Texas-Sized Sorghum to Fuel Future Ethanol Output
Date: 05-Oct-07
Country: US
Author: Karl Plume
Grain yield is not the goal with these crops. Scientists at Ceres and the Texas Agricultural Experiment Station (TAES) at Texas A&M University developed this sorghum to grow up to 20 feet tall and yield a massive amount of plant matter that the next generation of ethanol plants will convert into biofuel.
Most existing US ethanol plants produce ethanol from corn, but high corn costs and falling ethanol prices have squeezed margins. US ethanol production capacity currently stands at about 6.8 billion gallons a year.
"The target is 15 to 20 tons (of sorghum biomass) per acre, depending on geography and rainfall," Hamilton said.
That type of yield could produce up to 2,000 gallons of ethanol per acre of crop, about four times the yield of an average acre of corn. Sorghum also requires less water and only about a third of the fertilizer that corn needs.
"We've worked to come up with sorghum lines that are really not going to flower and set seeds. They're not going to put their photosynthetic energy into filling a grain head; they're going to put it into putting up more biomass," Hamilton said.
Farmers may be growing the massive sorghum as soon as 2009 or 2010 for the small number of cellulosic ethanol plants expected to be up and running on a commercial scale by then.
Farmers can use existing farm equipment, with only minor adjustments, to harvest the sorghum stalks and leaves which the biorefineries will then break down and convert into ethanol.
ETHANOL BEYOND THE CORN BELT
Normally, sorghum is grown for its grain in areas such as the US Plains where conditions are too dry to plant corn. Its hearty nature and its ability to grow to maturity within a single crop year makes it an attractive energy crop.
Perennial grasses like switchgrass usually do not begin yielding harvestable biomass until two years after planting so farmers may sow the giant sorghum variety to bridge gaps between switchgrass harvests, Ceres' Hamilton said.
"Think of sorghum as the sprinter and switchgrass as the long-distance runner. You'll get that nice sorghum yield that first year, but then after that your switchgrass will really be established," he said.
High costs initially slowed the expansion of cellulosic ethanol production, but new government grants and loan guarantees will help get the first wave of plants going.
Currently, experts estimate the cost of producing ethanol from cellulose at US$2.50 to $3.00 a gallon.
The US Department of Energy hopes that will drop to about US$1.10 a gallon by 2012 as feedstock costs decline along with the costs for enzymes needed in the ethanol making process.
Plants also were expected to become more efficient once the first generation of commercial-scale plants begin running.
By comparison, it currently costs about US$1.00 to $1.50 to produce a gallon of ethanol from corn grain.
Increasing the yield density of energy crops will also bring costs down, Hamilton said.
"Looking at the economics of a cellulosic biorefinery, about half of your cost is going to be feedstock at the refinery gate. Of that cost, harvest and transportation makes up the biggest fraction. By increasing yield density, you're impacting the biggest lever you have in the overall economics," he said.
