A Green Movement in The Cosmetic Industry: A Shift From Petrochemical-Based To Bio-Based Products

By Margaret Zhang, a graduate student in the Winnik Group at the University of Toronto and the Secretary for the GCI

The Cosmetic Industry

Cosmetics are products that can be applied to the human body to beautify, cleanse, and target certain topical concerns.1 The global revenue of the industry was 380 billion USD in 2019 and is expected to reach 463 billion USD in 2027.2 You can find a variety of cosmetic products in drugstores ranging from lipsticks and eyeshadows to moisturizers and anti-aging creams.

Figure 1. Cosmetic products.3

Current Problems in The Cosmetic Industry

A long-term problem in the industry is the usage of petrochemical-derived materials in cosmetic formulations.4 These chemicals are obtained from crude oil and natural gas.5 They can be toxic, irritating, and allergen-inducing.4 For example, carcinogenic benzophenone can be found in sunscreen formulations.6 Sodium lauryl sulfate (SLS) is often used in cleansers despite it can cause skin irritations.4 Synthetic colors were evidenced to induce allergies.4

Moreover, petrochemicals are non-renewable, non-sustainable, and exert negative impacts on the environment.4 Most cosmetic products contain organic solvents which release volatile organic compounds (VOCs). VOCs are precursors to ozone and secondary aerosols that can lead to global pollution.7 Considering these negative health and environmental effects, it is essential to develop a more sustainable alternative to circumvent such deleterious effects.  

Bio-based Alternatives for Petrochemicals in The Cosmetic Industry

An emerging trend in the cosmetic industry is to replace petroleum-based ingredients with more abundant bio-based ingredients (e.g., plant-sourced), producing so-called “biocosmetics”.4

Green Biotechnology in The Cosmetic Industry

There are many biotechnological advancements in synthesizing biocosmetics. One classical method is fermentation processes. Such processes involve the usage of microorganisms (e.g., bacteria, enzymes) to produce the desired products (e.g., organic acids, antibiotics).8 In industry, these processes are usually carried out in bioreactors, which are containers that can provide the optimal temperature and pH for these reactions (Figure 2).9 One example of using fermentation is the production of butylene glycol, which is used in cosmetic products to provide moisturizing effects.8 Traditionally, butylene glycol is synthesized via dehydrogenation of carcinogenic acetaldehyde.10 Instead, fermentation can be employed as a safer and simpler method.6 In addition to butylene glycol, fermentation can be used to produce many other useful ingredients in cosmetics such as hyaluronic acid (anti-aging) and Kojic acid (depigmenting).11,12

Figure 2. Industry scale bioreactors used to carry out fermentation processes.13

A more recent approach for specific bio-based reagents is using genetic editing via recombinant DNA technology (Figure 3). This method involves the insertion of exogenous genes of interest (i.e., DNA) into a bacterial plasmid to produce recombinant DNA vectors, which can be used to transduce cells, forcing them to generate desirable products.14 In the field of cosmetics, this technology can be used to produce enzymes such as superoxide dismutase (SOD) and proteases. SOD is often formulated into sunscreen to regulate the number of reactive oxygen species and reactive nitrogen species formed upon UV exposure.15 Proteases are usually formulated in exfoliators because they can break down peptides into amino acids.8 Recombinant DNA technology can also be used to produce proteins by using microalgae.8 Some notable examples include Spirulina and Chlorella; both of which were evidenced to have anti-aging effects.16,17

Figure 3. Recombinant DNA technology.18

Challenges in The Green Movement

Although biocosmetics hold many advantages as discussed in previous paragraphs, there are many challenges in the green movement. Biocosmetics are heavily dependent on production of plants which also vary with seasonal changes.4 Maintaining constant plant supply throughout the year is therefore challenging. Green movement would also limit the vibrance of many make-up products.4 Furthermore, there is a lack of global standards regarding the ingredients of biocosmetics. Continued efforts in this field can lead to substantial progress in transforming the cosmetic industries towards more renewable, safe, and potentially more cost-effective solutions.

References

  1.  FDA. Cosmetics Overview https://www.fda.gov/industry/regulated-products/cosmetics-overview (accessed Apr 28, 2022).
  2. Chouhan, Nitesh; Vig, Himanshu; Deshmukh, R. Cosmetics Market by Category (Skin and Sun Care Products, Hair Care Products, Deodorants & Fragrances, and Makeup & Color Cosmetics), Gender (Men, Women, and Unisex), and Distribution Channel (Hypermarkets/Supermarkets, Specialty Stores, Pharmacies, Onlin; 2021.
  3.  ECHA. Chemicals in cosmetics https://chemicalsinourlife.echa.europa.eu/chemicals-in-cosmetics (accessed Apr 28, 2022).
  4. Goyal, N.; Jerold, F. Biocosmetics: Technological Advances and Future Outlook. Environ. Sci. Pollut. Res. 2021, No. 0123456789. https://doi.org/10.1007/s11356-021-17567-3.
  5. Petrochemicals 1.; 2020. https://doi.org/10.1016/B978-0-12-809923-0.00012-6.
  6. IARC monographs on the evaluation of carcinogenic risks to humans. IARC Monogr Eval Carcinog Risks to Humans 2010, 93:9–38. https://doi.org/10.1136/jcp.48.7.691-a
  7. S. C. Pugliese; J. G. Murphy; J. A. Geddes; and J. M. Wang. The impacts of precursor reduction and meteorology on ground-level ozone in the Greater Toronto Area. Atmos. Chem. Phys., 2014, 14, 8197-8207.
  8. Gomes, C.; Silva, A. C.; Marques, A. C.; Lobo, J. S.; Amaral, M. H. Biotechnology Applied to Cosmetics and Aesthetic Medicines. Cosmetics. 2020, 7 (2), 1–14. https://doi.org/10.3390/COSMETICS7020033.
  9. Waites, M.J.; Morgan, N.L.; Rockey, J.S.; Higton, G. Industrial microbiology: An introduction, 1st ed.; Blackwell Science: Oxford, UK, 2001; pp. 1–79.
  10. Fulmer, E. I.; Christensen, L. M.; Kendall, A. R. Production of 2,3-Butylene Glycol by Fermentation: Effect of Sucrose Concentration. Ind. Eng. Chem. 1933, 25 (7), 798–800. https://doi.org/10.1021/ie50283a019.
  11. Mohamad, R.; Mohamad, M.S.; Suhaili, N.; Salleh, M.M.; Ariff, A.B. Kojic acid: Applications and development of fermentation process for production. Biotechnol. Mol. Biol. Rev. 20105, 24–37.
  12. Nobile, V.; Buonocore, D.; Michelotti, A.; Marzatico, F. Anti-aging and filling efficacy of six types hyaluronic acid-based dermo-cosmetic treatment: Double blind, randomized clinical trial of efficacy and safety. J. Cos. Derm. 201413, 277–287.
  13. Bioreactors https://www.engr.colostate.edu/CBE101/topics/bioreactors.html (accessed Apr 28, 2022).
  14. Tortora, G.J.; Funke, B.R.; Case, A.L. Microbiologia, 12th ed.; Artmed: Porto Alegre, Brazil, 2017; p. 802.
  15. Wang, Y.; Branicky, R.; Noë, A.; Hekimi, S. Superoxide Dismutases: Dual Roles in Controlling ROS Damage and Regulating ROS Signaling. J. Cell Biol. 2018, 217 (6), 1915–1928. https://doi.org/10.1083/jcb.201708007.
  16. Campos, M.; Camargo, F.B., Jr.; Corauce, D. Spirulina Containing Cosmetic Composition and Cosmetic Treatment Method. European Patent EP12768486. Available online: https://patents.google.com/patent/US20140023676A1/en (accessed on 30 April 2022).
  17. Yang, B.; Liu, J.; Jiang, Y.; Chen, F. Chlorella species as hosts for genetic engineering and expression of heterologous proteins: Progress, challenge and perspective. Biotechnol. J. 201611, 1244–1261.
  18. Suza, Walter; Lee Donald; Hanneman, Marjorie; Hain, P. 11. Recombinant DNA Technology

https://iastate.pressbooks.pub/genagbiotech/chapter/recombinant-dna-technology/ (accessed Apr 29, 2022).

Vegetable Oils as Green Solvents

By Jose Jimenez Santiago, a graduate student in the Song Group at the University of Toronto

The problem with solvents

Solvent has been defined as a “liquid that has the property to dissolve, dilute, or extract other materials without causing a chemical modification of these substances or itself”1. In chemical sciences and industry, most solvents come from the petrochemical industry. In 2020, the production of organic solvents surpassed 28 million metric tons2. This intensive consumption of solvents comes with a large concern with respect to sustainability, environment, safety, and health.  For instance, in the pharmaceutical industry, solvents can double the total mass of reagents and additives needed to produce a target compound. In this regard, the solvent of choice accounts for the environmental impact of a pharmaceutical product2-4.

How to select a good solvent

The 5th green chemistry principle promotes the use of Safer Solvents and Auxiliaries3.  Ideally, alternatives to petroleum-based solvents should fulfill the following requirements: 1) does not emit volatile organic compounds (VOCs); 2) be low toxicity for humans; 3) have a limited impact on the environment (i.e, be eco-friendly); 4) be obtained from renewable sources; 5) have high dissolving power, and 6) be easy to recover4.

