And because the elevators were designed to work with petroleumbased-hydraulic fluids, the replacement had to match its performance almost exactly. The National Center for Agricultural Utilization Research, an ARS div., determined soy oil as its best option.

"We had been working with hydraulic fluids for a while, but not for elevators," said Sevim Erhan, research leader at the Food and Industrial Oil Research Unit of ARS in Peoria, Ill. "But after researching properties of petroleum-based hydraulic fluid, we were confident we could develop a comparable soy hydraulic fluid."

Before it would work, Soybean oil had to be mixed with antioxidants to improve stability and prevent thickening at high temperatures. Pour point depressants were also added to prevent gelling during cold spells.

After two years of use at the Statue of Liberty, the soy-oil lubricating properties have shown to be comparable, if not better than petroleum-based hydraulic fluids, says Erhan. "It also has a much higher flash point, so the risk of fire is reduced."

Jack Stover, owner of Agri-Lube Inc., Defiance Ohio, which produces the fluid, says the most important advantages of soy oil over petroleum oil are its environmental friendliness and safety.

"Hydraulic fluid typically leaks, leaving a puddle at the bottom of the shaft, causing environmental and fire concerns," Stover says. "But soy oil readily degrades, there is little harm to the environment."

Agri-Lube is setting licensing rights with the USDA for commercial production of the soy hydraulic fluid. So, Stover couldn't disclose the oil's composition, but did say that it has a bright future in hydraulic applications. "The nation's park services could use it in snowmobiles and lawn mowers, while other government agencies, private parks, and universities could use it in their hydraulic systems," Stover says. "Some Ivy League and Big Ten universities, for example, will be using soy elevator grease in elevators this year."