Green Chemistry Principle #7: Use of Renewable Feedstocks

By Trevor Janes, Member-at-Large for the GCI

7. A raw material or feedstock should be renewable rather than depleting whenever technically and economically practicable.

In Video #7, Yuchan and Ian help us understand what a raw material or feedstock is, and why we need to choose feedstocks which are renewable.

They use CO2 as an example of a feedstock which plants convert into sugar via photosynthesis. We humans use this sugar as our own feedstock for many different delicious things, including cookies! Yuchan and Ian explain that for a feedstock to be renewable, it must be able to be replenished on a human timescale, whereas depleting feedstocks take much longer to be replenished, and are being used up at a faster rate by human activity.

Many common feedstocks are depleting, such as petroleum and natural gas. The petrochemical industry uses petroleum and natural gas as feedstocks to make intermediates, which are later converted to final products that people use, such as plastics, paints, pharmaceuticals, and many others.

An example of a renewable feedstock is biomass, which refers to any material derived from living organisms, usually plants. In contrast to depleting feedstocks like petroleum, we can much more easily grow new plants once we use them up, and maintain a continuous supply. If we can use bio-based chemicals to do the same tasks that we currently accomplish using petrochemicals, we move closer to the goal of having a steady, reliable supply of resources for the future.

Existing chemical technology has developed based on using readily available petroleum as feedstock to make a majority of chemicals and end products. However, the chemical technology that enables conversion from biomass into bio-based chemicals into final products people use is not yet as well developed.1 Chemical scientists with various specializations are currently involved in improving our ability to use biomass.2, 3

So, how can we implement the principle of renewable feedstocks on a day-to-day basis? Yuchan and Ian illustrate principle 7 through their choice of solvent. As we explore in the video for principle #5, we choose a solvent for a particular purpose based on properties such as boiling point, polarity, and overall impact on health and the environment. One more aspect to consider is that we can choose to use a solvent based on is its renewability. Tetrahydrofuran (THF) is a useful ether solvent, but it is synthesized industrially from petrochemicals (see below for synthesis), so it isn’t renewable. A close relative of THF is 2-methyl THF. Its structure and properties are very similar to those of THF, but the difference is that 2-methyl THF can be synthesized from bio-based chemicals which are made from renewable feedstocks. So when we substitute 2-methyl THF in for THF, we are putting principle 7 into action.

Synthesis of THF4 vs. synthesis of 2-methyl THF5

screen-shot-2016-10-25-at-10-35-31-pm

The synthesis of THF.

An early step in the industrial production of THF involves reaction of formaldehyde with acetylene to make 2-butyne-1,4-diol. This intermediate is hydrogenated and cyclised in two more steps to yield THF. The acetylene input is derived from fossil fuels, which again are non-renewable.

screen-shot-2016-10-25-at-10-35-48-pm

The synthesis of 2-methyl THF.

An alternative to THF is 2-methyltetrahydrofuran, which has a very similar structure to THF.  It can be synthesized starting from biomass; after conversion to C5 and C6 sugars and subsequent acid-catalyzed steps, the intermediate levulinic acid can be hydrogenated to yield 2-methyl THF.

References:

  1. “Renewable Feedstocks for the Production of Chemicals” Bozell, J. J. ACS Fuels Preprints 1999, 44 (2), 204-209.
  2. “Conversion of Biomass into Chemicals over Metal Catalysts” Besson, M.; Gallezot, P.; Pinel, C. Chem. Rev. 2014, 114 (3), 1827-1870.
  3. “Transformation of Biomass into Commodity Chemicals Using Enzymes or Cells” Straathof, A. J. J. Chem. Rev., 2014, 114 (3), 1871-1908.
  4. “Tetrahydrofuran” Müller, H. in Ullmann’s Encyclopedia of Industrial Chemistry 2002, 36, 47-54.Wiley-VCH, Weinheim. doi:10.1002/14356007.a26_221
  5. “Synthesis of 2-Methyl Tetrahydrofuran from Various Lignocellulosic Feedstocks: Sustainability Assessment via LCA” Khoo, H. H.; Wong, L. L.; Tan, J.; Isoni, V.; Sharratt, P. Resour. Conserv. Recy. 2015, 95, 174.
Green Polymer Chemistry: Approaches, Challenges, Opportunity

Green Polymer Chemistry: Approaches, Challenges, Opportunity

By Hyungjun Cho, Member-at-large for the GCI

I was recently inspired by an episode of podcast by NPR’s Planet Money called Oil #4: How Oil Got Into Everything. It told the story of Leo Baekeland’s invention of Bakelite, which is the plastic that made many commodities affordable for the masses.

