U.S. government researchers say they\'ve developed an inexpensive way to grade the ethanol potential of perennial grasses right at a biorefinery\'s loading dock.Scientists with the U.S. Department of Agriculture say the process involves the first use of near-infrared sensing to measure 20 components in switchgrass biomass to determine its potential value to biorefiners, a USDA release said Thursday.These measurements include cell wall sugars, soluble sugars and lignin, and can reveal 13 traits of the sampled material, including the efficiency of the conversion from sugars to ethanol.The NIRS method can be used to estimate what the total potential yield of ethanol or other biofuels would be if all sugars in the plant were converted.Compared to the $300 to $2,000 cost per sample being analyzed using existing conventional methods, the NIRS process can estimate ethanol yields of switchgrass at about $5 a sample, the USDA said.The method can also be used to find methods of growing grasses for the highest ethanol yields, the department said.