Natural Gas: Promise or Peril?

(This blog is based on a talk I gave last week at the Rethink Methane symposium in Sacramento, California.)

A couple of years ago, many people in the environmental community were bullish on natural gas. Methane burns cleaner than coal, producing only about half the carbon dioxide, and almost no sulfur dioxide or mercury. When NRDC moved to clean up dirty diesel buses in New York City in the 1990s, natural gas was the answer.

But then fracking entered the scene. Fracking can contaminate drinking water, and use up limited water supplies. As NRDC studied fracking and its effects on rural communities more, we saw many reasons for concern. We created a Community Fracking Defense team. We supported the ban on fracking in New York State.

We also began to recognize that methane isn't so great from a climate perspective, either. It's cleaner when burned, but if the methane leaks into the atmosphere, it is a powerful climate pollutant--at least 25 times more potent than carbon dioxide in the long run, and more than 100 times more powerful over a 20-year period.

So while natural gas can offer some environmental benefits, it can also present major environmental challenges. If we want to capitalize on the promise of methane and avoid its perils, we have to pay close attention to the details of how methane is produced and how it is used.

Capturing Methane Waste

The first place to look for promise in methane is to capture it where it leaks. Methane can get into the atmosphere when it leaks from oil and gas drilling operations. It can get into the air when it leaks from waste ponds on industrial livestock and dairy farms, or rises up from organic matter decomposing in landfills.

In these instances, methane is an unwanted byproduct. It's a source of pollution instead of a resource. We're letting it go to waste, where it does harm instead good.

So if we can capture those leaks, is that a solid win?

Well, it's complicated.

The Pitfalls of Incentives

We should definitely capture any leaking methane from the fossil natural gas system, but let's do so without creating incentives for more fossil natural gas, since in the next decades we will need to get off fossil fuels entirely if we are to preserve our climate's stability.

How about the biological methane being emitted from landfills and manure lagoons? Certainly we should capture all of that, but in ways that do not create any perverse incentives. Let's ensure that we are reducing pollution and creating clean energy, which will substitute for dirty energy.

Consider landfill natural gas. The only reason methane comes out of landfills is because there's organic matter in there. If food waste were a country, it would be the third largest greenhouse gas emitter in the world. So where methane is being produced at a landfill, by all means, let's capture it.

Out of the more than 1,000 landfills with significant potential for captured gas, only about 600 do it. And they mostly generate power on-site, rather than convert it to high-quality methane. This understates the number of facilities from which methane is escaping, such as smaller or older landfills, if more cost-effective technologies were available for collecting it.

While encouraging this capture we need to be careful not to create incentives for more methane from landfills. Moving forward, we need to be composting organic matter so it can be made into useful nutrients instead of landfilled.

The same goes for capturing methane from large dairy farms. We've barely started in this sector. Right now, most animal waste is collected in open-air lagoons and sprayed or poured onto fields. This often pollutes ground and surface water, stinks up nearby communities, causes health problems and contributes to climate change.

Out of the more than 12,000 significant animal feeding operations with manure lagoons, it's estimated that fewer than 250 capture biogas. So there is clearly a huge opportunity here to reduce pollution and help create rural income and jobs.

But again, we need policies that encourage capturing this methane without encouraging more consolidation of animal farms. We also need to be sure that we use technology that also captures NOx, a major air pollutant, as well as the nutrients in the waste to make them available back in the farming cycle.

There is also the chance to capture methane from municipal sewage plants. Here, we are doing a bit better, but out of close to 5,000 candidate sewage plants, about a quarter of capture methane. This is already a highly regulated area, so quick acceleration here could be possible.

Finally, let's think about collecting agricultural waste and capturing the energy embedded not just animal manure, but crop wastes. Here, the complexities are even greater, since careless incentives for energy crops can lead to competition with food crops, or use organic matter that is needed to restore soil health.

Moreover, anaerobic digestion for intermittent wastes such as crop residue is challenging. And lifecycle analysis shows that just because waste is biological does not mean it's carbon neutral - NRDC created a "Forests Not Fuel" campaign to ensure that whole trees are not used for bioenergy because of the enormous carbon deficit created by cutting them. But certainly, there are some non-animal agricultural wastes that offer promise.

So, while there are a few caveats, there are clearly opportunities to develop policies and technologies that will encourage greater capture of waste methane and take advantage of this resource.

Some of this gas will likely seem too expensive in comparison to alternatives today. But look at other renewable energy technologies. Once we focus on them, their costs plunge. Solar electricity costs have decreased about 80% in the last five years and wind costs have been cut in half. With the right policies and focus, technologies to capture waste biological natural gas could be made more cost-effective.

If we focus on getting natural gas from truly waste sources -especially those that are currently polluting methane into the atmosphere - without creating improper side effects, then we can capitalize on the promise of methane.

Best Uses of Captured Methane Waste

There is another side to the equation, however - what we do with the gas.

Right now, the methane that is captured is mostly used to create electricity and burned on-site. This might not be the best use. Just as it is a waste to let a clean fuel source leak into the atmosphere where it becomes a pollutant, it is also perhaps a waste - albeit a lesser one - if we use biological methane in place of even cleaner electricity sources.

We have a number of options for clean electricity that are ramping up in scale and dropping in price - onshore and offshore wind; concentrated and distributed solar; geothermal and other technologies.

We also have a good option for clean light duty transportation - electric vehicles, especially those running of clean electricity.

We don't have as many options for heavy-duty trucks or planes or ships. We need a high-density fuel and this is where methane waste might be particularly useful.

Using recaptured methane to replace fossil diesel fuel can make a big difference, substituting for perhaps a third of the diesel used in heavy-duty vehicles. If this same natural gas is used for electricity or home use, however, the environmental benefit will be relatively insignificant.

Conclusion

Methane might have a simple chemical formula, but it's not a simple issue. All sources of bioenergy are not created equal--the feedstock itself, the way it is produced, and what we do with it - all this matters. It's critical to get this right sooner rather than later.

About the Authors

Peter Lehner

Former Executive Director

Join Us

When you sign up you'll become a member of NRDC's Activist Network. We will keep you informed with the latest alerts and progress reports.