Plastic is made of polymers, and many of the common items we use are made from one or more of these polymers. Examples of these polymers are polystyrene, polymethylmethacrylate, and polyethylene and some examples of common items that contain these polymers are Styrofoam™, Plexiglas®, and plastic bags, respectively. Polymers are synthesized by forming bonds between many molecules of same structure, called monomers.

Conventionally, these monomers are produced from chemicals derived from oil, which is a non-renewable feedstock. Environmentally conscious scientists have been trying to make polymers in a more eco-friendly way. The biggest challenge lies in how we obtain monomers from renewable sources.

There are two main approaches to this challenge. The first approach is to produce currently used monomers, such as styrene, from a renewable source. A literature review by Hernandez et al.1 called this approach bioreplacement. The biggest progress in this

oct-1

Figure 1. Engineered metabolic pathway to produce styrene from glucose. (1)

approach has been made by engineering the metabolic pathways of bacteria cultures. McKenna et al. 3 have been able to feed glucose to engineered E. coli to produce styrene and release it in the culture medium they are incubating in. The E. coli flask cultures were able to produce styrene to reach concentrations of up to 260 mg/L1,3. Figure 1 shows the metabolic pathway from glucose to styrene.

While this method of producing monomers is promising, there are road blocks that are hindering progress. The biggest issue is toxicity of styrene to the E. coli, which limits the maximum concentration of styrene in the bacterial culture (E. coli can only tolerate up to 300 mg/L styrene1,3). Other challenges that exist with using bacteria include long incubation times, obtaining poor yield of desired product relative to amount of glucose added, and scale up. Looking down the road, these kinds of limitations may prevent this method from being economically and practically viable.

The second approach is called bioadvantage. Polymer chemists take chemicals that are already being produced from renewable feedstock, synthesize polymers, and use said polymers to produce polymer products in hopes of replacing already existing polymer materials. There are many molecules that are being studied for this purpose such as cellulose, starch, anethole, methylene-butyrolactone, and myrcene.

oct-2

Figure 2. Conventional monomers (styrene, methylmethacrylate, ethylene) and their potentially renewable counterparts. Renewable counterpart monomers tend to be structural analogues of conventional monomers.

During the podcast by Planet Money, research by the Hillmyer group from University of Minnesota was featured. They aim to synthesize eco-friendly polymer using monomers from renewable feedstock (the bioadvantage method). After many failures to produce viable polymer from corn, coconut, orange peels, etc., they were able to develop a polymer synthesized from a menthol derivative obtained from peppermint2.

A critical challenge to bioadvantage polymers is the need for years of study and passing a battery of regulatory tests before they are adopted. The petroleum based polymers that are being used today already have been researched for decades, which allows them to be used easily by industry. By extension, bioadvantage polymers will need to match or exceed their performance in terms of strength, durability, flexibility, and other properties we require from our plastic. Even when industry is willing to allocate resources to adopt eco-friendly polymers, sometimes it’s the consumers that prove to be even less accommodating. We observed this with the biodegradable bag fiasco by Sun Chips.

It should be mentioned that both bioreplacement and bioadvantage polymers are not necessarily biodegradable. Therefore, we should not call them green polymers.

I will conclude with this: I see the impact that plastic has on our daily lives and I see demand for polymers. Being able to make eco-friendly polymers economically will change the world around you, literally. As Planet Money teaches, the world works in a supply-demand swing. When the kinks in the supply side of eco-friendly polymers are fixed, demand for them will present itself. How soon eco-friendly plastics will develop will depend on us. As green chemists, we should see that the biggest impact we might have in the future, will be making eco-friendly polymers.

