Switchgrass and Drop-In Fuels

Coming to a prairie (or pump) near you

What is it?

 

A native of the American prairie for hundreds of years, switchgrass is sometimes called tall prairie grass, tall panic grass, wild redtop, blackbent, or thatchgrass.  Its wealth of seeds and thick cover attract song birds, quail, pheasant, and other wildlife, while its deep roots – almost as deep as the plant is tall – help prevent soil erosion.  To bioenergy scientists, it is an unusually promising source of biomass.  

 

Why is it of interest?

Versatile and long-lived, switchgrass has evolved to withstand extremes of temperature, wind, and drought.  It generally can grows between 4 feet to 6 feet high, but can reach heights of 13 feet, which adds up to a lot of biomass.  Even on an acre of marginal land, lowland switchgrass has been known to produce six to eight tons of biomass in one harvest.

Where does it grow?

In much of North American, especially prairies in the Midwest.

Why does it matter?

Besides being very productive, switchgrass grows well with relatively little water, lime or fertilizer. Once planted, it can also produce biomass for up to 15 to 20 years without replanting.

What’s next?

Scientists are working on a crude bio-oil from switchgrass that can be transported directly to a refinery.

Who’s working on it?

This list includes the Department of Energy and its Oakridge National Laboratory, the Lousiana State University AgCenter, the University of California at Berkeley, the University of Illinois at Urbana-Champaign, and researchers in Tennessee, Virginia, Texas, and China.

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New Integrated Process for Drop-In Fuels

What is it?

Separate is good; integrated is better. Researchers at UC Berkeley have found a way to put a new spin on some old chemistry, making renewable drop-in fuels more efficiently.

How does it work?

Grow the bacterium Clostridium acetobutylicum on sugar and it makes a dilute mixture of acetone, butanol, and ethanol. This diesel-like mix was derived from the products of a bacterial fermentation discovered nearly 100 years ago. Normally, you would have to put in a lot of energy and distill the products, which can be blended with gasoline up to 16 percent. Alternatively, you could extract the products with glycerol butyrate and pass them over a palladium catalyst to make longer chain hydrocarbons and alcohols.

What does it matter?

The retooled process produces a mix of products that contain more energy per gallon than the ethanol that is used today in transportation fuels. By integrating the fermentation with extraction and chemical catalysis, you can reduce the energy demand of the overall process. This opens the door to selectively producing petrol, het and diesel blend stocks form lignocellulosic and cane sugars at near theoretically maximal yields.

Where can I read more?

A publication in Nature, which came out in November 2012: “Integration of chemical catalysis with extractive fermentation to produce fuels.” Pazhamalai Anbarasan, Zachary C. Baer, Sanil Sreekumar, Elad Gross, Joseph B. Binder, Harvey W. Blanch, Douglas S. Clark, and F. Dean Toste, Nature 491: 235-239, 2012.

 

 

 

 

 

 

 

 

 

 

 

 

 

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