Natural gas: Is it a bridge or roadblock?

Natural gas: Is it a bridge or roadblock?
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Is natural gas a bridge or a roadblock to a clean energy future? That’s a vital question now that roughly half of Democratic presidential candidates support a ban on fracking, which is used to produce two-thirds of U.S. natural gas.

Even candidates who oppose a ban agree that the United States should aim for net-zero emissions overall by 2050 or sooner. 

So far, the pursuit of net-zero has been far too slow, but natural gas has played a helpful role. American emissions of climate-warming gases have fallen roughly 15 percent from their peak. Replacing coal with natural gas for electricity contributed about a third of that reduction. 

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Whether natural gas helps or hurts the quest for further reductions will depend on two things: How we get it and how we use it.

On the supply side, leaking just a few percent of natural gas can negate much of the benefits of gas versus coal. That’s because natural gas is mostly methane, a gas that is roughly 30 times as potent as carbon dioxide. 

Many oil and gas companies are already taking rigorous steps to avoid leaks, since they waste valuable fuel into the air. But the Trump administration is moving to roll back regulations on leaks. 

Beyond curbing leaks, there are opportunities to obtain gas more sustainably. Methane could be captured from landfills and wastewater treatment plants and used for energy. Biogas could be made from food scraps and animal waste. And “power-to-gas” technologies could use clean electricity to produce hydrogen and then convert it into methane for fuel. 

All of these options would give us a cleaner supply of natural gas. But how gas is used is just as important as how it is obtained, research by my group at Rice University has shown. 

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Using natural gas instead of coal for electricity slashes emissions, assuming methane leaks are controlled. So does replacing fuel oil furnaces with natural gas ones. 

By contrast, natural gas cars and buses emit nearly as much climate-warming gases as gasoline and diesel ones, once methane leaks are included. Natural gas fueling infrastructure is a bridge to nowhere, when we should be investing in charging infrastructure for cleaner electric vehicles. Unfortunately, legislation recently introduced in the House, H.R. 5089, would subsidize the wasteful use of natural gas in vehicles.   

Even for electricity and heating, care is needed to use natural gas as a bridge rather than a roadblock to cleaner options. Flexible natural gas electricity can help balance the output of variable solar and wind power as they scale up, letting coal plants close without adding enormous amounts of batteries. Eventually, though, we’ll need alternative complements to solar and wind, or gas plants that can capture their own emissions. NET Power is piloting new technologies that would do just that.

For heating, natural gas furnaces are cleaner than heating oil furnaces, but not as clean as electric heat pumps once electricity gets cleaner. But electric heat pumps struggle in the coldest weather. Hybrid heating systems could use gas to reduce peak electricity demand on the coldest days and electricity at other times. 

Policy will be pivotal to ensuring that natural gas is obtained and used in ways that make it a bridge to cleaner energy. Banning leaks and putting prices on methane and carbon dioxide emissions could ensure that natural gas is obtained and used more responsibly.

Research will be needed to develop new technologies for power-to-gas conversions, carbon capture, and hybrid heating systems. And by slashing the most wasteful uses of natural gas, biogas and other clean supply can satisfy the remaining demand.

Even with all of this, natural gas should be seen as a bridge, not a destination. A net-zero future will require slashing emissions from all fossil fuels and offsetting the emissions that remain. Still, sensible choices in how natural gas is obtained and used can clear away some of the roadblocks to cleaner energy.

Daniel Cohan is an associate professor in the Department of Civil and Environmental Engineering at Rice University.