References

(1)   Hernández, N.; Williams, R. C.; Cochran, E. W. Org. Biomol. Chem., 2014,12, 2834-2849

(2)   Hillmyer, M. A.; Tolman, W. B. Acc. Chem. Res., 201447 (8), pp 2390–2396

(3)   Mckenna, R.; Nielsen, D. R. Metab. Eng. 2011, 13 (5), 544–554.

UofT Demonstrates its Commitment to Sustainable Chemistry

“We’re very pleased and proud to announce that the Chemistry Department has recently joined the Green Chemistry Commitment (GCC)!” – Dr. Andy Dicks, University of Toronto, Associate Professor

gci-group-photo-sept27-2016

GCI Members Fall 2016

The University of Toronto has recently signed the GCC making us the first school outside of the United States to sign onto this impactful commitment, which now contains 33 colleges and universities. The GCC is overseen by Beyond Benign, a United States not-for-profit organization created by Dr. Amy Cannon and Dr. John Warner, a founder of the principles of green chemistry. Within the GCC, academic institutions collaborate to share resources and know-how in order to positively impact how the next generation of scientists are educated about sustainability issues. Participating departments commit to green chemistry instruction as a core teaching mandate. The aim is to provide undergraduates and graduates with the required understanding to make green chemistry become standard practice in laboratories around the world. This, in turn, ensures that when graduates of the university enter the workforce, they are armed with the knowledge of how to make molecules and processes more sustainable and less toxic by adhering to the Twelve Principles of Green Chemistry.

The GCC unites the green chemistry community around shared goals and a common vision to grow departmental resources to allow a facile integration of green chemistry into the undergraduate laboratories as well as to improve connections with industry which creates job opportunities for sustainability-minded graduates. Their website offers many resources for those interested in reading actual case studies and laboratory exercises, so please click here to visit their website and be informed!

Our chemistry department has already improved the green chemistry content in our undergraduate laboratories by updating the first year courses and upper year synthetic chemistry courses to include various graded questions about the Twelve Principles as well as ensuring the undergraduates are thinking about how they could make their current lab protocols more sustainable. Additionally, students can choose to study the fate of chemicals in our environmental chemistry courses offered. Of course there’s always room to improve, so the Green Chemistry Initiative (GCI), in collaboration with Dr. Andy Dicks, is working on evaluating the undergraduate chemistry curriculum’s current focus on sustainable chemistry and toxicology, in hopes to further improve our undergraduate’s learning experience. The GCI also provides many educational opportunities to department members such as our Seminar Series as well as many outreach opportunities, making our group a driving force in the integration of green chemistry principles to the department. Lastly, the University of Toronto chemistry courses reach thousands of students a year, and by being the first Canadian university to sign this commitment, we are working towards a greener future in Canada!

Thank you for celebrating this very momentous achievement with us!
Karl Demmans, Ian Mallov, Shira Joudan, and Laura Reyes

Just Shut It!

By James LaFortune and Shawn Postle, Members-at-large for the GCI

The Green Chemistry Initiative (GCI) and the University of Toronto constantly strive to reduce the environmental impact inherent to research in the Chemistry Department.  A major contributor to the department’s carbon footprint is its fume hoods, which are required to safely carry out experimentation with volatile solvents or reagents.  They provide a partially enclosed working space that draws air from the laboratory into the hood, thereby reducing the researcher’s exposure to chemicals. However, this requires replacing the removed air with acclimatized outside air, a process which consumes large amounts of energy in heating or cooling the air.

Fume hoods are designed with a height-adjustable glass pane (sash) that allows the researcher to work while keeping the space as enclosed as possible. There are two main types of fume hoods used in chemistry labs: constant air volume (CAV) and variable air volume (VAV).  With CAV, the air flow remains constant regardless of sash height, while VAV systems are designed to moderate air flow based on the sash height.  Each fume hood requires roughly as much energy as three American households when in use.  However, roughly 50% of this energy can be conserved in VAV systems if the sash is kept shut.  Given that the Chemistry Department has 123 VAV fume hoods, ensuring that VAV sash heights are minimized during idle periods is an effective strategy to reduce unnecessary energy consumption.1

james_shawn-blog

The GCI’s Just Shut It! Campaign, renewed this past summer for its third season since 2008, encourages graduate students to close VAV fume hood sashes during idle times and to minimize sash height when working in the hood.  Fume hoods are checked weekly by GCI volunteers to ensure compliance and users of fume hoods found to be in compliance are entered into monthly prize draws.  The past two Just Shut It! Campaigns (read more about the original campaign) were very successful, where compliance rates increased from 3% to 61% during the campaign. Since its reinvigoration over the summer, we have recorded similar compliance levels as previous campaigns.

