Sugarcane retooled to make biofuels

Sugarcane retooled to make biofuels

Researcher hopes to release second-generation bioenergy sugarcane plants in two years.

IN his "State of the Union" address in 2006, then-President George W. Bush suggested that scientists use switchgrass to produce an ecologically friendly fuel: cellulosic ethanol produced from natural materials.

Some took his comments very seriously, including a Texas A&M AgriLife Research scientist who had been working on such a project for years. Today, Dr. Jorge da Silva predicts that he will release such a product from his laboratory within two years.

Da Silva isn't using switchgrass, however, opting instead for sugarcane, which he said better lends itself to being redesigned and re-engineered to help fulfill Bush's dream of "providing 30% of our transportation fuel by 2030."

"Unlike corn or even switchgrass, sugarcane is unique in that it can be crossed with different species, including sorghum, to create new plant varieties with favorable traits that are competitive with corn in producing biofuels," da Silva said.

Using genetic markers, he transfers favorable genetic traits from a variety of plant sources to sugarcane to make new plant material called wide-hybridization, according to Texas A&M.

These new plant varieties would make up the world's second generation of bioenergy plants, which have the potential to eventually replace corn and even sugarcane in the production of ethanol, da Silva said.

"Those were the first-generation plants: corn and sugarcane," he said. "The starch from corn and the sugar from sugarcane were converted to ethanol, but both are food plants that, when used to make fuel, create a conflict with their ability to produce food."

The biomass (stalks and leaves) of da Silva's plants — which are the result of conventional breeding and selecting methods — are mixed with enzymes to create ethanol, Texas A&M said.

"What we end up with is a sugarcane-based plant with biomass that is at least nine times more efficient in producing ethanol than corn biomass," da Silva said.

Creating new fuel-producing material from sugarcane has challenged da Silva throughout his 12-year career with Texas AgriLife Research. Sugarcane's genetic makeup, developed naturally over thousands of years, can be revamped to better serve growers and consumers, but not overnight, he said.

A major challenge in breeding sugarcane is its complex genetic composition, da Silva said. Some grasses, especially sugarcane, have many more genes and chromosomes than even human beings. While humans have two copies of each gene, sugarcane has 10 copies of each gene.

"This genetic complexity creates many variables that are not under our control, making it difficult to predict agronomic performance — how it will yield and react in the field," da Silva said.

Any major genetic improvements to sugarcane for biofuels must include an ability to grow outside its comfort zone.

Until now, corn has been widely used as a feedstock for biofuels in the U.S. because massive corn acreage is already in place and because corn grows well in temperate zones, he said. Sugarcane, however, is a tropical and subtropical plant.

"We want it to be able to grow outside the tropics like corn is, to be cold tolerant, drought tolerant and resistant to diseases and insects. It's called pyramiding — assembling and stacking from different sources favorable genes that control traits," da Silva said.

Working in da Silva's favor in meeting the challenges, he said, is Texas A&M University's efficient plant replication method that rids plants of disease.

One of the techniques used in da Silva's lab is a process called micropropagation. Plants to be evaluated can be reproduced much more quickly than through the natural seed-to-plant method, and the resulting clonal plant material is free of any disease its ancestors may have carried.

"Producing these plants via tissue culture is faster and ensures that we're not spreading plant diseases as these new plants go to the field. And, we use bioreactors ... to speed up the multiplying process using less labor and less laboratory space," he said.

Micropropagation is a highly reliable method that allows da Silva to plant bigger research field plots at more sites to gather data on a larger scale.

His crosses and selections have been narrowed down from hundreds of thousands of possibilities to what he calls elite lines — those hybrid plants with the favorable traits needed to more efficiently produce biofuels. The elite lines are now being tested in various locations throughout Texas.

While da Silva expects to produce and have a half-dozen varieties ready for release in about two years, it's a dynamic process that will likely never end.

"Plant varieties will always be improved upon because there are always new challenges to plant production," he said. "We're always seeing new diseases, new pests, the industry changes, economics change — it will always be a dynamic, evolving process."

As da Silva develops the plant material for efficient conversion to biofuels, facilities to process the varieties are in the pilot stage of development.

"That's the other side of this new technology," he said. "When those facilities are ready to produce fuel, we need to be ready with the plant material."

Volume:85 Issue:36

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