SCIENCE & TECHNOLOGY
2014 GREEN CHEMISTRY AWARDS Presidential honors recognize chemical innovations that prevent pollution and PROMOTE SUSTAINABILITY STEPHEN K. RITTER, C&EN WASHINGTON
WITH POMP AND CIRCUMSTANCE, the Environmental Protection Agency presented
the 19th annual Presidential Green Chemistry Challenge Awards during a ceremony on Oct. 16 in Washington, D.C. These awards recognize chemical technologies that match or improve the performance of existing products and processes, are economically viable, and prevent pollution. Since the program’s inception, the winning technologies have accounted for reducing the use or generation of more than 826 million lb of hazardous chemicals, saving 21 billion gal of water, and eliminating 7.8 billion lb of carbon dioxide equivalent emissions to the air, according to EPA statistics. The following vignettes highlight this year’s winners.
ACADEMIC AWARD Shannon S. Stahl, University of Wisconsin, Madison, for developing aerobic
oxidation reactions for pharmaceutical synthesis using an inexpensive copper catalyst and O2 AS OXIDIZING REAGENTS GO, molecu-
lar oxygen is as green as they get. But two issues have stood in O2’s way, according to chemistry professor Shannon S. Stahl of the University of Wisconsin, Madison. “The combination of O2 with organic solvents is widely viewed as an insurmountable safety challenge,” Stahl says. “And there aren’t any aerobic oxidation reac-
tions good enough to bother dealing with the safety issue.” Stahl and his research group recently knocked down both barriers, an accomplishment that many in the pharmaceutical industry will welcome. O2 is rarely considered as an oxidant because of the risk of fire or explosion. That leaves chemists the option of using traditional oxidants such as permanganate and hypochlorite, which are often hazardous, generate excessive waste, or are costly. In many cases, alternative synthetic routes are chosen that avoid oxidation altogether, even if they are less efficient. Jessica M. Hoover, Janelle E. Steves, and their coworkers in Stahl’s group worked around those shortcomings by discovering
SMALL BUSINESS AWARD
GREEN OXIDATIONS Stahl’s team developed a catalyst system that enables safe O2 oxidations of various alcohols to aldehydes (shown).
R
OH
R
S
O
CH3CN
Amyris, Emeryville, Calif., for developing
O
O
O
O
H
NH2
H O
farnesane as a renewable drop-in replacement for petroleum-based diesel and jet fuel
H
O
H
Room temperature, H O2 from air
H
O
N
(CH3)3Si
S
H
O
OH Catalyst: 5 mol % Cu(bipyridine) 5 mol % TEMPO 10 mol % N-methylimidazole
OH H
O
O
H
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a catalytic system made up of a copper(I) bipyridine complex and the nitroxyl radical TEMPO. This catalyst works well to mediate selective oxidation of primary alcohols to aldehydes, oxidative coupling of alcohols with ammonia to make nitriles, and other reactions. The reactions proceed at room temperature in acetonitrile solvent with O2 from the air as the oxidant. The procedure avoids costly precious-metal catalysts and undesirable halogenated solvents. And water is the only waste product. To explore strategies for implementing the aerobic oxidations, Stahl has collaborated with Wisconsin chemical engineering professor Thatcher W. Root. Stahl has also established a unique noncompetitive research collaboration with Eli Lilly & Co., Merck & Co., and Pfizer. One of the most promising approaches emerging from these efforts involves a continuous-flow reactor for safely scaling up O2 oxidations that are complete in as little as three minutes. “This work is spectacular,” says Cornell University chemistry professor Geoffrey W. Coates, a 2012 award winner. “This is a real tour de force that combines mechanistic studies with organic synthesis and very elegantly applies it to an important area of chemistry.” Sustainability and economics are key when it comes to developing green reactions, Coates adds. Stahl’s approach includes everything process chemists look for––improving safety, saving time, reeling in cost, and preventing waste. “The interaction with leading pharmaceutical companies is a validation that this chemistry is on its way to the top.”