What’s more, the Chemistry Department currently only uses VAV fume hoods in its Davenport wing.  However, it is exploring air systems renovations, including replacing CAV with VAV fume hoods in much of the Lash Miller wing.  These additional VAV fume hoods will further decrease our environmental impact.

This time around, we are looking to keep the Just Shut It! Campaign going permanently.  Gracious thanks to the Department of Chemistry for funding this campaign, especially Chief Administrative Officer Mike Dymarski.

  1. E. Feder, J. Robinson and S. Wakefield, International Journal of Sustainability in Higher Education, 2012, 13, 338-353.

Green Chemistry: From the Bench Top to Industry, A Chemical Engineer’s Perspective

By Cynthia Cheung, Member-at-Large for the GCI

As a chemist, do you ever think about how to scale up your chemical reactions, or your chemical processes? For most of us, the answer is no. However, this idea of industrial scale is something that is constantly addressed in the Chemical Engineering and Applied Chemistry department. Consequently, the 12 Principles of Green Chemistry become fundamental to scale up a reaction from the bench top in a research lab to mass production in a chemical plant (Figure 1).

Cynthia_blog post figure 1

Figure 1. Example of a chemical plant design [1]

For me, the biggest difference I have found moving from the Chemistry department to the Chemical Engineering department is that the principles of Green Chemistry are not concepts that Chemical Engineers often have to think about or address, because these principles are integrated and engrained into their work as objectives and limitations. A process can be thrown out simply because it uses columns for purification (which cannot be done on a large scale, because you would need truckloads of solvent) or because one of the reagents is toxic.

As a chemist, we do what works and worry about alternatives after we have established what we targeted. So pause and think about it for a second: can you continue what you’re doing and upscale it from milligrams to tonnes? Even theoretically speaking, if you could produce that much product, would that process make sense? For example, would that Stille coupling reaction be safe when you’re using tonnes of tin2, or could you afford to be using or making catalysts when you need tens of kilograms of it? So how to do you go about engineering your process so that it would be suitable for industry? Rather, how do the engineers do it?! Well, broadly speaking (and from asking around) a few of the main considerations that seem to be in common are:

Cost Analysis

How much are all of the reagents and solvents going to cost, and where are there substitutes for cheaper alternatives?

Rate of Reaction

How long is this reaction going to take? Because time is money.

Waste

How much waste is produced, what type of waste and is it recyclable? Also to keep in mind is if the waste is hazardous, then what alternatives can be used from the beginning to avoid any hazardous waste generation? In addition, if there’s pollution, then that also has to be reduced or eliminated altogether.

Work up

This consideration is often tricky, as most organic labs usually use techniques that are not scalable (I’m looking at those purification columns). In addition to that, side products and by-products are also something that often can give engineers a headache. Atom economy is very important for industry, as it lessens the amount of waste produced, and also aids in producing a good product yield.

Energy Consumption

How much energy is required for a reactor and for a chemical plant to run is also part of the cost analysis for a process. It would definitely be preferential to be using less energy (so lower temperature reaction conditions and reactions that generate no heat). Essentially, if all reactions could be at room temperature, that would be perfect.

So with these considerations in mind, could you re-engineer your synthesis?

 

References:

[1] http://en.citizendium.org/wiki/File:FCC.png

[2] Stille, J. Palladium Catalyzed Coupling Of Organotin Reagents With Organic Electrophiles. Pure and Applied Chemistry 1985, 57.

Leading by Example in the Lab

Leading by Example in the Lab

By Ian Mallov, Co-Chair for the GCI

Ask a scientist what their greatest satisfaction is from research.  Most will probably tell you something along the lines of “the pursuit and discovery of new knowledge.”