There has been a huge effort to mitigate the negative impact of solvents. In this context, “sustainable” or “green” solvents describe those that are eco-friendly, non-toxic, or biodegradable5. Green solvents can be classified into seven categories: 1. bio-based solvents (from renewable sources), 2. eco-friendly (good health and safety risk profile), 3. water (renewable and non-toxic), 4. liquid polymers (non-volatile, non-toxic), 5. fluorinated solvents (non-flammable and non-toxic), 6. ionic liquids (non-volatile, thermally stable), 7. supercritical fluids like CO2 (inert, recyclable)5,6.

Vegetable oils as green solvents

Regarding the different green solvent classes, vegetable oils belong to the bio-based solvent class (category 1). These oils have the advantage of offering a positive impact on the environment and human health because they are biodegradable, non-toxic, and non-volatile. Vegetable oils, commonly produced from plant seeds or fruits (e.g., rapeseed, sunflower, olive, etc.), are non-polar and lipophilic systems whose composition is variable and complex depending on the origin and production method. The main components in vegetable oils are triglycerides, which are composed of three fatty acid molecules esterified into one glycerol molecule and constitute between 95-98% of the oil (Figure 1). The physical and chemical properties of each oil are determined by the proportion and position of fatty acids on the glycerol backbone and the ratio of these triglycerides in the oil7,8. In the next section, some recent innovative applications of this new class of solvents are discussed.

Figure 1. Major components in different vegetable oils1.

Applications of Vegetable Oils as Green Solvents

  1. Innovative Techniques for Extraction of Bioactive Compounds

Bioactive compounds from plants, algae, yeast, and fungi are usually extracted with petrochemical-based solvents in the pharmaceutical industry. However, the energy employed for distillation and the large amount of solvent used require innovative techniques. In this context, the solvent property of vegetable oils in combination with ultrasound has helped to achieve a greener extraction procedure. For example, the ultrasound-assisted extraction (UAE) of carotenoids from fresh carrots was recently achieved using sunflower oil as the solvent (Figure 2). Surprisingly, the extraction times have been reduced by more than half compared to conventional solvent extraction9.

Figure 2. Ultrasound-assisted extraction (UAE) of carotenoids with sunflower oil9.

2. Reaction Media for Multicomponent Synthesis

In 2021, a research article in the Green Chemistry Journal10 demonstrated the effectiveness of palm oil in a multicomponent reaction. The Biginelli reaction (Figure 3) is one of the most popular multicomponent reactions involving the condensation of urea, an aldehyde, and a β-keto ester to give dihydropyrimidinones (DHPMs). Typically, this reaction is performed in conventional non-renewable, petroleum-based solvents such as cyclohexane, THF, dioxane, toluene, and hexanes. In this study, the yield of the reaction did not decrease when using palm oil over cyclohexane. Moreover, using waste palm oil was possible without a considerable decrease in yield. Finally, the study showed that it is possible to recover the solvent (palm oil) and reuse it for at least 5 additional reactions without losing its effectiveness (Figure 4).

Figure 3. Model reaction for solvent screening10.
Figure 4. Reusability study for palm oil as a green solvent10.

3. Reaction Media for Catalytic Coupling Reactions

Another recent application of vegetable oils in organic synthesis has been as a solvent in metal-catalyzed cross-coupling reactions11. Carbon-carbon bond formations are among the most frequently used transformations in modern chemistry, patent literature, and the fine chemical industry. In 2021, a study demonstrated that food-grade and waste lipids are excellent solvents for homogeneous catalysis11. A variety of oils were tested (Figure 5) and the model reaction was the Suzuki-Miyaura coupling catalyzed by palladium (Pd) (Chart 1).

Figure 5. Vegetable, semisynthetic, and animal-based oil evaluated in this study11.

The results are shown in Chart 1 with the optimized conditions for a variety of oils tested. Semisynthetic oils (green) were as effective as traditional solvent used in homogeneous catalysis (red). Most of the vegetable oils (orange) were efficient for the transformation. Triglycerides originating from animals like butter and fish oil (blue) worked well as the reaction media as well as some natural waxes (pink). In this study, the exceptional performance of vegetable oil and related lipids as solvents was further confirmed for several other important Pd-catalyzed transformations including the Hiyama, Stille, Sonogashira and Heck cross-coupling reactions.

Chart 1. Model cross-coupling reaction and catalytic results of different oils and solvents screened11.

In a very recent study12, a protocol for the more challenging carbon-nitrogen bond coupling reaction was developed. The model reaction, the Buchwald-Hartwig amination, is shown in Chart 2. This reaction is sensitive to the solvent used and even petroleum-based solvents gave low yields in this reaction (red). Nevertheless, semisynthetic oils give excellent yields for the reaction (green) but vegetable oils dramatically reduce the catalytic performance (orange). Animal oils and natural waxes (pink and blue) gave a high yield in catalysis. Current research is focused on expanding the substrate scope for this reaction with the best solvents and using them for other important catalytic reactions like carbon-oxygen bond formation.

Chart 2. Model cross-coupling reaction and catalytic results of different oils and solvents screened12.

In conclusion, vegetable oils have emerged as a potential sustainable replacement for petroleum-based solvents. Great progress has been done in using them for the extraction of bioactive compounds and purification. Vegetable oils have the potential to be an ecological and economic solution and alternative to petroleum-based solvents and other hazardous solvents. Future scientific innovations will make them attractive at the large scale in the pharmaceutical and fine chemical industries.

References

  1. Yara-Varón, E.; Li, Y.; Balcells, M.; Canela-Garayoa, R.; Fabiano-Tixier, A.; Chemat, F. Molecues 2017, 22, 1474-1498.
  2. Constable, D. J. C.; Jimenez-Gonzalez, C.; Henderson, R. K. Org. Process Res. Dev. 2007, 11, 133-137.
  3. https://www.acs.org/content/acs/en/greenchemistry/principles/12-principles-of-green-chemistry.html
  4. Chemat, F.; Vian, M. Alternative Solvents for Natural Product Extraction; Springer: Heidelberg, Germany, 2014; pp. v-vi, ISBN 978-3-662-43627-1.
  5. Reichardt, C. Org. Process Res. Dev. 2007, 11, 105-113.
  6. Alfonsi, K.; Colberg, J.; Dunn, P. J.; Fevig, T.; Jennings, S.; Johnson, T. A.; Kleine, H. P.; Knight, C.; Nagy, M. A.; Perry, D. A. Green Chem. 2008, 10, 31-36.
  7. Kerton, F.; Marriot, R. Alternative Solvents for Green Chemistry, 2nd ed.; RSC Publishing: Cambridge, UK, 2013; pp. 149-171, ISBN 978-1-84973-595-7.
  8. Chen, B.; McClements, D. J.; Decker, E. A. Crit. Rev. Food Sci. Nutr. 2011, 51, 901-916.
  9. Li, Y.; Fabiano-Tixier, A. S.; Tomao, V.; Cravotto, G.; Chemat, F. Ultrason. Sonochem. 2013, 20, 12-18.
  10. Noppawan, P.; Sangon, S.; Supanchaiyamat, N.; Hunt, A. J. Green Chem. 2021, 23, 5766-5774.
  11. Gevorgyan, A.; Hopmann, K.; Bayer, A. Green Chem. 2021, 23, 7219-7227.
  12. Gevorgyan, A.; Hopmann, K.; Bayer, A. Organometallics https://doi.org/10.1021/acs.organomet.1c00517

Cranking up the Gears on Ammonia Production

By Eloi Grignon, PhD student in the Seferos Group at the University of Toronto

Modern agriculture does not begin in a field but in a reactor. Here, nitrogen and hydrogen enter and are transformed to ammonia by iron catalysts on the reactor bed. This ammonia, which is produced at the colossal scale of 230 million tonnes per year, is the fertilizer that sustains the nearly 8 billion people on our planet. Without it, our population would drop by half.1

This awesome industrial synthesis is the Haber-Bosch process. Arguably the most impactful of all chemical reactions on the modern world, its importance has been recognized by three Nobel prizes (Haber in 1918; Bosch in 1931; Ertl in 2007) and its ubiquity is such that half of the nitrogen atoms in our bodies have touched the iron catalysts of a Haber-Bosch reactor.

Figure 1. World population with and without synthetic ammonia. From [1].

However, the Haber-Bosch process is not innocuous. Although the reaction is exothermic, the high activation energy required to break the nitrogen triple bond forms a kinetic barrier. As such, appreciable formation of ammonia is only obtained by running the synthesis at 400-500 oC, where the catalyst is most active, and 100-150 bar, to compensate for the equilibrium shift caused by the heat. Coupled with the massive scale of the reaction, these harsh conditions make Haber-Bosch one of the most energy-consuming industrial processes in the world; ammonia production uses up 2% of global energy and accounts for 3% of total CO2 emissions.2

It is no surprise that intensive research efforts have been geared towards achieving ammonia production under ambient conditions. The primary benefit is of course a reduction in energy consumption associated with heat. However, the industrial profile of ammonia production would also change with a room temperature synthesis. Currently, Haber-Bosch plants need to be large in order to offset their high production costs and turn a profit. With a low-cost, low-energy approach, production could become far more modular, with small-scale reactors being placed at the point of use. This decentralization would not only reduce transportation costs but also allow for fertilizer production in regions where large-scale Haber-Bosch infrastructure is lacking.