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FIRST-GENERATION BIOFUELS ethanol
and biodiesel (fatty acid methyl esters) provide a green alternative to petroleumderived fuels to help reduce greenhouse gas emissions. But the fuels have technical issues that limit their use—they can’t completely replace fossil fuels on their own. For example, ethanol has lower energy per volume than petroleum fuels and it’s not fully compatible with existing vehicles and fuel-distribution infrastructure. Amyris has taken a step toward the next generation of biofuels by engineering
mium-zinc sulfide shell and topped with organic ligands. Although they do contain cadmium, which is frowned upon by regulaQD Vision, Lexington, Mass., for developtory agencies, the company used life-cycle ing quantum dots for high-quality color and analysis to show that net cadmium in the energy-efficient displays and lighting environment actually drops when using its products. Lightbulbs and TVs require a QD VISION WAS recognized for findtiny amount of cadmium—only about 1 mg ing environmentally friendlier ways of per TV display. In addition, by reducing the manufacturing quantum dots used in amount of electricity consumed by a prodcommercial display and lighting product such as a TV, quantum dots reduce air ucts. Quantum dots are semiconducting emissions of cadmium by burning less fosnanoparticles, such as cadmium selenide sil fuel, in particular coal. The net amount or indium phosphide, that emit light after of cadmium entering the environment is being excited electronically. The color of therefore less, even after making the quanlight depends on the size of the particles, tum dots. with larger particles emitting red, medium“QD Vision takes the full life cycle of their products quite seriously,” says Eric J. Beckman, codirector of the Mascaro Center for Sustainable Innovation at the University of Pittsburgh and a 2002 award winner. “The work they’ve done on eliminating the use of some nasty organocadmium and organozinc precursors is top-notch. Despite the fact that they still use cadGREEN LIGHT QD Vision’s clean technology for mium—not a green maproducing quantum dots, contained in the oval tube terial—they have taken (right), is now being used in enhanced-color televisions. great pains to reduce the amount they use and to sized particles emitting green, and the track where it goes. And naturally, using less smallest particles emitting blue. The differenergy is a good thing.” ent size alters the band gap of the semiconductor and thus the color emitted. GREENER SYNTHETIC These materials are sought after for use in transistors, solar cells, light-emitting PATHWAYS AWARD diodes, and lasers because they have the highest color quality and are the most enSolazyme, South San Francisco, for develergy-efficient lighting technology known, oping engineered algae to produce customized explains Seth Coe-Sullivan, QD Vision’s oils via a fermentation process cofounder and chief technology officer. But the process for making quantum dots is not AS FAR BACK as the dawn of civilization, known for being green. people have used vegetable oils to prepare Quantum dots are typically prepared food, generate energy, and serve as chemivia a colloidal synthesis that involves toxic cal building blocks. Although vegetable metal alkyl precursors and unfriendly oils are relatively easy to modify chemiphosphorus-containing solvents such as cally, they are not directly customizable trioctylphosphine oxide. But the company for target applications. And modifying the reinvented the traditional synthesis by oils doesn’t come cheap: Achieving the selecting less toxic metal carboxylate predesired fatty acid chains from plant oils, or cursors and more benign long-chain alkane from petroleum- and animal-derived oils, solvents, improving yields and batch reis often energy-intensive, requires use of producibility and reducing solvent use and hazardous chemicals, and adds cost. energy consumption along the way. Solazyme scientists recognized that the QD Vision’s quantum dots have a solid pathways that plants use to make oils first cadmium selenide core coated with a cadevolved in algae. Synthetic biology and
GREENER REACTION CONDITIONS AWARD
QD VISION
baker’s yeast strains to convert sugar into the 15-carbon alkene β-farnesene instead of ethanol. The technology is built on synthetic biology concepts originating in Jay D. Keasling’s laboratory at the University of California, Berkeley. Amyris scientists sifted through metabolic pathways in bacteria that lead to hydrocarbons, homing in on the isoprenoid pathway that produces farnesene and other terpenes. The researchers then plugged farnesene-producing genes into yeast, which are more robust for industrial fermentations than bacteria, explains Joel Velasco, a senior vice president at Amyris. The company also developed an economical method to hydrogenate the multiple unsaturated bonds in farnesene to make farnesane, which can serve as a drop-in replacement for petroleum diesel or vegetable-oil-based biodiesel. Farnesane also can serve as an ingredient for making jet fuel. As a long-chain hydroFarnesane carbon, the molecule has a much higher energy density than ethanol, Velasco says, and its branched structure offers good cold-weather fuel performance. “This innovation by Amyris addresses renewability and reduction in greenhouse gases while also delivering improved performance in engine operation and eliminating other emissions such as sulfur dioxide,” comments David J. C. Constable, director of the American Chemical Society’s Green Chemistry Institute, which helps administer the awards process with EPA. “Sugar is unquestionably the new carbon source for many future chemicals and fuels, and its direct fermentation to farnesene is a great model for other companies to emulate.” Amyris operates a biorefinery in Brazil producing farnesene from sugarcane syrup, Velasco says. The company also has a business venture with French oil company Total to produce and market farnesane for diesel and jet fuel, which is being used in buses in Brazil and commercial aircraft globally. Besides biofuels, farnesene is being used as a biobased feedstock to make ingredients for lubricants, cosmetics, tire rubber, and more, Velasco says. With farnesene production on the upswing and production cost coming down, the company anticipates starting to turn a profit for the first time by the end of this year. “Farnesene is a nice building block hydrocarbon for us,” Velasco says. “When we first looked at farnesene, it was a dream on a PowerPoint. And now it’s a reality.”