Some will mention the parallel satisfaction of originating inventions or techniques that are broadly applicable, and seeing that work applied for the benefit of society.

Much of the challenge of moving towards a truly sustainable culture is in applying what we’ve already shown to be effective on small scales.

Two years ago, the Green Chemistry Initiative’s 2014 Workshop team developed ten recommendations entitled “Simple Techniques to Make Everyday Lab Work Greener.”  Led by co-founder Laura Hoch, with important contributions from Cookie Cho and Dr. Andy Dicks, we publicized these during the workshop.  So what has happened to these recommendations since?  They’ve been developed – are researchers in our department incorporating them into their work habits?  Are we ourselves applying what we already know to be effective?

I was pleasantly surprised to find out that a number of our researchers were in fact using these greener lab techniques.  In an effort to make their use even more widespread, I’d like to highlight some examples of researchers in our department who are leading by example.

Further, next week our “Simple Techniques to Make Everyday Lab Work Greener” poster will be posted around the department!


Ian_July blog 1

 

Scientist: Karlee Bamford, Stephan lab

Technique: Recycling solvents from rotovap to use for cleaning vials and glassware

Why it’s greener: Saves solvent, reduces waste generated, and reduces energy used in production and disposal of additional solvent

Issues to Consider: Use in synthesis and purification often requires solvents to be more pure than those collected from rotovap


Ian_July blog 2Scientist: Aleksandra Holownia, Yudin lab

Technique: Setting GC to stand-by mode when not in use

Why it’s greener: The GC uses much less helium gas (a rapidly diminishing resource) and reduces the temperature of the oven, saving energy

Issues to Consider: Does take a few minutes to start up again


Ian_July blog 3Scientist: Karl Demmans, Morris lab

Technique: Using 2-methyl THF as a reaction solvent instead of THF

Why it’s greener: 2-methyl THF is derived from the aldehyde furfural, sourced from renewable crops.  THF, on the other hand, is derived from fossil fuels.  While crop-sourcing does not automatically make it “greener,” consensus in the case 2-methyl THF is that it is indeed less energy- and resource-intensive to produce than THF.

Issues to Consider: Unlike THF, it is immiscible with water.  Slightly less polar than THF


Ian_July blog 4Scientist: James LaFortune, Stephan lab

Technique: Isopropanol/dry ice instead of acetone/dry ice for cold baths

Why it’s greener: An Isopropanol/dry ice bath maintains a temperature of -77 oC, almost exactly the same as acetone/dry ice’s -78 oC.   However, isopropanol is much less volatile (bp: 83 oC) than acetone (bp: 56 oC); practically, this allows for the recovery and reuse of the isopropanol after several hours or overnight, while acetone evaporates.

                                                                          Issues to Consider: Must actually recover and reuse the isopropanol!


Ian_July blog 5

Scientist: Samantha Smith, Morris lab

Technique: Closing the fume hood sash when not in use.

Why it’s greener: Modern, variable-flow fume hoods – used in the Davenport wing of our building – regulate the strength of their vacuum for safety based on how far open the fume hood is.  When wide open, the fume hood uses much more energy than when closed (see Just Shut It campaign!)

Issues to Consider: Is your fume hood variable-flow?

 


Ian_July blog 6Scientist: Brian de la Franier, Thompson lab

Technique: Using a closed-loop cooling system for refluxes and distillations.

Why it’s greener: Uses much less water.  While some of our undergraduate labs have built-in closed-loop cooling systems, Brian simply got a small fish tank pump from a pet store and uses a Styrofoam box with ice to keep his water cold – a very easy DIY solution!

Issues to Consider: Does water saved compensate for the extra energy for the ice/pump?  Consider the energy used to purify and deliver the extra water and we can safely say yes.


Ian_July blog 7

Scientist: Alex Waked, Stephan lab

Technique: Reusing rubber septa used to seal Schlenk flasks

Why it’s greener: Saves materials and money

Issues to Consider: There is a limit to their reusability.  At some point, if a septum has been perforated by too many needle holes it is no longer an effective seal.  Must also ensure septa are kept clean.