To achieve ambient ammonia production, a variety of reaction methodologies have been envisioned. Although approaches such as molecular catalysis and electrochemistry are interesting in their own right, the focus of the present post is on recent milestones attained through mechanochemistry. As the name implies, mechanochemistry harnesses mechanical force to drive chemical reactions forward. At the research scale, this is typically done in milling jars where balls are used to grind solid reagents together. Not only do these syntheses bypass the use (and waste) of solvents, but they can also often afford increased reaction yields and even access to previously unattainable products.

A significant breakthrough was achieved in 2021 when Han et al. reported a two-step mechanochemical synthesis of ammonia using commercially available iron powder as the catalyst.3 In this protocol, nitrogen dissociation first occurs on mechanically induced defects on the catalyst surface to yield iron nitrides. The ball mill is then emptied of nitrogen and refilled with hydrogen, and subsequent reduction of the iron nitride intermediates affords ammonia. The overall procedure requires about 2 days of milling, does not surpass 45 oC, and results in an ammonia concentration of 82.5 vol%, which is considerably higher than the 25 vol% of the conventional Haber-Bosch process.

Figure 2. Two-step ammonia synthesis. Nitrogen first dissociates on defects on the catalyst surface to form nitrides. Then, the nitrides are hydrogenated to form ammonia. Both steps occur while milling. From [3].

Still, Han et al.’s approach requires two discrete steps, which is not conducive to industrial application. Ideally, ammonia should be produced continuously without needing to change the gas supply. This important requirement was addressed in a recent work by Schüth and coworkers, who modified a ball mill to enable continuous ammonia synthesis in the presence of a cesium-promoted iron catalyst.4 Their most performant system was able to sustain the reaction for several days at room temperature. While certain details, such as catalyst activity at extended milling time and the need for moderate pressures (20 bar), can still be improved, this represents an impressive step forward for the realization of industrially relevant room-temperature ammonia production.

Figure 3. Setup for the continuous mechanocatalytic ammonia synthesis. Inlets of individual gases (1). Dosing of gases using mass-flow-controllers, manometer (2). Modified Retsch MM400 shaker mill with home-built jar equipped with thermocouple and gas connections (3). Back-pressure regulator (4). From [4].
Figure 4. Continuous ammonia production over 60 hours. Spikes are due to rest periods for the ball mill. From [4].

An interesting aspect of Schüth’s process pertains to the addition of promoters to the iron catalyst. Alkali promoters can improve the chemisorption ability of the catalyst, which greatly increases the amount of nitrogen that can be dissociated in the first step of the synthesis (N2 needs to first be adsorbed onto the catalyst before activation can occur). These promoters are common in traditional Haber-Bosch but are typically introduced as alkali oxides due to the volatility of the metals. However, the presence of oxygen tends to block nitrogen adsorption sites, which mitigates the benefits of the alkali promoter.5 In the mechanochemical approach, the use of mild conditions means that volatility is not an issue. As a result, cesium metal can be directly added to the iron catalyst (at around 2%), which greatly enhances catalytic activity. This example highlights how sustainable approaches to chemistry open up new possibilities due to their diverse ways of providing mass or energy transport.

Clearly, the future of sustainable fertilizers appears promising, but this may not be all. A recent perspective from MacFarlane and coauthors argues that beyond merely feeding the world, ammonia can be the highly practical energy carrier that is central to a so-called ammonia economy.6 To transition towards said economy, a multi-stage plan is proposed which starts from carbon capture at current Haber-Bosch plants and ultimately ends with a global shift to electrochemical ammonia synthesis. If the studies discussed above are of any indication, though, the final stage may well make use of the incessant grind of mechanochemistry. In the end, whether our ammonia comes from a ball mill or an electrode, the bottom line does not change: green methodologies are poised to not only feed our world but also galvanize it.

References

(1)         How many people does synthetic fertilizer feed? https://ourworldindata.org/how-many-people-does-synthetic-fertilizer-feed (accessed 2022 -01 -17).

(2)         Hattori, M.; Iijima, S.; Nakao, T.; Hosono, H.; Hara, M. Solid Solution for Catalytic Ammonia Synthesis from Nitrogen and Hydrogen Gases at 50 °C. Nat Commun 2020, 11 (1), 1–8. https://doi.org/10.1038/s41467-020-15868-8.

(3)         Han, G.-F.; Li, F.; Chen, Z.-W.; Coppex, C.; Kim, S.-J.; Noh, H.-J.; Fu, Z.; Lu, Y.; Singh, C. V.; Siahrostami, S.; Jiang, Q.; Baek, J.-B. Mechanochemistry for Ammonia Synthesis under Mild Conditions. Nat. Nanotechnol. 2021, 16 (3), 325–330. https://doi.org/10.1038/s41565-020-00809-9.

(4)         Reichle, S.; Felderhoff, M.; Schüth, F. Mechanocatalytic Room-Temperature Synthesis of Ammonia from Its Elements Down to Atmospheric Pressure. Angewandte Chemie International Edition 2021, 60 (50), 26385–26389. https://doi.org/10.1002/anie.202112095.

(5)         Paál, Z.; Ertl, G.; Lee, S. B. Interactions of Potassium, Oxygen and Nitrogen with Polycrystalline Iron Surfaces. Applications of Surface Science 1981, 8 (3), 231–249. https://doi.org/10.1016/0378-5963(81)90119-7.

(6)         MacFarlane, D. R.; Cherepanov, P. V.; Choi, J.; Suryanto, B. H. R.; Hodgetts, R. Y.; Bakker, J. M.; Ferrero Vallana, F. M.; Simonov, A. N. A Roadmap to the Ammonia Economy. Joule 2020, 4 (6), 1186–1205. https://doi.org/10.1016/j.joule.2020.04.004.

Sandalwood and Santalols – A Toast to a Legendary Fragrance

By Brian Tsui, PhD candidate in the Morris Group at the University of Toronto and Website Coordinator for the GCI

Since the earliest civilizations, perfumes have been used by humans to impart pleasant aromas to themselves and their environment. Until recently, most perfumes were derived from natural sources such as natural oils, flowers, and herbs. Perfumes of today are complex, composed of many natural and synthetic chemicals dissolved in a solvent, mainly water and ethanol, to the appropriate concentration. One of the most legendary chemical components can be found in sandalwood, which is a class of slow-growing woods found primarily in south and southeast Asia. Sandalwood is often stated to be one of the most expensive woods in the world due to its oil having the unusual property of retaining its woody and spicy aroma for decades. Some well-known fragrances that contain sandalwood oil are Crystal Noir by Versace and Hypnotic Poison by Dior (Figure 1). In addition to being used in various religions from Buddhism to Zoroastrianism, sandalwood oil has been used in Ayurvedic medicine for the treatment of somatic and mental disorders.3

Figure 1. Examples of fragrances containing sandalwood oil.1,2

Combined with the near-monopoly on the sandalwood industry by the Indian government, which was only relaxed in the late 1990s, it is not surprising that demand has outstripped supply. On the demand side, China alone is expected to account for 20,000 tonnes of sandalwood by 2025. Each harvestable sandalwood tree only produces roughly 600-700 mL of sandalwood oil, which corresponds to around $2,000 of sandalwood oil per tree. Sustainably sourced sandalwood can easily double the global market value. This high profitability has led other countries to enter the sandalwood industry, such as Australia. TFS Corp is a leading Australian producer that is expected to increase the production of sandalwood to 10,000 tonnes to meet future demands.4 The main supply challenge is that it can take up to 15 years until sandalwood is mature enough to be harvested for its oils. The slow maturation rate of sandalwood is thus heavily susceptible to disease and increasing impacts of climate change. The extraction process is also destructive by uprooting the entire tree to be physically broken down before steam distillation. Until new sandalwood farms reach harvest maturity, synthetic chemists are tasked with finding routes to this fragrance oil.

Figure 2. Main components of sandalwood oil.

Early research in 1914 by V. Paolini and Laura Vivizia at the University of Rome detailed the isolation of sandalwood oil into pure components α-santalol and β-santalol (Figure 2).5 Not to be confused for the laugh of the jolly old man who may have descended your chimney this holiday season, santalols belong to a class of sesquiterpenes, which in turn are a class of terpenes comprising of three isoprene units. It was found that the α isomer comprised roughly 55% of sandalwood oil, with the β isomer making up roughly 20%. The α isomer is purported to have most of sandalwood oil’s therapeutic properties such as increased attentiveness, anticancer properties, and topical anti-inflammation.3,6 In contrast, the β isomer provides the woody and spicy aroma characteristic of sandalwood oil. Later in 1970, Elias J. Corey and coworkers at Harvard University published the first total synthesis of α-santalol in 11.3% yield starting from (+)-3-bromocamphor (Figure 3a).7,8 Much later in 2009, Charles Fehr and coworkers at Firmenich SA reported the first total synthesis of β-santalol in 31.5% yield starting from crotonaldehyde and cyclopentadiene (Figure 3b).9 In more recent and scalable work by BASF in 2020, a fermentation process with Rhodobacter sphaeroides using cornstarch-derived sugars from European corn affords α-santalol and β-santalol in a similar ratio compared to that of natural sandalwood oil.10 Isobionics, a Dutch biotech firm focused on fermentation of aromatic compounds and acquired by BASF in 2019, demonstrates the viability of sandalwood oil production year-round with minimal waste and cost, without worrying about destructive cultivation of old sandalwood forests.

