort might lead to a slowdown in the expansion of fracking.

To ensure that fracking realizes its promise, both the cost and the delay are worthwhile.

(Bloomberg)