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GREEN OILS Solazyme’s engineered algae technology platform enables any type of biomass-derived sugar to be converted into custom oils and other products.
Oil families Fuel
Oleic Lauric Midchain (C8–C10) Downstream processing
Long chain (C22)
Industrial Multiple high-value markets
Whole algal products Food Algal flour Algal protein Oil-drilling lubricant
Personal care
Oil-producing microalgae
industrial biotechnology now offer a green alternative to custom-make oils by reengineering algae with genes from oil-producing plants, notes Peter Licari, Solazyme’s chief technology officer. Algae convert CO2 and energy from the sun into biomass like plants. But because they float in water, they don’t need to build cellulose and lignin like freestanding plants. That makes them more efficient at producing useful proteins and oils. But Solazyme’s algae are not your ordinary pond scum, Licari notes. These are microalgae, a microscopic version of the algae commonly seen, he explains. The company’s original one came from the sap of a chestnut tree in Germany a century ago. These white algae live on sugar instead of CO2 and don’t need sunlight to grow. The company refined its technology such that its researchers can design the fastgrowing oil producers to selectively place desired fatty acid chains of any type at any position in the triglyceride backbone. Solazyme’s oils are currently being produced in facilities in Illinois, Iowa, and Brazil with a combined capacity of more than 120,000 metric tons per year. The oils are being sold for food, fuel, and industrial products. Some of Solazyme’s key partnerships include personal care products with Unilever, surfactants with AkzoNobel, and oleochemicals with Mitsui. “This is neat technology with great promise in the oils business,” says Eric. J. Beckman, codirector of the Mascaro Center for Sustainable Innovation at the University of Pittsburgh and a 2002 award winner. Most of the time with a green innovation, a crop-based product replaces a petroleum-based product, Beckman points
SOURCE: Solazyme
out. It’s an interesting twist that Solazyme is proposing a biological replacement for a biobased product, replacing farm-based oils with algal oils, he says. “Given that intensive farming is laden with impacts owing to fuel, fertilizer, water, pesticide, and land use, and that the recovery of products from crops is multistep and often energyand solvent-intensive, Solazyme could have something truly important here.”
tive. However, 40% more fluorosurfactant is required in the new formulations to meet firefighting foam performance standards. Rather than switching to a short-chain fluorosurfactant, Solberg came up with its Re-Healing formulations made from a blend of surfactants such as alkyl polyglycosides and alkyl sulfates, according to Steven Hansen, Solberg’s vice president and general manager. These compounds are derived from plant sugars and oils rather than from petroleum and are already used in household and personal care products such as soaps and toothpaste. The formulations also include a complex carbohydrate such as cane sugar molasses, a proprietary polysaccharide, glycol ether solvent, and glutaraldehyde as an antibacterial agent, Hansen says. This mix of components helps optimize performance in all kinds of weather. The foams are biodegradable, completely falling apart after six weeks. “For a long time, chemists have been halogenating organic compounds precisely SOLBERG
Fermentation tank
DESIGNING GREENER CHEMICALS AWARD Solberg Co., Green Bay, Wis., for develop-
ing halogen-free firefighting foams made from a blend of biobased surfactants and sugars FLUORINATED SURFACTANTS are criti-
GREENER FOAM Solberg’s halogen-free
cal components of firefighting foams. But the surfactants come with significant health and environmental concerns because they are persistent, bioaccumulative, and toxic. Solberg Co., a leading global maker of the foams, addressed the issue head-on with its halogen-free Re-Healing foaming liquid concentrates in which halogenated materials are replaced by an environmentally benign blend of biobased surfactants and complex carbohydrates. In 2006, with mounting evidence of the potential toxicity of long-chain fluorosurfactants, EPA and the fluorochemicals industry established a voluntary stewardship program to phase out the compounds. Foam formulators began switching from long-chain (C8 and longer) to short-chain (C6 and shorter) fluorosurfactants. The short-chain versions are still persistent, but they are not believed to be bioaccumula-
liquid concentrate is formulated to generate foam for preventing and fighting fires at airports and industrial facilities.
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because it helps different molecules survive in a variety of demanding end-use applications,” observes David J. C. Constable, director of the American Chemical Society’s Green Chemistry Institute, which helps administer the awards process with EPA. “However, we now know that persistence is generally not a good thing from an environmental perspective. Our experience with ozone depletion suggests that innovations like Solberg’s are essential. Their work once again proves that a desired chemical function in a commercial product can be delivered in a variety of ways and can be delivered with high performance, low cost, and greater environmental benefit.”