Figure 3. Retrosynthetic routes to α-santalol and β-santalol.

With global demand only increasing for this valuable oil, chemists are poised to tackle this problem to meet the religious, fragrance, and medicinal needs of today’s society. One thing is for certain: human nature will no doubt value “natural” sandalwood oil over “synthetic” sandalwood oil, even if the two products are chemically identical. Whether by increasing the cultivation of sustainable sandalwood forests for a natural product or fermentation of cheap and renewable feedstocks to afford synthetic sandalwood oil, scientists are working to ensure that these chemicals will be available to those who can stomach the cost that its unique properties demand.

References

  1. Versace. https://www.versace.com/eu/en/women/accessories/fragrances/crystal-noir/ (accessed Dec 13, 2021)
  2. Dior. https://www.dior.com/en_ca/products/beauty-Y0063401-hypnotic-poison-eau-de-toilette (accessed Dec 13, 2021)
  3. Heuberger, E.; Hongratanaworakit, T.; Buchbauer, G. Planta Med. 2006, 72, 792–800
  4. Quintis Sandalwood. https://www.quintis.com.au/ (accessed Dec 12, 2021)
  5. Paolini, V.; Divizia, L. Atti R. Accad. Lincei 1914, 23, 226-230
  6. Bommareddy, A.; Brozena, S.; Steigerwalt, J.; Landis, T.; Hughes, S.; Mabry, E.; Knopp, A.; VanWert, A. L.; Dwivedi, C. Nat. Prod. Res. 2019, 33, 527-543
  7. Corey, E. J.; Chow, S. W.; Scherrer, R. A. J. Am. Chem. Soc. 1957, 79, 5773-5777
  8. Corey, E. J.; Kirst, H. A.; Katzenellenbogen, J. A. J. Am. Chem. Soc. 1970, 92, 6314-6320.
  9. Fehr, C.; Magpantay, I.; Arpagaus, J.; Marquet, X.; Vuagnoux, M. Angew. Chem. Int. Ed. 2009, 48, 7221-7223
  10. Bettenhausen, C. Chemical and Engineering News. https://cen.acs.org/business/5-new-technologies-making-impact/98/i46#Case-study-4-Making-sandalwood-oil-without-sandalwood-trees (accessed Dec 11, 2021)

What are Organic Chemists doing to save the World?

By Alessia Petti, Ph.D. candidate in electrosynthesis at the University of Greenwich, guest blog writer

According to the most recent UN report, the last decade (2011-2020) was the warmest on record with carbon dioxide emissions reaching 148 percent of preindustrial levels in 2019.[1] The demand for change is urgent and, as recently emphasized at the COP26 in Glasgow, the time to act is shorting. Given the global nature of the problem, we should all ask ourselves what we are doing/can do to save the Earth. With this post, we intend to answer this question from an organic chemist perspective by summarizing the most significant developments in the field that enable waste reduction and guide us towards a sustainable future.

Figure 1: Earth Warming Up. Credits to: https://www.un.org/en/climatechange/what-is-climate-change

3 ways of fighting Global Warming in Organic Chemistry

  1. Beyond Thermochemical Activation: Enlightened Syntheses

Organic reactions often require thermochemical conditions to take place. Nevertheless, these conditions become incredibly energy-consuming when transferred to large-scale industrial processes. Energy waste is often associated with material waste, especially in the case of conventional redox reactions wherein stoichiometric quantities of redox reagents are necessary. Electrochemistry and photochemistry represent two alternative ways of activating organic molecules in an almost reagent-less fashion. Inexpensive electricity or light, derived from renewable energy sources, allows obtaining extremely selective electron transfers[2,3] while unlocking unprecedented reactivities. Within this context, Britton’s group (Simon Fraser University) in collaboration with Merck reported a photocatalytic method for the C-H fluorination of γ-fluoroleucine, a key intermediate in the preparation of the osteoporosis drug Odanacatib (Figure 2).[4]

Figure 2: Photocatalytic C-H fluorination of γ-fluoroleucine derivative.[5]

While previous fluorination protocols involved a multistep synthesis and the use of hazardous reagents such as hydrofluoric acid, this pathway affords the desired product directly from the unprotected amino acid in high selectivity via UV-irradiation of a decatungstate-catalyst. High productivities were also achieved when translating the reaction in flow (90% yield, 45 g after 2 h of residence time). Although using minimum amounts of metal catalysts represents a substantial improvement, redox reactions can be performed without any catalyst at all. This is the case of direct electrochemical reactions such as the anodic synthesis of ureas[6] realised by Lam’s group (University of Greenwich) (Figure 3). In this work, the carbonyl derivatives are accessed at room temperature by in situ generation of isocyanates followed by the one-pot addition of an amine.

Figure 3: Anodic synthesis of ureas.[6]

Electrolysis is achieved in the presence of cheap carbon graphite electrodes and without using any supporting electrolyte. Additionally, when performing the reaction in flow, no purification is required with the urea products formed in only six minutes (0.3 mmol scale).

2. Cleaner solvents by following Nature’s lead

Solvents have a crucial role in most organic transformations. However, most of those currently used in organic chemistry are petroleum-based and pose serious risks due to their flammability, carcinogenicity, and explosivity. Moreover, their persistence in soils and aquatic ecosystems has a major detrimental impact on the environment.[7] On the other hand, using water as the main solvent represents a cheap, safe, and environmentally benign alternative. Additionally, nature has shown us over a billion years that achieving complex transformations in this medium is perfectly doable. Driven by these considerations, Professor Lipshutz (University of California, Santa Barbara) has developed new synthetic methods using water as a large reaction medium in combination with micellar catalysis. One of his latest works involves a Migita cross-coupling formation of thioethers performed in recyclable water in presence of the surfactant (TPGS-750-M) and low levels of Ni catalyst (Figure 4).[8]

Figure 4: Migita-Like C−S Cross-Couplings in Recyclable Water.[8]

Despite these encouraging results, we are still far from reaching nature’s perfection. For instance, the water along with additives recovered at the end of the process must be treated as “wastewater” and therefore recycled. Aspects involving the toxicity and biodegradability of the surfactant must also be considered.

3. Turning waste into gold

Finally, organic chemistry is often associated with polymer synthesis. Out of the 381 million tonnes of plastic waste per year, only 9% of single-use plastics are recycled.[9,10] This 9% is mostly recycled via mechanical methods which would inevitably convert the polymer into lower-quality materials. Furthermore, many polymers cannot be recycled via mechanical processes meaning that these materials are destined for incineration. In an effort to invert this trend, Professor McNeil (University of Michigan) is exploring the possibility of chemical recycling. In her recent publication[11], a new and mild route for recycling the acrylic-based superabsorbent material used in diapers is disclosed. The transformation into commercially relevant pressure-sensitive adhesives (PSAs) relies first on acid-catalyzed hydrolysis followed by an optional chain-shortening via sonication and lastly, esterification driven by hydrophobicity (Figure 5).

Figure 5: Syntheses of pressure-sensitive adhesives from petroleum feedstocks (industrial approach) compared to waste diaper-based feedstock.[11]

Life cycle assessments conducted on the adhesives synthesized via this approach outperformed the petroleum-derived counterparts on nearly every metric including carbon dioxide emissions and cumulative energy demand.

To conclude, each scientist and innovator has the power to influence our planet’s tomorrow. Hence, start experimenting and be the change that you want to see in the world!

References

[1]        “Climate Reports | United Nations,” can be found under https://www.un.org/en/climatechange/reports, n.d.

[2]        G. E. M. Crisenza, P. Melchiorre, Nat. Commun. 2020, 11, 1–4.

[3]        M. Yan, Y. Kawamata, P. S. Baran, Chem. Rev. 2017, DOI 10.1021/acs.chemrev.7b00397.

[4]        S. D. Halperin, D. Kwon, M. Holmes, E. L. Regalado, L. C. Campeau, D. A. Dirocco, R. Britton, Org. Lett. 2015, 17, 5200–5203.

[5]        G. E. M. Crisenza, A. Faraone, E. Gandolfo, D. Mazzarella, P. Melchiorre, Nat. Chem. 2021, 13, 575–580.

[6]        A. Petti, C. Fagnan, C. G. W. van Melis, N. Tanbouza, A. D. Garcia, A. Mastrodonato, M. C. Leech, I. C. A. Goodall, A. P. Dobbs, T. Ollevier, K. Lam, Org. Process Res. Dev. 2021, DOI 10.1021/acs.oprd.1c00112.

[7]        M. Cortes-Clerget, J. Yu, J. R. A. Kincaid, P. Walde, F. Gallou, B. H. Lipshutz, Chem. Sci. 2021, 12, 4237–4266.

[8]        T.-Y. Yu, H. Pang, Y. Cao, F. Gallou, B. H. Lipshutz, Angew. Chemie Int. Ed. 2021, 60, 3708–3713.

