Looking to out-green Hillary Clinton in New York, Bernie Sanders charged that Clinton’s position on fracking was at odds with voters.

New Yorkers ended the practice in the state in 2014, and Sanders called for a nationwide ban during an April 11 rally in Binghamton. Clinton, in contrast, remains on the side of the frackers, Sanders said on NBC’s Meet the Press, when he launched a multipart attack on Clinton’s positions on fracking, trade and campaign finance.

"Well, when you vote for virtually every trade agreement that has cost the workers of this country millions of jobs, when you support and continue to support fracking, despite the crisis that we have in terms of clean water," he said April 10, "and essentially, when you have a super PAC that is raising tens of millions of dollars from every special interest out there, including $15 million from Wall Street, the American people do not believe that that is the kind of president that we need to make the changes in America to protect the working families of this country."

Was Sanders telling the fracking truth? (We examined Clinton’s support for free trade in a separate fact-check.)

While Clinton’s past support of fracking is well documented, her current position leaves more wiggle room than Sanders’ statement suggests.

Shale promoted 'round the world

To refresh, fracking or hydraulic fracturing means producers are blasting pressurized water, sand and chemicals into shale rock miles underground to extract natural gas.

The Environmental Protection Agency considers shale gas to be clean energy. Some environmentalists, though, are doubtful that it’s that much better than coal or oil, given reports that fracking can cause methane leaks (a greenhouse gas that’s much more potent than carbon dioxide) and earthquakes and set water ablaze.

Clinton clearly supported the practice as secretary of state. Her special envoy for international energy affairs launched the Global Shale Gas Initiative encouraging other countries to explore shale as an energy source.

An in-depth investigation by progressive magazine Mother Jones said that Clinton’s support of fracking was "part of a broader push to fight climate change, boost global energy supply, and undercut the power of adversaries such as Russia that use their energy resources as a cudgel."

We found instances of Clinton and the State Department talking up fracking to Latin America, the European Union, Poland, Lithuania, Latvia, Bulgaria, Pakistan, China and India.

"The United States will promote the use of shale gas. Now, I know that in some places is controversial. But natural gas is the cleanest fossil fuel available for power generation today, and a number of countries in the Americas may have shale gas resources," Clinton said in a 2009 speech to the Inter-American Development Bank.

After Clinton left the State Department in 2013, she continued to support fracking but repeatedly called for "smart regulations" in speeches and in her book, Hard Choices.

Fracking with nuance in 2016

Compared with Sanders’ unequivocal opposition and the Republicans’ strong support, Clinton has a more complicated answer when it comes to fracking. Essentially, she supports it as long as there’s environmental oversight and no local opposition.

Here’s how Clinton detailed her position during the March 6 debate in Flint, Michigan:

"I don’t support it when any locality or any state is against it, No. 1. I don’t support it when the release of methane or contamination of water is present. I don’t support it — No. 3 — unless we can require that anybody who fracks has to tell us exactly what chemicals they are using.

So by the time we get through all of my conditions, I do not think there will be many places in America where fracking will continue to take place. And I think that’s the best approach, because right now, there are places where fracking is going on that are not sufficiently regulated."

("My answer is a lot shorter," responded Sanders. "No, I do not support fracking.")

Clinton spokesman Josh Schwerin referred us to Clinton’s plan "to address the fracking-related risks people are concerned about."

"This is particularly important given that the federal government doesn’t get to say where fracking occurs and where it doesn’t, but can put new safeguards in place," Schwerin said.

Katie Brown of Energy in Depth, the research and education arm of the Independent Petroleum Association of America, told PolitiFact that Sanders’ position to ban all fracking is outside the mainstream.

"Hillary Clinton, on the other hand, joins Democrats across the county such as Sen. Chuck Schumer, and California Gov. Jerry Brown, and Colorado Gov. John Hickenlooper (just to name a few), who have all touted strong regulations by the states and supported fracking for its environmental and economic benefits," Brown said.

Warren Gunnels, Sanders’ policy director, referred us to a Reuters article, in which supporters of fracking cast Clinton’s comments as campaign rhetoric and opponents urged her to cut the caveats and ban it outright.

But what exactly would Clinton’s caveats mean for frackers?

A portrait of regulated extraction

Clinton’s three conditions would uphold existing bans and add new ones to the mix. But they wouldn’t amount to a universal ban.

The first condition leaves local and state bans in place, such as those in Vermont, New York and a few dozen cities and counties across America.

Her second condition would add dozens of sites that have methane emissions or water contamination.

Natural gas is primarily methane, so we’ll assume Clinton is talking about "fugitive emissions" or leaks. Estimates for fugitive emissions, typically expressed as a percentage of the total production, vary widely. A round up of studies by watchdog blog Carbon Brief found estimates ranging from 0.6 to 9 percent (the threshold for being cleaner than coal is 3.2 percent).

Various industry and independent research has indicated that a good chunk of leaks come from a small number of "super-emitters" (roughly one in 25 facilities, according to a 2015 Colorado State University study). Clinton could ostensibly shut down these methane spewers, which include, for example, about 50 production sites in northern Texas and four lift wells in the Gulf Coast.

Water contamination is not systemic, according to a controversial 2015 EPA study, which nonetheless identified 151 cases of fracking fluid spills in 11 states from 2006 to 2012. Robert Howarth, a noted critic of fracking and biogeochemist at Cornell University, estimates at least 4 percent of production wells pollute water, but contends that the problem is widespread given the sheer number of wells.

Under Clinton’s condition, fracking could be banned in, for example, at least 25 counties in Pennsylvania and at least 12 counties in Colorado, if not in all 11 states with noted cases of spills.

Frackers are already meeting Clinton’s third condition, to an extent. At least 26 states have some rules on chemical disclosure on the books, though most allow frackers to protect "trade secrets," according to the American Chemical Society.

In addition, the Obama administration now requires drillers on federal and tribal lands to report the composition of their fracking fluid to FracFocus, an industry-backed registry of more than 100,000 wells across America. (Here’s an example.)

Environmentalists contend that these rules are not nearly enough. Howarth told PolitiFact that chemical additives are "a small part of the problem."

"The frack return fluids are full of really nasty materials in addition to the additives, and the precise nature of this toxic brew is seldom known," he said. "Clinton's focus on just the additives is misguided."

That being said, Clinton’s condition could ban fracking in Virginia and Missouri, two states with fracking activity but no disclosure rules in place at the time of this report.

Here’s a map that shows how Clinton’s conditions could affect fracking in America:

Our ruling

Sanders said that Clinton supported and continues "to support fracking."

As secretary of state, Clinton supported and promoted fracking around the world. As a 2016 candidate, her support comes with conditions such as local choice, stronger environmental regulation and chemicals.

Sanders’ claim is accurate but needs additional information. We rate it Mostly True.