The juice from the six plants is collected and placed in an instrument called a refractometer, which measures the amount of light refracted in units called Brix. This Brix value is highly correlated to sugar content of the juice, Bean said, adding it is the sugar from sorghum that is converted into ethanol.

In 2009 studies, it was estimated that irrigated sweet sorghum produced 200 gallons of ethanol per acre, while the dryland sweet sorghum made about 80 gallons of ethanol per acre. Bean said this was assuming that 65 percent of the juice could be extracted from the sorghum.

He said it is possible that a commercial mill might approach 95 percent recovery of juice, which would greatly increase the potential amount of ethanol produced.

A byproduct of removing the juice from the sorghum is the plant material left over, Bean said. This material is called bagasse, and can be placed back on the field as crop residue, used as cattle feed or possibly burned at an ethanol plant as an additional energy source.

The final step to the harvest testing process, Bean said, is to take a sample from each 10 feet of row and run it through a limb chopper. The chopped material is weighed to get a fresh weight and then dried to get the dry weight, which will help determine the percent of moisture of each sample.

"By doing that, we can calculate how much either dry matter or fresh matter we had on a per-acre basis," Bean said. "By knowing that and also knowing our sugar content from our juice, we can calculate ethanol on a per-acre basis."

 

SKledbetter@ag.tamu.edu