[9]        “100+ Plastic in the Ocean Statistics & Facts (2020-2021),” can be found under https://www.condorferries.co.uk/plastic-in-the-ocean-statistics, n.d.

[10]     “The world’s plastic problem in numbers | World Economic Forum,” can be found under https://www.weforum.org/agenda/2018/08/the-world-of-plastics-in-numbers, n.d.

[11]     P. T. Chazovachii, M. J. Somers, M. T. Robo, D. I. Collias, M. I. James, E. N. G. Marsh, P. M. Zimmerman, J. F. Alfaro, A. J. McNeil, Nat. Commun. 2021, 12, 1–6.

Gas-to-protein agriculture: decoupling food from environment

By Eloi Grignon, Ph.D. student, Member-at-Large for the GCI

Faced with a worsening climate crisis and growing food insecurity, humans have begun to produce food from the air. While you’d be forgiven for assuming this plot to be that of an Asimov story, it is, in fact, the reality that several start-ups envision for the future of agriculture. Indeed, a wave of firms have developed gas-to-protein technologies that employ bacteria to convert feed gases into an edible flour.

In truth, none of the technologies designed to date rely solely (if at all) on air. For instance, Solar Foods, a Finnish biotech company, combines carbon dioxide from the air with green (i.e. not derived from fossil fuels) hydrogen and water to feed a carefully selected bacterium. The result of this fermentation is their proprietary Solein protein, which they currently produce at a rate of 1 kg per day.1 Others in the gas-to-protein industry have developed their fermentation processes around different gases: Calysta uses methane supplied by the energy giant BP while Lanza Tech relies on the waste carbon monoxide generated by a nearby steel plant.1

Solar Foods’ recipe for their Solein protein. From [5].

The synthesized proteins are generally viewed and marketed as alternatives to other plant-based proteins, such as those derived from soy, whose cultivation is land-intensive and can come at the cost of intense deforestation.2 Here, gas-to-protein agriculture has the tantalizing potential to produce food on similar scales while requiring only a fraction of the area. A 2018 study estimated that widespread adoption (roughly 10-20% market share) of gas-to-protein could reduce farmland area by 6% and associated GHG emissions by 7%.3

Land intensity of various protein sources. From [4].

Gas-to-protein agriculture may also help phase out animal-based proteins. One suitable target for replacement is fishmeal, the powder obtained from drying and grinding the bones and offal of commercial fisheries’ by-catch.  Fishmeal, which is used as the primary source of protein for farm-raised fish, consumes approximately one quarter of the global wild fish catch and is strongly linked with the depletion of aquatic environments and collapse of local fisheries.1 As a more sustainable alternative, Calysta produces a bacteria-sourced protein with all the amino acids required to feed farmed fish. The potential impact is huge: Calysta’s CEO claims that the presence of a 100,000-tonne plant of synthetic protein can allow 500,000 wild fish to remain in the ocean.1

The boons of gas-to-protein agriculture are pushed to truly stupendous heights when CO2-consuming processes are employed. According to Solar Foods, the operation’s economic use of energy coupled with its inherent carbon sequestration could translate to a protein with only 1% of the carbon footprint of its plant- and animal-derived counterparts.1

Beyond the increased protection of forest and aquatic ecosystems along with huge water and energy savings, gas-to-protein agriculture has other, more intangible advantages. For instance, the liberation of food production from environmental dependence means that the protein’s annual tonnage need not be subject to environmental crises or day-to-day weather. Moreover, scaling production up or down can be achieved far more easily when no marginal land or animals come into the equation.

Although there is great promise for gas-to-protein firms to gain an established foothold, there remain several economic hurdles impeding widescale production. Chief among these is the high cost of green hydrogen – a key ingredient of many firms’ protein recipe. Green hydrogen is produced from the electrolysis of water and, as such, its price is contingent on the supply of low-cost electricity. It is hoped that the economies of scale associated with the advent of renewables will lower the price of electricity sufficiently to render gas-to-protein agriculture the economically favourable option. The balance may also be tipped in favour of gas-to-protein agriculture if alternative, non-monetary costs, such as those of land and wildlife, are factored into consumer decision-making.

The first agricultural revolution saw us take mastery of our environment and irreversibly change the course of human history. If gas-to-protein agriculture is to become a mainstay, could we now, 12 millennia later, be on the brink of witnessing an equally important turning point?

References

[1] Scott, A. (2020). Food from the air. CHEMICAL & ENGINEERING NEWS98(35), 18-21.

[2] Phillips, D. (2020). The Cerrado: how Brazil’s vital ‘water tank’ went from forest to soy fields. https://www.theguardian.com/environment/2020/nov/25/the-cerrado-how-brazils-vital-water-tank-went-from-forest-to-soy-fields

[3] Pikaar, I., De Vrieze, J., Rabaey, K., Herrero, M., Smith, P., & Verstraete, W. (2018). Carbon emission avoidance and capture by producing in-reactor microbial biomass based food, feed and slow release fertilizer: potentials and limitations. Science of the Total Environment644, 1525-1530.

[4] https://www.calysta.com/feedkind/. Accessed February 20, 2021.

[5] https://solarfoods.fi/impact/#bioprocess. Accessed February 27, 2021.

A Materials Chemistry Student’s Take on Fast Fashion

By Hana El-Haddad, Secretary for the GCI

It is April 2020 and you are scrolling through your endless TikTok “for you” page when you stumble across a video informing you about so-called “fast fashion”. The words “affordable” and “toxic” stick with you because they are not used to describe or advertise fashion, and yet you wonder how you have never heard of that side of the fashion industry.

Hi, my name is Hana and I will provide you with a quick perspective on what I think is one of the most overlooked environmental problems of our modern world.

What is Fast Fashion?

In the past decade, brands have taken to widening their production lines by mass-producing clothes and continuously cycling fashion trends through the use of cheap labour and cheap materials. In simpler terms, mass-production can be defined by the shipment of new styles received daily (e.g. H&M and Forever 21) or when a retailer introduces 400 styles a week on its website (e.g. Topshop). Fast fashion is mainly aimed at young women whose dependence on social media can persuade them to think that they are behind on trends as soon as they see styles being worn by influencers and celebrities. An example of a fast fashion brand boosted by social media is Shein, so trendy and yet so unbelievably cheap. The need to shop for the latest trend is facilitated by the garment’s affordability, thus catering to young people’s disposable income. One of the most alarming concerns associated with fast fashion and the rapid cycling of trends is the incredibly high yield of textile waste, which often ends up in a landfill. According to the EPA Office of Solid Waste, the average American disposes of up to 68 pounds of clothing and textiles per year.1 Want a better picture? If the population of the United States is comprised of 328 million individuals, the theoretical annual number of textile waste going to the landfill would rise to a whopping 22300 million pounds – the weight of 2 million adult elephants!

Figure 1. A non-comprehensive list of fast fashion retailers2.

The double-edged sword of democratization

As journalist Lucy Siegle puts it, “fast fashion isn’t free. Someone somewhere is paying.”3 Siegle is not wrong: Chinese workers make as little as 12-18 cents per hour, according to figures from the U.S. Labour Committee. With the increasing competition between emerging economies, these workers will be receiving lower wages and will start working in even poorer conditions, resulting in a net decrease in production costs. Fast fashion brands hold their manufacturing factories in low to middle-income countries which significantly lowers production costs. As a result, low to middle-income countries produce 90% of the world’s clothing.1

A bit of the chemistry explained

As a materials science student, I find that a big part of this problem lies in the chemistry of the textiles used. On one hand, antibacterial agents that are added to textiles can lead to antibiotic resistance in humans, according to a Swedish Chemicals agency. On the other hand, dyes contain toxic chemicals that bio-accumulate, causing the spread of diseases and increase the risk of cancer among individuals in various communities (and that is not considering these chemicals’ effects on factory workers)!4 Brian Tsui, a fellow GCI member, further discusses the chemical aspect of this problem in his blog post titled, “Textiles True Colours: How Sustainable are they?” I would highly recommend giving it a read if you wish to know more about the fashion industry’s use of chemicals in dyes.5 Although there are numerous ways to approach this, a good way to start would be ensuring that the materials safety data sheets of industrial chemicals be more comprehensive and catered to the non-chemist so that the general public, as well as manufacturers, have a better understanding of the chemicals and textiles used. More importantly, meaningful communication between materials chemists, governments, and retail giants should be practiced to ensure strict and uncompromising regulations for textile production.6

Figure 2. Environmental impacts of different textiles7.

What is slow fashion?

This concept is likely intuitive now after I explained fast fashion; but to reiterate, slow fashion is the decrease in clothing consumption as a consequence of an increase in garment lifetime. You might be asking yourself whether the solution lies in the hands of luxury brands since we can check off the aspect of an increase in garment lifetime. Surprisingly, this not the case! Luxury retailers have very similar shortcomings to other fast fashion chains, where some manufacturers are based in low to middle-income countries and labourers work under questionable environments. Some luxury retailers also hold large unsold inventories that go to (you guessed it!) landfills. The advantageous side of shopping luxury brands, however, is that they typically provide longer-lasting items by using higher quality fabrics, second-hand sales, and viable repair services.8

So, what can you do?

