A fertilizer factory and part-time hydrogen power plant proposed outside Tupman would produce less air pollution than had been anticipated under an earlier, electricity-only version of the project, according to paperwork filed this month with the state.

Although it still does not sit well with farmers and other neighbors, the $4 billion Hydrogen Energy California project is expected to produce 164 tons a year of nitrogen oxide -- 16 percent less of the smog contributing gas than state officials said would have been produced under the project's earlier plans.

SCS Energy, the Massachusetts company behind the new proposal, also estimated that the project would emit 32 percent less carbon monoxide (275 tons a year), 40 percent less volatile organic compound (35 tons) and 23 percent less silicon dioxide (29 tons). The project is expected to produce roughly the same amount of fine particulates.

SCS purchased the project last year from oil giant BP and mineral company Rio Tinto, both of which bowed out after determining that their proposal did not make financial sense. SCS, in turn, changed the focus to producing urea and other fertilizers used in the Central Valley, as well as generating about 300 megawatts of power during times of peak demand, when electricity costs the most.

HECA, as the 470-acre project is known, aims to accomplish a number of government-supported goals, including creating up to 200 permanent jobs, testing clean coal technology, assisting nearby oil production and burying large quantities of the greenhouse gas carbon dioxide. HECA has received a $408 million grant from the U.S. Department of Energy, largely because of the project's ability to demonstrate cleaner energy technology.

Los Angeles-based Occidential Petroleum Corp., operator of the nearby Elk Hills oil field, hopes to buy byproduct carbon dioxide from HECA and inject it underground as a way of promoting oil production. Oxy expects to store the gas -- some 3 million tons a year of it -- in the area's subterranean rock formations indefinitely rather than let the greenhouse gas vent into the atmosphere.

Local objections

Neighbors maintain that the project is incompatible with surrounding land uses, which include dairy operations, farming, an equestrian center and residences. Apart from their fears about the traffic it would bring the area, neighbors contend that HECA would produce less pollution if it ran on natural gas instead of coal and petroleum coke.

"We're in jeopardy -- right next to it, and it's not proven," said farmer Chris Romanini, a member of Concerned Neighbors of HECA, which wants the project moved away from farms, houses and businesses.

Shafter almond farmer Tom Franz, president of a valleywide air quality and environmental justice advocacy group, called the Association of Irritated Residents, said HECA's estimated nitrogen oxide emissions are still more than twice those of natural gas plants producing about the same amount of electricity.

"We're very concerned about NOx emissions here in the valley. We could care less about CO2," he said. CO2 is carbon dioxide.

"Why do they have to experiment with this type of power plant in our backyard when we have such terrible air quality?"

HECA officials told The Californian last month that they continue to seek financing for the project. They noted that one of the bigger engineering hurdles left is figuring out how to switch back and forth easily between fertilizer production and power generation.

If the project is approved by the California Energy Commission and the state Division of Oil, Gas and Geothermal Resources, HECA could begin construction in spring 2013 and become operational in fall 2017.