NATCHEZ &8212; Although all the details of the plant&8217;s design have not yet been determined, a Rentech official said the company&8217;s proposed Natchez facility will have environmental controls in place to prevent mercury, sulfur compounds and the like from leaking into the environment.

Last week, the Colorado-based company announced that pending approval of state and federal incentives, it would build a 200-job plant near the Natchez-Adams Port by fall 2010. The plant would gasify coal, converting it to a clear diesel fuel, generating a byproduct of fertilizer. It, along with a planned plant in East Dubuque, Ill., would be Rentech&8217;s first production facilities.

According to the Environmental Protection Agency, coal gasification can produce sulfur-containing acid gases that may contain carbonyl sulfide, carbon disulfide, hydrogen sulfide and sulfur-containing organic compounds known as mercaptans. The latter has few health effects, if any, according to the EPA.

Information from the National Institutes of Health cited studies showing the other sulfur compounds can cause symptoms ranging from eye, skin and digestive and respiratory irritation; impaired psychomotor functioning; higher risk of cardiovascular disease and miscarriages; and, in severe cases, sudden unconsciousness and death. None of the substances are shown to cause cancer.

But such possible effects must be put into perspective, said John Grasser, public affairs director for the U.S. Department of Energy.

&8220;This is a very clean technology,&8221; he said of coal gasification. &8220;Emissions are only a fraction of conventional (coal combustion) plants.&8221;

Grasser cited studies showing that sulfur dioxide emissions have been measured at .03 pounds per million BTU for a coal gasification plant versus 1.5 pounds per million for a conventional coal-burning plant.

Indeed, modern coal gasification plants&8217; processes include the conversion of sulfur compounds back to elemental sulfur &8212; which Rentech Development Corp. President Richard Sheppard said would be the case at the planned Natchez plant.

&8220;The sulfur will come out as a solid and will be sold as a product&8221; to other industries, Sheppard said.

Brendan Bell, an energy analyst for the Sierra Club in Washington, D.C., said mercury can also be a concern when it comes to gasification.

&8220;Mercury contamination &8230; can be hazardous, especially for pregnant women. It&8217;s also somewhat of a water issue, because (mercury) gets into fish&8221; and can cause contamination if consumed, Bell said.

Mercury isn&8217;t shown to cause cancer but can cause respiratory and other problems if inhaled and can also cause psychotic reactions and kidney problems.

But, Sheppard said, Rentech has a plan in place to keep any resulting mercury out of the environment &8212; in this case, using activated carbon beds to trap the element.

Other environmental safeguards the plant will put in place include the careful checking of cooling water before it&8217;s discharged to a water treatment facility and carefully stacking coal and using other techniques to reduce the amount of dust given off by the coal the plant will use.

In addition, the plant won&8217;t give off &8220;anything like slurry that would need to be landfilled,&8221; Sheppard said.

Like Grasser, Sheppard noted the coal gasification of today is a far cry from the polluting coal burning plants of yesteryear.

&8220;This is a coal gasification plant, not a combustion (plant),&8221; Sheppard said.