As a candidate, Barack Obama envisioned his administration passing a national low-carbon standard. The proposal would have required transportation fuel producers and importers to reduce carbon dioxide emissions from their fuels.

Nearly four years later, the standard does not exist.

In general terms, the proposal would require companies to meet a performance target for the amount of carbon dioxide released during the life of a fuel, from the oil fields to your car's gas tank.

Proponents use the phrase "carbon intensity" as shorthand for the rate of carbon dioxide released per unit of energy. It pertains to more than the fuel itself -- it also refers to carbon dioxide released in the process of producing and importing the fuel. So, technically, even a carbon-less energy source -- electricity as an example -- could have some carbon intensity associated with its production at the power plant.

A target would give companies the latitude to buy credits from companies that specialize in low-carbon biofuels. Companies could also lower their average carbon intensity by increasing the production of other kinds of fuel, such as hydrogen or natural gas.

Obama included the low-carbon standard as one of many ideas to wean the country off foreign oil, promote alternative energy and address climate change concerns.

Joseph Mendelson, policy director for climate and energy at the National Wildlife Federation, said the proposal is rooted in pragmatism: Even if markets for alternatives, such as biofuel or electric, continue to grow, conventional gasoline and diesel are likely to be part of our energy future.

"If you still have fuels around, you want them to be the least carbon polluting fuels possible," Mendelson said.

California and Oregon are the only states to have a low-carbon fuel standard, though most states in the Midwest and Northeast regions have studied the option in the last few years. (You can see a map here showing U.S. states and European countries that have a carbon standard, or are considering it.)

In his campaign promise, Obama said the standard would require fuel companies to reduce their carbon intensity 5 percent by 2015 and 10 percent by 2020.

In 2009, the U.S.House of Representatives, then controlled by Democrats, worked on major climate change legislation that included a national low-carbon fuel standard. But oil companies opposed it, and the final version passed the House without such a standard.

The Senate and House also considered individual bills on establishing a national low-carbon fuel standard in 2009, but both died in committee.

"It failed in large part because no one knew what it was or what it meant," said Dr. Daniel Sperling, director of the Institute of Transportation Studies at the University of California, Davis.

Two foundations, the William and Flora Hewlett Foundation and the Energy Foundation, have given grants to Sperling and other academics to research the proposal, giving special attention to its potential benefits and costs. Their findings, published in July 2012, are available on the group's website, the National Low Carbon Fuel Standard Project.

The White House Office of Science and Technology still mentions a low-carbon fuel standard as part of its environment and energy Website; the standard would be part of the White House plan to reduce greenhouse gas emissions by 80 percent by 2050. But we couldn't find any sign of the administration actively pushing the idea since the climate bill stalled in 2009.

We contacted the White House for any evidence that Obama advocated for the a low-carbon fuel standard, but never heard back.

Some groups say it's not Obama's fault that Congress won't pass legislation.

"(Obama) can't be held at fault for a dysfunctional Congress," said Heather Taylor, the director of a political arm for the pro-environmental reform group, the Natural Resources Defense Council. "He's shown if he could do something, he would."

One of the principles of our Obameter, though, is we rate promises for outcomes, not intentions. So with no low-carbon standard on the horizon, we rate this a Promise Broken.

Renewable fuels have lots of advantages, but when they're converted to energy, they can create carbon emissions that can harm the environment. By setting a standard, the Obama administration wants to make renewable fuels such as corn ethanol better for the environment.
 
During the campaign, Barack Obama said he would require nonpetroleum fuel suppliers to reduce carbon concentration of their products by 5 percent within five years and 10 percent within 10 years. Obama said he also wants a carbon standard for biofuels — energy made from corn, soy or other crops — to make sure they don't do more harm to the environment than good.
 
Before we delve into Obama's promise, a little background.
 
Measuring the overall carbon emissions of biofuels is tricky. While corn ethanol, for example, is cleaner burning than traditional petroleum, some people argue that the energy used to grow, water, harvest and process the corn into ethanol outweighs ethanol's benefits. And there's another problem: As the demand for biofuels increases, environmentally sensitive lands such as rainforests in Indonesia are being used to grow more of the crops needed for fuel production. When forests are cut down and turned into farmland, carbon is released into the atmosphere.
 
Scientists have attempted to quantify these auxiliary emissions in recent years, but with little success. Nevertheless, some states have tried to implement their own rules. In the spring of 2009, California adopted a new regulation that required all fuel used in transportation to have a 10 percent greenhouse gas savings by 2020.
 
Taking its cues from California, the Environmental Protection Agency announced on May 26, 2009, that it was planning to increase the Renewable Fuel Standard, an existing mandate that requires gasoline to be blended with ethanol or biodiesel, from 9 billion gallons of of blended fuel to 36 billion gallons in by 2022. (With the passage of the Energy Independence and Security Act of 2007, EPA is required to to make these changes.)
 
The administration also said that it would be using that standard to set greenhouse gas limits on these renewable fuels. So, for example, the regulation under discussion would require biofuels have a minimum 20 percent reduction in greenhouse gas emissions. Advanced and cellulosic biofuels — fuel made from left over biomass such as wood chips — would need to have a 50 or 60 percent reduction in greenhouse gas emissions, respectively.
 
"For the first time in a regulatory program, lifecycle analysis of GHG emissions is being utilized to establish those fuels that qualify for the different renewable fuel standards," the announcement said. "Based on our lifecycle analysis, we believe that the expanded use of renewable fuels would provide significant reductions in GHG emissions over time, such as carbon dioxide."
 
Obama is still a long way from fulfilling his promise, however. Farming interests threw a wrench in his plan during debate this summer over a bill to limit carbon emissions. To get the industry's support, House leaders agreed to insert language into the bill that would ensure widespread scientific agreement linking biofuels to global land-use changes before the EPA could move forward with its new greenhouse gas rules. And absent from the proposed regulations is Obama's original promise that fuel producers would be required to reduce carbon 5 percent within five years and 10 percent within 10 years.
 
With the regulations a long way from being put on the books — it's a process that could take years and stacks of comments from the public — we're moving this one to In the Works.