When I was first researching this topic, I was quite overwhelmed by how deeply entrenched consumerist patterns are in our societies. I have noticed, though, that the solution to the problem of fast fashion really does lie within the hands of a more environmentally conscious consumer. If this weren’t the case, Patagonia would not have switched to recycling plastics bottles to use them in fabrics and Versace would not have used corn by-products to make Ingeo, a more sustainable fabric.1 I have compiled a list of small and easy steps we could all take towards building a more sustainable wardrobe:

  1. Buy less!
    A rule of thumb is to ask yourself if you are head-over-heels in love with the clothing item you are contemplating buying. If you are, great! Now ask yourself if you will have the opportunity to wear it on a biweekly basis!
  2. Wash your clothing items less
    That is not to say that you should not wash a dirty clothing item! Wash garments only when needed and according to their clothing label. Not only will this allow your clothes to last longer, but it will also reduce your carbon footprint.
  3. Shop second-hand!
    I cannot stress this enough. I always take my friends thrift-shopping whenever possible. Thrifting saves clothes from landfills and reduces your carbon footprint. If you are concerned with its trendiness, you can rest assured that thrifting gives you timeless elegance (fashion trends also do cycle, as I mentioned earlier!).
  4. Shop local
    Many have been preaching supporting local businesses due to the COVID-19 pandemic and you are probably sick of it, but try to give it a shot! Most local businesses actually sell sustainable clothing items that do not take advantage of cheap labour and do not rely on heavily manufactured dyes. Not only is this an easy way to prevent your local family-owned business from closing down, but you would also be saving the environment.
  5. Shop luxury brands for “essentials”
    Seems counterintuitive but splurging on that one designer piece that would last you 10-20 years is definitely more worthwhile than spending on a garment you would be paying more money to replace every few years.
  6. Donate/ Sell your clothes!
    By donating, you are increasing the lifetime of your garment and allowing someone else to flaunt a unique garment with its very own pre-loved charm. Selling your clothes is also a great way to start your own business by selling your more expensive clothing items. A great way to start selling clothes is through apps like Depop where you can list your clothing items and price them as you want.

If you have read through my blog post thus far, thank you and I trust that you have learned something new! I also hope you realize that it is now your responsibility to carry this message forward by practicing sustainable consumption and spreading awareness about sustainable fashion in your community.

References

  1. Claudio, L. Waste Couture: Environmental Impact of the Clothing Industry. Environmental Health Perspectives 2007115(9). 
  2. Segura, A. Mass-market fashion retailers. https://fashionretail.blog/2019/04/22/mass-market-fashion-retailers/.
  3. Stanton, A. What Is Fast Fashion, Anyway? https://www.thegoodtrade.com/features/what-is-fast-fashion.
  4. KEMI Swedish Chemicals Agency. Chemicals in textiles – Risks to human health and the environment. Report from a government assignment. Report 6/14. kemi.se https://www.kemi.se/global/rapporter/2014/rapport- 6-14-chemicals-in-textiles.pdf
  5. GreenChemUofT. Textiles True Colours: How Sustainable are they? https://greenchemuoft.wordpress.com/2020/03/24/textiles-true-colours-how-sustainable-are-they/.
  6. Wang, Z.; Cousins, I. T.; Scheringer, M.; Hungerbühler, K. Fluorinated Alternatives to Long-Chain Perfluoroalkyl Carboxylic Acids (PFCAs), Perfluoroalkane Sulfonic Acids (PFSAs) and Their Potential Precursors. Environment International 201360, 242–248. 
  7. Niinimäki, K.; Peters, G.; Dahlbo, H.; Perry, P.; Rissanen, T.; Gwilt, A. The Environmental Price of Fast Fashion. Nature Reviews Earth & Environment 20201 (4), 189–200. 
  8. Ducasse, P.; Finet, L.; Gardet, C.; Gasc, M.; Salaire, S. Why Luxury Brands Should Celebrate the Preowned Boom. https://www.bcg.com/publications/2019/luxury-brands-should-celebrate-preowned-boom.aspx.

Upgrading Health: Using Supercritical CO2 to Increase Drug Efficacy

By Shreya Kanade, GCI member-at-large

An efficient way to administer pharmaceutical drugs to a patient is through a tablet. The drugs are measured and coated in a plastic that is broken down when the drugs are injected into the person, and the drug is absorbed into the bloodstream and transported to the tissue it acts upon. The traditional processes of packaging drugs in these plastics, however, often require the usage of high temperatures and solvents that can be harmful. For example, many volatile organic compounds like benzene and chloroform are used. There is the potential for some of the solvent to remain as a residual impurity after the manufacturing process and can be toxic to the patient or the environment. These materials also need specific management to prevent them from escaping into the atmosphere. Even more, the process of coating the drugs sometimes reduces the efficiency of the dose; for instance, high temperatures and volatile solvents can cause up to a 50% drop in efficacy (1).

At the University of Nottingham, Professor Steve Howdle and his team have used green chemistry techniques to design a plastic coating that does not decrease drug efficacy. The plastic degrades in the body at a controlled rate, releasing the drug into the patient over a specific period.

Professor Howdle uses supercritical fluids (Figure 1), specifically supercritical carbon dioxide (sc-CO2), instead of the conventional benzene and chloroform solvents typically used (1). A supercritical fluid has properties of both liquids and gases at a certain pressure and at around room temperature. Using sc-CO2, conventional solvents are not required and biodegradable plastics can be used to make polymers that coat the drugs before being administered to the individual. Furthermore, it has been demonstrated that using sc-CO2 allows for the plasticization of these polymers near room temperature, which means that the drug activity is unaffected. At room temperature, the plastics are solid but when exposed to high pressure (i.e. the critical pressure of sc-CO2), they liquify and allow for the drugs to be mixed in. Once in the blood, the polymers degrade slowly over days, allowing for a steady release of the drug into the patient. This maximizes the effect of the medicine and reduces the duration of the patient’s treatment regime. Polymers can degrade at different rates and the rate of degradation can be matched with the administered drug that best suits the patient’s needs.

Figure 1. The different phases of carbon dioxide with varying temperature and pressure (2).

              These techniques can allow patients to receive medications that were previously unavailable due to the drugs being too delicate or too reactive to withstand the traditional methods of coating. Because proteins are so sensitive, they are not able to withstand elevated temperatures or strong solvents; with Dr. Howdle’s techniques, however, patients will soon have access to these treatments. Furthermore, because these processes do not include volatile organic solvents, there are no residues that could potentially be harmful to the patients or the environment.

Works Cited

Monomer Spotlight: Multifunctional and Renewable Itaconic Acid

By Nina-Francesca Farac, Ph.D. student, Social Media Coordinator and Blog Coordinator for the GCI

            As chemists and material scientists strive to create a sustainable chemical industry, chemical building blocks derived from renewable resources have become a research necessity1. In 2004, the U.S. Department of Energy reported 12 building blocks attainable from biomass which have high potential for high-value chemicals or materials.2–4 One of the listed biorenewable building blocks is itaconic acid (IA). IA is an inexpensive, non-toxic, and readily available compound produced by the fermentation of glucose or other biomass sources such as corn, rice, or lignocellulosic feedstock.1,2 Importantly, IA is produced through an industrially scaled glucose fermentation process with an estimated global production of 80,000 tons/year and a price of around 2 USD/kg.5 Given this compound’s potential to become economically competitive with petroleum-based sources, its manufacturing capacity is expected to grow at a rate of 5.5% each year between 2016 and 2023.5,6

IA or methylene succinic acid has a trifunctional structure with two carboxylic acid groups and an α,β-unsaturated double bond in the backbone (1, Figure 1). These functional groups make IA a promising monomer for a variety of polymeric reactions.5,7,8 The polymerization of IA and its derivatives has been extensively studied to access a wide range of new and renewable advanced materials.  

Figure 1. Chemical structure of itaconic acid (1) and its ester derivatives (2, 3) along with acrylic (4) and methacrylic acid (5).

Most attention has been focused on radical polymerization of IA (Figure 2a) and its various alkyl esters such as dimethyl itaconate (2) and dibutyl itaconate (3) due to their structural similarities to the traditional monomers for poly(meth)acrylates, acrylic acid (4) and methacrylic acid (5). More recently, the step-growth polymerizations of itaconate derivatives have been investigated for the synthesis of numerous polyesters (Figure 2b).5,9

Figure 2. Select polymerization pathways for itaconate.

Several other chemical transformations have been explored to generate interesting materials from IA-derived polymers, such as thermoplastics and thermosets. Nonetheless, researchers argue that a significant amount of chemical space remains unexplored for the synthesis of high-value materials from IA.1 Moreover, several IA-derived polymers tend to have high glass-transition temperatures (Tgs) that limit their application.

In effect, Trotta et al.1 set out to design new polymers from IA and to expand the library of IA-derived renewable materials. Published in ACS Sustainable Chemistry & Engineering in December 2018, Trotta & colleagues were able to synthesize and characterize bio-sourced thermosets and thermoplastics that are almost completely derived from IA and whose mechanical properties are tunable. The authors developed scalable and efficient syntheses of three step-growth monomers from an IA derivative (Figure 3a). These monomers were then used to access functional polyesters that can be used for making thermosets and thermoplastics that are both mechanically and thermally stable (Figure 3b).

