Chemistry Magazine: Quick Read

 

Quick Read

Want to put your chemical skills to work solving one of humanity’s most pressing problems? Research aiming to create fuel from cellulose could be calling you.


What’s the most critical problem that humanity will face over the next 50 years? That’s the question that Nobel laureate Richard Smalley asked audiences as he toured the country in the final months of his life. “In every case,” Smalley wrote, “after a bit of discussion, the audiences have agreed that energy is the single most important issue we face.”

Smalley assembled a list of the top 10 problems and used this list to challenge both scientists and the public. “When we look at a prioritized list of the top 10 problems, with energy at the top, we can see how energy is the key to solving all of the rest of the problems—from water to population.”

Smalley, a chemist, believed that the chemistry community can, and must, play a leading role in solving the energy problem. Chemists, material scientists, and chemical engineers will be involved in energy-related innovations across a broad spectrum of technologies—from photovoltaics to nanotech-based energy storage and transmission systems, from lightweight materials for energy-efficient vehicles to clean-coal technology.

Some of these advances, unfortunately, are still years off in the future. Right now, however, among the many areas of energy research, one has really captured the attention of scientists, investors, celebrities, policy wonks, and politicians. This year’s hot topic in energy is biofuels.

Uniting George Bush . . . and Willie Nelson?
In his 2006 State of the Union speech, President Bush said, “We must change how we power our automobiles. . . . We’ll fund additional research in cutting-edge methods of producing ethanol, not just from corn, but from wood chips and stalks, or switchgrass. Our goal is to make this new kind of ethanol practical and competitive within six years.”

Another Texan, Willie Nelson, is also a big advocate for biofuels, especially biodiesel. Earlier this year, Nelson received the Award for Outstanding Achievement from the U.S. Environmental Protection Agency’s (EPA) Region 9 for bringing biodiesel stations to California. With his own “BioWillie” brand of fuel now available at pumps nationwide, Nelson has dramatically increased public awareness of biodiesel, especially within the trucking industry.

Biofuels promise big benefits, such as reducing greenhouse gas emissions, improving air quality, creating domestic jobs, and decreasing reliance on foreign oil. With oil and gas prices ratcheting ever higher, biofuels have become economically attractive, and investors are scrambling to build new ethanol plants.

The United States produced 4.3 billion gallons of ethanol for fuel in 2005, more than double the amount produced just five years earlier. Although this represents only about 2% of the total amount of gasoline consumed in the United States today, the U.S. Department of Energy has set an aggressive goal of displacing 30% of gasoline demand with biofuels, primarily ethanol, by 2030.

Producing Biofuels: Issues and Alternatives
Currently, almost all ethanol production starts with starch from corn kernels. Enzyme hydrolysis breaks down the long carbohydrate chains of starch into shorter chains and eventually to individual glucose molecules. Yeast fermentation then converts the glucose to ethanol and carbon dioxide. Distillation and water-removal steps complete the production process. The process is not a new one—humans have been making alcohol from grain for millennia.

Many celebrities back environmental causes, but few have their own brand of biofuels

Many celebrities back environmental causes, but few have their own brand of biofuels.
(Click on image to enlarge)
WWW.BIOWILLIE.COM

Microbes ferment sugars to ethanol, which is then separated from the mixture of ethanol, water, microbes, and residue and purified through distillation.

Microbes ferment sugars to ethanol, which is then separated from the mixture of ethanol, water, microbes, and residue and purified through distillation.
(Click on image to enlarge)
U.S. DEPARTMENT OF ENERGY

Switchgrass is one of the most promising sources of cellulosic biomass that could be converted into ethanol.

Switchgrass is one of the most promising sources of cellulosic biomass that could be converted into ethanol.
OAK RIDGE NATIONAL LABORATORY


Biodiesel is created by chemically reacting vegetable oils or animal fats with alcohol (usually methanol) in the presence of a catalyst (often sodium or potassium hydroxide). Transesterification results in the production of the methyl esters that constitute biodiesel. Most biodiesel in the United States comes from soybean oil or restaurant greases. In 2005, about 75 million gallons of biodiesel were produced, tripling the 25 million gallons produced in 2004.

Although these biofuels clearly come from renewable sources, the energy and environmental implications of their use have been less clear. In recent years, energy policy experts have vigorously debated the efficiency of the corn-kernels-to-ethanol process. When the significant energy costs of growing, harvesting, and transporting corn are included in the production equation, does the grain-to-ethanol production process really result in a net gain of energy?