Ian_July blog 8

Scientist: Molly Sung, Morris lab

Technique: Reusing gas chromatography vial caps by replacing their septa

Why it’s greener: Saves materials and money

Issues to Consider: Somewhat time-consuming to remove and replace rubber septa for each cap

 


Ian_July blog last

Easy Peasy Lemon Squeezy – An Eco-Friendly Process for Pectin and Essential Oil Extraction From Lemon Peels

By Alex Waked, Member-at-Large for the GCI

Industrial scale chemistry is not typically given much thought by most chemists in academia. But if the end goal is to produce our products for eventual commercial use, then why not design our syntheses and processes at the beginning to ensure that the scaling up will be smooth?

Fidalgo et. al. recently published a paper that caught my eye, in which they describe a scalable eco-friendly process for the simultaneous extraction of pectin and the essential oil d-limonene.1 Pectin is a heteropolysaccharide that has found use in a wide variety of products. It can be used as a thickening agent in jams and shampoos,2 in the medicinal field in wound-healing preparations, and has been shown to reduce blood cholesterol levels.3 In 2013, the global market for pectin reached $850 million.4 In a few words, it’s a valued, versatile product.

Pectin is contained in plant cell walls, and is extracted from citrus peel (such as lemons and oranges) traditionally by a water extraction method. This method involves heating the citrus peel for several hours under acidic conditions, filtering off the solid residue, concentrating the filtrate, and finally precipitating the pectin by addition of alcohol. A couple drawbacks include the large amount of acid waste and the excessive heating of the peel, which degrades the pectin as well as being energy intensive.

Alex_blog post figure 1

Figure 1. Microwave hydrodiffusion and gravity apparatus [5]

In this paper, the authors used two innovative methods to obtain pectin from lemon peels (the pectin obtained from both methods have slightly different properties which I won’t go into, but if you’re curious I encourage you to take a look at the paper!). The first method includes adding water to lemon peels, doing a microwave hydrodistillation (which is simply a distillation using microwave heating), separating the essential oil from the residual water, and finally freeze-drying the water to obtain pure pectin. The second method involves a technique called microwave hydrodiffusion and gravity,5 where the lemon peels and water are heated using a microwave source and the residual liquid that is expelled by the heating is passed through a filter and condenser to be collected (Figure 1). The collected aqueous solution is then freeze-dried to obtain pure pectin.

The first method was employed to test whether this process would be compatible with kilograms of material. It turns out that 20 kg of waste lemon peels produces 3 kg of pectin and 10 mL of essential oil, where 36 L of water was used (Figure 2). To put these numbers in perspective, common yields for pectin from the more conventional extraction methods are only roughly 3% of the peel weight – so 20 kg of lemon peels would produce 0.6 kg of pectin.

fig2

Figure 2. The semi-industrial scale extraction process presented in the paper [1]

So let’s take a look at some of the positive takeaways from this paper: 1) Significantly better yields of pectin were obtained compared to the current conventional processes; 2) Microwave heating (which is the only energy source in the processes) requires less time than normal heating, meaning less degradation of pectin and lower energy usage; 3) Water was the only solvent used, and; 4) This was the first reported simultaneous extraction of pectin and essential oil by an environmentally clean process.

References:

(1) Fidalgo, A.; Ciriminna, R.; Carnaroglio, D.; Tamburino, A.; Cravotto, G.; Grillo, G.; Ilharco, L. M.; Pagliaro, M. ACS Sustainable Chem. Eng. 20164, 2243–2251.

(2) Willats, W. G. T; Knox, J. P.; Mikkelsen, J. D. Trends Food Sci. Technol. 2006, 17, 97−104.

(3) Wicker, L.; Kim, Y.; Kim, M.-J.; Thirkield, B.; Lin, Z.; Jung, J. Food Hydrocolloids 2014, 42, 251−259.

(4) Bomgardner, M. M. Chem. Eng. News 2013, 91, 20.

(5) Viana, M. A.; Fernandez, X.; Visinoni, F.; Chemat, F. J. Chromatogr. A 2008, 1190, 14–17.