For those who blame auto makers for a rise in greenhouse gas emissions, it may be worth noting a new report by the United Nations Food and Agriculture Organization that says the livestock sector generates 18% more harmful gases, as measured in carbon dioxide equivalent, than the vehicle transport segment and also is a major source of land and water degradation.

“Livestock are one of the most significant contributors to today’s most serious environmental problems,” Henning Steinfeld, author of the report, is quoted as saying. “Urgent action is required to remedy the situation.”

Livestock production generates 65% of human-related nitrous oxide, which has 296 times the global warming potential of CO2, most of it from manure, the report says. It accounts for 37% of all human-induced methane, 23 times as warming as CO2, as well as 64% of ammonia, which contributes to acid rain.

This does not let auto makers off the hook, however, and they know it.

Recent record high fuel prices, along with a growing alarm over the role vehicles play in global climate change, has prompted major car makers and government policy makers the world over to focus their mutual attention on a variety of alternatives to crude oil.

Automotive engineers are turning to varied solutions to serve regional needs that include vehicles powered by hybrid-electric, biodiesel, hydrogen-internal combustion, liquefied petroleum and compressed natural gas and bioethanol-fuel technologies.

The loudest clamor in the U.S. is for flex-fuel vehicles (FFVs) that can run on a combination of gasoline, or diesel, and ethanol made from corn, sugarcane and other natural plant materials.

This technology is driven by the need for an independent renewable resource and also because biofuels typically can be used much the same way as conventional fossil fuels.

For auto makers, it’s the cheapest way to begin to address alternative fuels, as most vehicles already can run on a 15% ethanol/gasoline blend, while purpose-built FFVs adapt automatically to fuels ranging from pure gasoline or diesel to an E85 (85% ethanol) blend.

GM is throwing considerable resources into producing FFVs as a short- to medium-term solution to what Chairman Rick Wagoner says is “an increasingly uncertain energy future on a global basis.”

In an address at the recent Los Angeles auto show, Wagoner said GM now has more than 2 million E85 vehicles on the road, with plans to expand production.

“At GM, we believe that the biofuel with the greatest potential to displace petroleum-based fuels in the U.S. is ethanol…and so we have made a major commitment here to vehicles that run on E85 ethanol,” he said.

“In a meeting with President Bush earlier this month (November), Tom LaSorda (Chrysler Group), Alan Mulally (Ford) and I announced that America’s domestic auto companies were prepared to make fully half of our annual vehicle production biofuel capable by 2012…provided there is ample availability and distribution of E85, as part of an overall national energy strategy.”

No one can argue that’s a good start. At least until the cows come home.