Contributed by Lauren Winstel, ACS Green Chemistry Institute® Research Assistant
The Green Chemistry Challenge awards, administered by the EPA in partnership with the American Chemical Society (ACS) and its ACS Green Chemistry Institute® , recognize and promote innovations in chemical technology that reduce waste and the use and generation of hazardous chemicals. Past winners have gone on to commercialize their technology, grow their company, and improve upon their process with the increased recognition that the award provides, often leading to third party funding or buyout offers. The following is a summary and the future outlook of the most recent award winners, who were honored and recognized at the 21st Green Chemistry and Engineering Conference in Reston, Virginia last week.
1. Academic Category – Eric J. Schelter, Ph.D., University of Pennsylvania
The 2017 award in the Academic category features targeted coordination chemistry towards separations and recycling of rare earth metals, using tailored metal complexes and ligand synthesis. Rare earth metals are essential components in many modern technologies, from personal electronics and lighting to renewable energy. However, these applications require various mixtures of elements which are difficult to separate once combined. In order for rare earth metals to be reused, the pure elements need to be isolated and extracted from consumer products in various recycling streams, which is one of the biggest challenges related to critical elements. Electronic waste is currently an elemental sink, to the point that the amount of rare earth metals found in e-waste is greater than known quantity within global reserves of such metals.
In order to solve this problem, Professor Schelter and his research group have come up with a simple and cheap method of extraction using a ligand framework that takes advantage of solubility differences. Through combining metal mixtures with a benzene or toluene solvent, solid-liquid equilibrium can be identified which allows for quick separation. Using the example of Neodymium (Nd) and Dysprosium (Dy), which are often used in large magnets, Schelter’s experiments showed that when starting with a 50/50 mixture of the two elements, a single pass from the ligand framework created 98% pure separation, which is the minimum purity necessary for reuse.
When analyzing the greenness of this process, the use of benzene raises a few concerns. Schelter and his group are well aware and plan to address this unsustainable solvent in future iterations of the technology. In the future, Schelter and his group plan to make modifications to the ligand framework, working towards using kinetic control to achieve purification, as well as focus on recycling chemistry and eventually attaching the ligand to a resin.
2. Small Business Category – UniEnergy Technologies, LLC
The 2017 award in the Small Business Category features an advanced vanadium redox flow battery for grid energy storage applications produced by UniEnergy Technologies. The need for energy storage goes hand in hand with renewable energy technology – many arguments against solar and wind power focus on their inconsistency and lack of reliability over 24 hour days. Unfortunately, times of maximum generation for such renewable technologies often do not correspond with maximum usage in the early mornings and late afternoons. Without storage options, the produced power goes to waste. However, if the abundance of energy produced during daylight hours or times of continuous wind patterns could be stored and used when needed, renewables would become more reliable and readily available than nearly any other energy source.
This new battery, called the UniSystemTM, achieves what many energy storage attempts have failed to do before. The vanadium electrolyte technology represents a breakthrough chemistry technique due to the increased energy density and broader operating temperature, allowing for megawatt scale storage that can be deployed in nearly any location on Earth, while also using much fewer chemicals with increased stability. Active heat management and self-contained cooling allow the battery to regulate itself, while also holding the power and energy in separate tanks, allowing for flexible and tunable usage that is not possible with conventional batteries. This battery also has a longer lifetime than those currently on the market, and all materials are fully recyclable and non-toxic at end of life since the vanadium electrolyte is water based, immutable and does not degrade.
3. Greener Synthetic Pathways Category – Merck & Co.
The 2017 award in the Greener Synthetic Pathways category features an improved formula for Letermovir, an antiviral therapeutic agent for treatment of human cytomegalovirus. This pharmaceutical route is greener than the original method in many ways. The original route featured only 10% yield, estimated CO2 emissions of 1,657 kg, as well as 9 different solvents throughout the process and late stage chiral resolution which can have unpredictable results. The new process features a more reliable late stage asymmetric aza-Michael transformation using a fully recyclable and chemically stable organocatalyst. The greener route also achieves high conversion and purity, increasing overall yield by over 60% at a low cost, all while using a through process with only 2 solvents and recycled reagents.
The final catalyst in this process is toluene, which is not ideal. However, a lot of effort was put towards optimizing this drug for sustainability and atom economy with positive results; the new process reduced the carbon footprint of Letermovir by 89% and water usage by 90%. With future improvements, Merck believes that this process is only a few steps away from zero-waste manufacturing.
4. Greener Reaction Conditions Category – Amgen Inc. and Bachem
The 2017 award in the Greener Reaction Conditions category features an improved technology for solid phase peptide synthesis, created as part of a collaboration between Amgen and Bachem. The pharmaceutical industry is often very energy intensive with high consumption of water, as well as inefficiently using many different materials and solvents in high quantities while yielding very small amounts of product. Peptide-based pharmaceuticals are an important part of therapeutics, including ParasabivTM and its active ingredient Etelcalcetide which is used to treat hyperparathyroidism. The newly designed manufacturing process has improved upon many of the unsustainable factors: shortened development processes equating to a 56% decrease in manufacturing time; high coupling yields resulting in a 5-fold increase in manufacturing capacity; the elimination of 1,440 cubic meters of waste, including 750 cubic meters of aqueous waste; and a 51% decrease in solvent use creating much cleaner reactions.
The future of this process lies in continued solvent reevaluation – according to green chemistry principles as well as Amgen executives, “the best solvent is no solvent at all.” Due to its broad applicability, this synthesis process has the potential to be used for manufacturing of many other peptide-based pharmaceutical products in the future.
5. Designing Greener Chemicals Category – Dow Chemical Co. and Papierfabrik August Koehler SE
The 2017 award in the Designing Greener Chemicals category features a breakthrough sustainable imaging technology for thermal paper that uses air-voided structures. Thermal paper is very prevalent in everyday life, widely used for point of sale receipts, tickets, tags, and labels, all of which are often quickly discarded after use. The new manufacturing method takes a process that was previously chemically intensive and environmentally toxic due to lack of recyclability, and turns that process into a physical change reaction that occurs completely void of chemical interaction.
The new paper consists of three simple layers. The top layer is comprised of voided opaque polymers, with a colored layer underneath, followed by a base layer. When heat is applied to the opaque layer, the air void particles instantly collapse to reveal the color below. This process eliminates the need for ink, avoids manufacturer and consumer exposure to imaging chemicals, as well as improves long term storage capabilities since the contrast created will not fade even under direct and severe sun exposure. The final product is compatible with existing thermal printers and is also directly recyclable with normal paper recycling steams, which creates a new recycled feedstock potential that was previously sent into landfills.
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