Cattle stand around a huge pile of manure as a pen is cleaned out Aug. 28 at the JBS feed lot west of Greeley in Kersey, Colo. JBS, which runs two of the largest feed yards and the local slaughterhouse, is testing a new technology that heats the cattle excrement and turns it into energy.

GREELEY, COLO. ? The smell of manure hangs over Greeley as it has for half a century.

These days it’s more than just a potent reminder of the region’s agricultural roots and the hundreds of thousands of cattle raised on the city’s outskirts.

The stench smells like an opportunity.

Investors are lining up to support a planned clean energy park that eventually will convert some of the methane gas released from the manure piles into power for a cheese factory and other businesses. JBS, which runs two of the largest feed yards and the local slaughterhouse, is testing a new technology that heats the cattle excrement and turns it into energy.

“What once used to be a waste stream that was just a byproduct … they are now recognizing has value,” said Bruce Biggi, the economic development coordinator for the city of Greeley, which received an $82,000 grant from the governor’s energy office this year for the park.

The idea is to lure new business to the area with what Biggi likes to call its renewable natural gas — the endless supply of methane from cheap manure.

By reducing the amount of the potent greenhouse gas released into the air, the projects also potentially could turn cow dung into dollars, if a climate bill before Congress becomes law.

“Agriculture and agribusiness is what Greeley is all about,” Biggi said. “We needed to take that strong traditional economic base and … merge it with emerging renewable energy and technology.”

Waste may be the new energy crop in these parts. But elsewhere, communities are looking anew at power sources such as the sun and wind that may exist in their own backyards.

The shift is being driven partly by legislation in Congress that would reduce the gases linked to global warming.

The legislation, experts acknowledge, would do little to stem the heating up of the planet if other countries don’t take similar action.

Should President Barack Obama sign the bill, it would put a price on each ton of carbon dioxide released. That would drive up the cost of polluting fossil fuels such as oil and natural gas and lead to investment in cleaner sources of energy.

Getting into the game now — like JBS and the investors eyeing Greeley’s energy park are doing — could potentially reap profits: selling credits generated by reducing greenhouse gases now into the emissions-trading market the bill would create.

That market could prove lucrative for projects that reduce methane, which is 20 times more potent than carbon dioxide when it comes to trapping heat in the earth’s atmosphere.

The fear in Greeley, and elsewhere, is what else the legislation would change.

In the city and surrounding Weld County, the worry is it would raise energy and fertilizer costs for farmers. They need to pump water to irrigate their crops and rely on cheap manure — the same manure that will be tapped for energy — when high natural gas prices drive up the cost of fertilizer.

For the oil and gas industry, which produces more oil in Weld County than any other in the state, a shift to cleaner sources of energy could take away good-paying jobs. And it’s not clear whether all those will be replaced by the new green jobs that supporters are banking on.

“I can’t think of another place in the country like Weld County, where all the various interests are at play,” said John Christiansen, a spokesman for Anadarko Petroleum Corp., which produces oil and gas from 4,600 wells in the county. Many are on fields planted with feed corn, which also is being used to produce ethanol for gasoline locally.