Figure 31. (a) Bio-sourced monomers from IA. (b) Bio-sourced thermoplastics and thermosets derived from IA.

1. Synthesis & Characterization of Step-Growth Monomers from IA

First, a saturated diester (MS), a saturated diol (MB), and an unsaturated diester (CS) step-growth monomers were efficiently synthesized from commercially available dimethyl itaconate (DMI), an IA derivative (Figure 3a). The DMI-to-CS transformation was motivated by the instability of DMI itself in step-growth polymerization with diols. A scalable Diels-Alder reaction was carried out to circumvent this issue. The diene of choice was isoprene since it was recently demonstrated that isoprene can be derived from IA10, allowing for the synthesis of a stable monomer (CS) that is made completely from IA.

2. Step-Growth Polycondensation Polymerizations – Synthesis & Characterization

Next, binary (i.e. two-monomer) and ternary (i.e. three-monomer) step-growth polycondensations were carried out to make various amorphous polymers with low Tgs (e.g. -31 to -9 °C) and relatively high molar masses (>10 kg/mol). The low Tgs suggest easier processability and a wider range of applications for these polyesters. Thermogravimetric analysis confirms the relative stability of these polymers, particularly PMBCS (Figure 4) whereby no retro-Diels Alder reaction was observed along the polymer backbone at temperatures above 200 °C.

Figure 4.1 Synthesis of (a) fully unsaturated poly(MB-alt-CS) (PMBCS), (b) fully saturated poly(MB-alt-MS) (PMBMS), and (c) statistical ternary PMBCSx-stat­-PMBMS1-x.

3. IA-Derived Thermosets

By controlling the feed ratio of the CS monomer, the authors produced ternary polyesters with tunable amounts of unsaturation along the polymer backbone. This gave rise to polyesters that can be efficiently cross-linked using thiol-ene click chemistry to generate thermosets. 

To continue with the theme of bio-sourced materials, the authors used a potentially renewable tetrathiol cross-linker (highlighted in purple, Figure 5b), to cross-link the ternary polymer, PMBCSxstat­-PMBMS1-x (Figure 5c).

Figure 5. (a) A model reaction for thiol-ene “click” chemistry on PMBCS. (b) A potentially renewable retro-synthetic route to the tetrathiol cross-linker. (c) Cross-linking reaction of crude PMBCSx-stat­-PMBMS1-x with the tetrathiol cross-linker and DMPA initiator to give IA-derived thermosets.

The authors characterized both the thermal and mechanical properties of the synthesized thermosets. The cross-linking reaction afforded thermosets with slightly higher Tgs than their respective prepolymers, suggesting decreased flexibility of the polymer backbone due to cross-linking. The Young’s modulus (E), which is a measure of a material’s elasticity, was the largest for thermosets with the highest cross-linking densities. It was also observed that these mechanical properties are tunable by varying the molar mass between cross-links.

4. IA-Derived Thermoplastics

Finally, the authors prepared well-defined triblock polymer thermoplastics that can be prepared from IA-derived α-methylene-γ-butyrolactone (MBL)11 (Figure 6), giving thermoplastics that are almost completely derived from IA.

Figure 6.1 Chain extension of HO-PMBMS-OH to give PMBL-PMBMS-PMBL.

Tensile testing data indicate that the MBL chain-extended triblock polymer is indeed thermoplastic. The triblock polymer exhibits ductile tensile properties with a Young’s Modulus and tensile strength far exceeding those of the IA-derived thermosets.

5. Green Metrics

            A sustainable chemical industry not only requires the use of bio-sourced/biorenewable substrates but also relies on safe and energy-efficient synthetic processes that do not generate any additional waste streams. In effect, the authors evaluated the small molecule transformations and polymerizations disclosed above using green metrics12 – measures to quantify the efficiency and/or environmental performance of a chemical process as it relates to the principles of green chemistry.13,14 Isolated yields, atom economies (AEs)15, and process mass intensities (PMIs)16 were reported for select reactions as listed in Table 1.

Table 1. Green metric evaluations of various reactions presented by Trotta et al. aDefined as the percent of the molecular weight of the desired product compared to the molecular weight of all starting reactants. bDefined as the ratio of the mass (in kg) of all the raw material used in the synthesis of the desired product (including all reagents, mass of solvent(s) and other materials such as silica used in purification) to the mass (in kg) of the isolated product.

Most of the small molecule transformations and polycondensations are high yielding with a few exceptions. The low yield of 60% for PMBCS in reaction 4 is attributed to low polymer recovery during the purification by precipitation step.1 For reactions 2 and 3, yields >90% are achievable but on smaller scales; however, the authors desired scalable syntheses, making yields of 82% and 67% acceptable for these purposes.

The AE for addition reactions like reactions 1 and 3 is 100% whereas reactions with undesired byproducts have lower AE. Trotta et al. propose alternative synthetic routes that would result in increased AE for reactions 2, 4, 5, & 6 but these were not explored. Besides, a higher AE does not guarantee a high yielding and low PMI process and such suggestions require further investigation. On the other hand, this emphasizes the challenge scientists are faced when attempting to develop a sustainable process; it is generally difficult to implement all criteria outlined by the principles of green chemistry without having a trade-off somewhere within the process.

The PMI metric nicely showcases the impact of solvent on process efficiency. PMI values closer to 1 indicate a smaller mass of material required to synthesize 1 kg of product.1,16 PMI is low for most reactions listed in Table 1, reflecting little to no use of solvents (i.e. neat conditions) or other reagents during the reaction, workup, and/or purification steps. Comparing reactions 1 through 3, the synthesis of CS has an increased PMI of 12 due to the use of solvent during workup. Similarly, there is a sharp rise in PMI for polymers that are purified by dissolving and precipitating them from solution (reactions 4 and 5). In contrast, polymers that don’t require purification have a significantly lower PMI (reaction 6).

6. Summary  

            Overall, this paper is one of many that demonstrate the growing potential of itaconic acid as a multifunctional and renewable monomer for a wide range of polymerizations. The authors were largely successful in producing new bio-sourced and mechanically (as well as thermally) stable thermosets and thermoplastics from IA-derived materials.

            Although the green metric evaluations identify several sustainable features of the reactions developed by Trotta et al., one aspect that puts into question how ‘green’ the reactions are is the type of catalyst used. Each small molecule transformation (reactions 1 – 3 in Table 1) uses either a platinum group metal or a rare earth metal – both of which are considered critical/endangered elements that are essential for use but subject to supply risk.14 It is noted that the catalyst loading for these reactions is low with amounts below 5 mol% or 5 wt%; however, it is not enough to reduce catalyst use. Complete catalyst recyclability is another factor that should be implemented. On this basis, the authors did show that the Sc(OTf)3 catalyst used in the synthesis of CS can be recovered at a 97% yield prior to distillation of the crude polymer product. The ability to recycle the other catalysts were not mentioned.

            Furthermore, it would have been beneficial if the authors quantified the biorenewable content of their synthesized thermosets and thermoplastics instead of using general statements such as  “almost completely derived from IA”. Other studies investigating the synthesis of polymeric materials from renewable sugar-derived precursors typically state the percentage of biobased content within their resulting materials (e.g. wt% in biorenewable content). For instance, a 2015 study17 described the biobased content of thermosets derived from IA-based polyesterss in the ranges of 78 and 88 wt%. The quantification of biorenewable content would unambiguously validate the work of Trotta et al. and better gauge their impact within the literature.

REFERENCES

(1)      Trotta, J. T.; Watts, A.; Wong, A. R.; Lapointe, A. M.; Hillmyer, M. A.; Fors, B. P. Renewable Thermosets and Thermoplastics from Itaconic Acid. ACS Sustain. Chem. Eng. 2019, 7 (2), 2691–2701.

(2)      Noordzij, G. J.; Van Den Boomen, Y. J. G.; Gilbert, C.; Van Elk, D. J. P.; Roy, M.; Wilsens, C. H. R. M.; Rastogi, S. The Aza-Michael Reaction: Towards Semi-Crystalline Polymers from Renewable Itaconic Acid and Diamines. Polym. Chem. 2019, 10 (29), 4049–4058.

(3)      Werpy, T.; Petersen, G. Top Value Added Chemicals from Biomass Volume I – Results of Screening for Potential Candidates from Sugars and Synthesis Gas; 2004.

(4)      Bozell, J. J.; Petersen, G. R. Technology Development for the Production of Biobased Products from Biorefinery Carbohydrates—the US Department of Energy’s “Top 10” Revisited. Green Chem. 2010, 12 (4), 539–555.

(5)      Robert, T.; Friebel, S. Itaconic Acid – a Versatile Building Block for Renewable Polyesters with Enhanced Functionality. Green Chem. 2016, 18 (10), 2922–2934.

(6)      Transparency Market Research, Market Report Itaconic Acid, 2015; 2015.

(7)      Geilen, F. M. A.; Engendahl, B.; Harwardt, A.; Marquardt, W.; Klankermayer, J.; Leitner, W. Selective and Flexible Transformation of Biomass-Derived Platform Chemicals by a Multifunctional Catalytic System. Angew. Chemie – Int. Ed. 2010, 49 (32), 5510–5514.