Two review articles, both published in 2006, may have finally settled this contentious debate, coming down firmly on the pro-ethanol side. Farrell and colleagues, in a paper published in Science (DOI: 10.1126/science.1121416) and Hammerschlag in Environmental Science & Technology (DOI: 10.1021/es052024h) reviewed the literature and concluded that the production of starch ethanol from corn is less petroleum-intensive than the production of gasoline. (Biodiesel has an even more positive energy balance.) Both articles, however, point to the production of ethanol from biomass, such as cellulose and hemicellulose, as a much more energy-efficient alternative for the future.

Ethanol from Cellulose
As outlined by President Bush in his State of the Union speech, the long-term goal in the biofuels industry is to use biomass as a starting material. Biomass includes cellulosic plant matter such as stalks, leaves, and cobs from corn (called “corn stover”); stalks from wheat (called “wheat straw”); or entire plants like poplar or switchgrass, which are highly efficient at converting sunlight to plant matter.

Unfortunately—as anyone who has tried to survive on a diet of grass, bark, and corn stalks can testify—cellulose is very difficult to break down and digest. The Energy Department’s website on biofuels (http://genomicsgtl.energy.gov/biofuels/index.shtml) describes the cellulose problem this way:

“The core barrier is cellulosic-biomass recalcitrance to processing to ethanol. Biomass is composed of nature’s most ready energy source, sugars, but they are locked in a complex polymer composite exquisitely created to resist biological and chemical degradation. In nature, ruminant animals, including cows, sheep, and goats, have evolved special digestive systems that allow them (and the microbes that live in their complex stomachs) to break down cellulose into smaller, energy-rich, sugar molecules. Now, the biofuels industry is evolving its own set of technologies for breaking down cellulose into small, energy-rich molecules such as ethanol.”

Pursuing the biomass-to-ethanol prize are many researchers in academe, government, and industry. Federal U.S. agencies with strong programs include the Energy Department’s National Renewable Energy Laboratory (www.nrel.gov/biomass), the Department of Agriculture, the EPA, and the Department of Defense’s Defense Advanced Research Projects Agency. Industrial players include large, established companies (e.g., Archer Daniels Midland, Cargill, Dupont, Monsanto, and Syngenta) as well as newer, biotech companies (e.g., Agrivida, Celunol, Ceres, Edenspace, Genencor, Genomatica, and Novozymes). The United States is not alone in this research effort, and two international companies (Iogen in Canada and Abengoa in Spain) are among the first in the world to build cellulose-to-ethanol production facilities.

Researchers are pursuing innovations at every step along the biofuels production chain—bio-engineered crops with more accessible sugars, improved pretreatment methods, and more efficient hydrolysis and fermentation methods. The innovations will come from a variety of disciplines, including chemistry, microbiology, agronomy, genomics, and systems biology.

Opportunities for Chemists and Chemical Engineers
Within the biofuels and bio-based materials industry, there are increasingly many opportunities for chemists and chemical engineers. One young chemical engineer who plans to play a major role in the future is Michael Raab (ACS ’91), 33, founder and chief scientist of Agrivida. Raab was recently profiled by Technology Review as a member of the TR35, the magazine’s annual selection of 35 innovators under the age of 35 who are “inventing the future of technology.”

Agrivida’s approach focuses on engineering the plants themselves to make them more attractive as feedstocks. Raab says, “We have a proprietary technology that allows us to control protein activity in the plant. This allows us to make plants that are producing enzymes for cell wall degradation without harming the plant’s physiology, growth, or reproduction. After the plants are harvested, the enzymes can be activated and are free to degrade the plants’ cell walls into sugars for fermentation.”

Raab, who has a Ph.D. in chemical engineering from the Massachusetts Institute of Technology, is upbeat about the biofuels industry and encourages others to join him. When asked why chemists and engineers should care about biofuels, he replies, “One reason why chemists and engineers should care is that many of their traditional research areas are quite mature. Chemical engineering grew with the petroleum industry, and this is a chance for the field to find a new focus that incorporates all of their skills. It’s an area where they can create a lot of value. The situation is true for chemists as well, where the chemistry of converting agricultural raw materials into higher-valued products is still not well understood and could certainly use more advancement.”

And if those aren’t good enough reasons, Raab adds one more. “Also, by working on biofuels, these professionals can contribute to one of the largest problems of our generation: providing sustainable energy.”

I have no doubt that Richard Smalley would approve.

Randy Wedin (ACS ’77) writes from Wayzata, MN. After spending a decade working for the ACS and as a Congressional Science Fellow, he launched a freelance writing business, Wedin Communications, in 1992.

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