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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.
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Many
celebrities back environmental causes, but few have their own brand of
biofuels.
(Click on image to enlarge)
WWW.BIOWILLIE.COM
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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
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Switchgrass
is one of the most promising sources of cellulosic biomass that could
be converted into ethanol.
OAK RIDGE NATIONAL LABORATORY
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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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