(8)      Medway, A. M.; Sperry, J. Heterocycle Construction Using the Biomass-Derived Building Block Itaconic Acid. Green Chem. 2014, 16 (4), 2084–2101.

(9)      Kumar, S.; Krishnan, S.; Samal, S. K.; Mohanty, S.; Nayak, S. K. Itaconic Acid Used as a Versatile Building Block for the Synthesis of Renewable Resource-Based Resins and Polyesters for Future Prospective: A Review. Polym. Int. 2017, 66 (10), 1349–1363.

(10)    Abdelrahman, O. A.; Park, D. S.; Vinter, K. P.; Spanjers, C. S.; Ren, L.; Cho, H. J.; Zhang, K.; Fan, W.; Tsapatsis, M.; Dauenhauer, P. J. Renewable Isoprene by Sequential Hydrogenation of Itaconic Acid and Dehydra-Decyclization of 3-Methyl-Tetrahydrofuran. ACS Catal. 2017, 7 (2), 1428–1431.

(11)    Trotta, J. T.; Jin, M.; Stawiasz, K. J.; Michaudel, Q.; Chen, W. L.; Fors, B. P. Synthesis of Methylene Butyrolactone Polymers from Itaconic Acid. J. Polym. Sci. Part A Polym. Chem. 2017, 55 (17), 2730–2737.

(12)    Tobiszewski, M.; Marć, M.; Gałuszka, A.; Namies̈nik, J. Green Chemistry Metrics with Special Reference to Green Analytical Chemistry. Molecules 2015, 20 (6), 10928–10946.

(13)    Tang, S. L. Y.; Smith, R. L.; Poliakoff, M. Principles of Green Chemistry: Productively. Green Chem. 2005, 7 (11), 761–762.

(14)    Dubé, M. A.; Salehpour, S. Applying the Principles of Green Chemistry to Polymer Production Technology. Macromol. React. Eng. 2014, 8 (1), 7–28.

(15)    Jiménez-González, C.; Constable, D. J. C.; Ponder, C. S. Evaluating the “Greenness” of Chemical Processes and Products in the Pharmaceutical Industry—a Green Metrics Primer. Chem. Soc. Rev. 2012, 41 (4), 1485–1498.

(16)    Jiménez-González, C.; Ponder, C. S.; Broxterman, Q. B.; Manley, J. B. Using the Right Green Yardstick: Why Process Mass Intensity Is Used in the Pharmaceutical Industry to Drive More Sustainable Processes. Org. Process Res. Dev. 2011, 15 (4), 912–917.

(17)    Dai, J.; Ma, S.; Wu, Y.; Han, L.; Zhang, L.; Zhu, J.; Liu, X. Polyesters Derived from Itaconic Acid for the Properties and Bio-Based Content Enhancement of Soybean Oil-Based Thermosets. Green Chem. 2015, 17 (4), 2383–2392.

The Looming Problem of Lithium-Ion Battery Waste

By Eloi Grignon, Ph.D. student, Member-at-Large for the GCI

Since their commercialization in 1991, lithium-ion batteries (LIBs) have gradually come to pervade our daily lives. Their ubiquity is achieved through our phones and laptops (you are likely reading these words via energy supplied by a LIB), where they are used to power not only our communication with one another, but also the myriad other tasks that we have come to delegate to our devices. Increasingly, LIBs are powering how we move, too, as is evidenced by the several million battery electric vehicles already on the road.1 With the production of electric vehicles set to skyrocket – the British and French governments have already pledged to ban sales of fossil-powered vehicles by 2040 – and the possibility of using LIBs for storage of grid electricity, it is clear that LIBs are not going anywhere, either.2 Indeed, spent batteries are expected to be generated at a rate of 2 million metric tons per year by 2030.3

And yet, there is no clear idea of what is to happen to these batteries once they’ve served their purpose. Currently, fewer than 5% of LIBs in the US and Europe are recycled while the rest end up in landfills.3

Since a LIB is densely comprised of several costly metals (Figure 1), it is fair to liken used batteries to enriched ore.3 It follows, then, that complete disposal of millions of metric tons of such a material represents a tremendous waste.

Figure 1.

Figure 1. Breakdown of LIB constituents. From Ref [3].

Recycling could curb the waste by salvaging this ‘ore’ and supplying it to LIB manufacturers at a cheaper price than that of virgin materials, thereby reducing LIB cost. Moreover, less of the material would have to be mined and treated in the first place. This is especially important when considering the impacts of both processes: mining has obvious environmental consequences while ore treatment is typically energy-intensive and can release harmful gases such as SOx.4 Furthermore, 10-25% of global cobalt production is mined by ‘artisanal’ workers in the DRC, many of whom lack proper wages and equipment. The UNICEF estimated in 2012 that 40,000 children were employed in such mines.5 From this perspective, LIB landfilling has a heavy economic, environmental, and moral opportunity cost attached.

In addition to wastefulness, landfilling LIBs also has direct negative consequences. Over time, the toxic constituents of the LIBs tend to flow into the soil, eventually leaching into the groundwater and accumulating in various organisms. These toxins can make their way up to humans, thus extending the health hazard to people. The harm imposed by discarded LIBs on the environment is not without some degree of irony, as LIBs have long been celebrated as a key cog in the establishment of a greener future. Evidently, this detrimental end-of-life scenario presents an incongruity.

Given the benefits of LIB recycling, it is clear that technical and economic barriers, rather than lack of purpose, are responsible for the poor recycling rates.

One such barrier results from the complicated composition within LIBs, which renders separation and recovery of all components difficult. For instance, smelting can effectively recover the heavy metals nickel, cobalt, and copper but fails to salvage lithium and the electrolyte. While hydrometallurgical (chemical leaching) methods can recover more components, they necessitate acids, hydrogen peroxide, and 7 m3 of water per ton of LIB.6 Needless to say, this is not ideal.

Another technical issue is the great variability between LIBs – different manufacturers tend to use different components and so there is no one universal composition (this pertains mainly to vehicles). As such, a recycling firm is at the mercy of its feedstock – for an input collected from many sources, there is no guarantee that 1 ton of batteries will yield a given amount of, say, cobalt.

These issues appear blatant when considering as a counterexample the success story of lead-acid battery recycling, whose simple and standardized composition – about 60% lead – enables an easy recycling process that claims nearly all (99%!) of used batteries.4

The low recycling rates are also due to economic factors. The end-to-end recycling process is energy-intensive and requires many steps, thus increasing costs. A firm operating such a process must carefully assess whether their repurposing protocol is cheap enough to supply materials that are price-competitive with mined materials. Due to the lack of LIB standardization and high volatility of constituent prices, this assessment is far from trivial and the business represents a clear risk. This risk is further exacerbated by the uncertainty of what the future of energy storage may resemble. In the arms race for higher energy density, new technologies arise frequently, thus threatening to render state-of-the-art materials (and so, recycling processes) obsolete.

While the above paragraphs appear rather pessimistic, it should be noted that we are only at the onset of the LIB boom. Indeed, the field of LIB recycling is still gaining traction and it is expected that serious investments will aid in the development of more efficient recycling techniques. To this end, the US DoE (through the $15 million ReCell Center) and the UK-based ReLib project have pledged to fund and support R&D in LIB recycling.3

There is also a clear interest from the private sector as is evidenced by the numerous startup firms currently designing their own protocols, including the Toronto-based company Li-Cycle.7

Another approach to sustainable energy storage is to circumvent the need for recycling breakthroughs altogether by designing the LIB differently from the start. For instance, the use of organic materials that are easily recyclable is increasingly explored for use in devices.1 Not only are these materials favourable in the end-of-life stage, but their production is also cheap, accessible, and environmentally benign.

In any case, scientists, engineers, and policymakers must come together to address the issues caused by LIB landfilling. And quickly, too, because the storm is coming (Figure 2).

Figure 2. A possible scenario for the growth of electric vehicle sales in the next decade. PLDVs = passenger light duty vehicles; LCVs = light commercial vehicles; BEVs = battery electric vehicles; PHEV = plug-in hybrid electric vehicles. From Ref [1].

References

  1. Poizot, P.; Gaubicher, J.;  Renault, S.;  Dubois, L.;  Liang, Y.; Yao, Y. J. C. R., Opportunities and Challenges for Organic Electrodes in Electrochemical Energy Storage. 2020.
  2. Gardiner, J. J. T. G., The rise of electric cars could leave us with a big battery waste problem. 2017, 10.
  3. It’s time to recycle lithium-ion batteries. C&EN Global Enterprise 2019, 97 (28), 29-32.
  4. Gaines, L. J. S. M.; Technologies, The future of automotive lithium-ion battery recycling: Charting a sustainable course. 2014, 1, 2-7.
  5. Frankel, T. C.; Chavez, M. R.; Ribas, J. J. T. W. P., The cobalt pipeline. Tracing the path from deadly hand-dug mines in Congo to consumers’ phones and laptops. 2016, 30.
  6. Larcher, D.; Tarascon, J.-M. J. N. c., Towards greener and more sustainable batteries for electrical energy storage. 2015, 7 (1), 19-29.
  7. https://li-cycle.com/about-us/.