Vice President Joe Biden and Rep. Paul Ryan squared off Thursday night in the only vice presidential debate of 2012, offering a lively and contentious clash that touched on a variety of domestic and foreign policy issues. Both sides claimed victory afterward, and many public opinion polls showed mixed results.

The VP debate did have one clear loser, though: the environment. Moderator Martha Raddatz of ABC News never asked about environmental issues, and neither candidate had much incentive to broach the subject. Halfway through the 2012 debate season, there still hasn't been a single mention of climate change — despite President Obama's recent assessment that it's "one of the biggest issues of this generation."

While much of the debate centered on Libya, Afghanistan, health care and abortion, it wasn't completely devoid of environmental discussion. Perhaps the most memorable line came from Ryan, Mitt Romney's running mate, who accused Biden of overseeing $90 billion in "green pork" as part of the 2009 stimulus bill. Here's the quote:

"Look at just the $90 billion in stimulus. The vice president was in charge of overseeing this. $90 billion in green pork to campaign contributors and special interest groups. There are just at the Department of Energy over 100 criminal investigations that have been launched ..."

The $90 billion statistic was also used in last week's debate by Romney, who implied the DOE loan-guarantee program had invested $90 billion in green energy companies, half of which are now bankrupt. Fact-checkers pounced on that claim, since the DOE actually awarded about $16 billion in loan guarantees to more than 30 clean-energy companies, three of which are now out of business.

Ryan didn't repeat that mistake, referring more broadly to "$90 billion in stimulus," which includes things like weatherization, energy-efficiency upgrades and public transit projects as well as clean-energy loans. But according to the Associated Press' fact checkers, his statement about "green pork" still wasn't entirely accurate:

"Dismissing an entire package of energy stimulus grants and loans as 'green pork' ignores the help that was given to people to make their homes more energy efficient, grants to public entities constructing high speed rail lines and tax credits to manufacturers to install equipment fostering cleaner energy."

The AP acknowledges the "notable failed investments" — Solyndra was the elephant in the room for this part of the debate, even though neither candidate mentioned the company by name — but it warns that "Ryan's claim made it sound like every penny went down the drain." On the contrary, the AP adds, "economists are nearly universal in saying Obama's [stimulus] helped create both public-sector and private-sector jobs, even if they fell short of what sponsors had hoped." The nonpartisan Congressional Budget Office, for one, estimates the stimulus saved or created 3 million jobs.

While Biden often accused Ryan of bending the truth — sometimes by calling his claims "malarkey," other times by flashing a grin — he didn't bother questioning the veracity of Ryan's green pork comment. Instead, he first pointed out that a yearlong congressional inquiry into Solyndra "found no evidence of cronyism," a response to Ryan's claim that stimulus money went to donors and special interests. Biden then tried to paint Ryan as a hypocrite, noting the Wisconsin congressman has asked the Obama administration for stimulus funds. Here's the exchange:

Biden: "And I love my friend here. I — I'm not allowed to show letters but go on our website, he sent me two letters saying, 'By the way, can you send me some stimulus money for companies here in the state of Wisconsin?' We sent millions of dollars."
Raddatz: "You did ask for stimulus money, correct?"
Ryan: "On two occasions we — we — we advocated for constituents who were applying for grants. That's what we do. We do that for all constituents who are ..."
Biden: "I love that. I love that. This was such a bad program and he writes me a letter saying — writes the Department of Energy a letter saying, 'The reason we need this stimulus, it will create growth and jobs.' His words. And now he's sitting here looking at me."

Ryan actually sent at least four letters to Energy Secretary Steven Chu in late 2009 — see PDF copies here — in which he sought stimulus funds for various energy-conservation efforts in Wisconsin. After acknowledging this during Thursday's debate, however, he then went back on the attack, asking Biden "Was it a good idea to spend taxpayer dollars on electric cars in Finland, or on windmills in China?"

While Fisker electric cars are built in Finland, and some wind-turbine parts do come from China, the Tampa Bay Times' PolitiFact rated Ryan's claim "mostly false":

"In fact, the program that provided loan guarantees for the Fisker cars was not part of the stimulus — and the money went toward engineering and design in the United States. As for the windmills in China, it's true that a small number of windmills and components to build them came from China. But the statement greatly exaggerates China’s role in the overall use of stimulus money."

Biden countered that stimulus spending on green jobs was a good idea, arguing that "4 percent of those green jobs ... went under, didn't work. It's a better batting average than investment bankers have." Ryan started to respond, but Raddatz cut off the discussion, asserting that "we've gone over this quite enough."

The two remaining presidential debates will take place Oct. 16 in Hempstead, N.Y., and Oct. 22 in Boca Raton, Fla. For a more in-depth look at Thursday night's VP debate, read the full transcript or watch the video below:

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Russell McLendon ( @russmclendon ) writes about humans and other wildlife.

Biden vs. Ryan: What is 'green pork'?
Aside from a brief clash over clean energy, the only vice presidential debate of 2012 featured very little discussion of environmental issues.