Green Chemistry Principle #10: Design for Degradation

By Shira Joudan, Chair of the Education Subcommittee for the GCI

10. Design for degradation: Chemical products should be designed so that at the end of their function they break down into innocuous degradation products and do not persist in the environment.

In video #10, Matt and I discuss designing chemicals that break down once their desired function is completed. Essentially, we want chemicals to degrade to molecules that are not harmful to humans, animals or the environment.

A lot of the chemicals we use in our day-to-day lives need to be stable to perform their function. For example, if your coffee mug dissolved when you poured your coffee into it, it wouldn’t be very helpful! Similarly, if lubricants degraded under high temperature and pressure, they may not work well in the engines of our cars or planes.

Once chemicals are done providing their main function, they might end up in a landfill or wastewater treatment plant where they can enter the waters, soil and air of our environment, or be taken up by animals or humans. The biggest challenge is making chemicals that are stable during usage, but don’t persist in the environment – or in other words, chemicals that can be degraded. Another important thing – we want the breakdown products to also be non-toxic and not persistent! It’s important to remember that there are different reasons a chemical can break down. It can be due to reactions with light (photodegradation), water (hydrolysis) or biological species, often with enzymes (biodegradation).

A common example that we hear about is biodegradation, especially with the well-known “biodegradable soaps.” We can use this as a good example about how we can design soaps, or detergents, to break down more easily in the environment.

Sodium dodecylbenzenesulfonate

Figure 1 Sodium dodecylbenzenesulfonate, an example of a linear alkylbenzene sulfonate (LAS) which is biodegradable.

Sodium dodecylbenzenesulfonate (Figure 1) is a common detergent, and is often referred to as LAS, for linear alkylbenzene sulfonates. Looking at its structure, you can see that it has a linear alkyl chain with a benzylsulfonate attached to it. It is useful as a detergent because it has a polar headgroup (sulfonate) and a non-polar alkyl group, making it a surfactant.

LAS is used in many things, especially laundry detergent. It degrades quickly in the environment under aerobic conditions, or when oxygen is present, because microbes are able to use to the linear alkyl chain as energy, via a process called β-oxidation, a process which breaks down the carbon chain. Once the long chain is degraded, the rest of the molecule can be degraded as well.

Branched alkylbenzene sulfonate.

Figure 2 A branched alkylbenezene sulfonate (does not biodegrade).

If you compare LAS to a branched version (Figure 2), you can immediately see that the alkyl chain looks very different. This molecule was also used as a detergent just like the linear version, but because of the location of the branches, microbes cannot perform β-oxidation since there are no good sites for that reaction to be initiated. Therefore, these branched detergents have been phased out in most developed countries because they are too persistent – they do not biodegrade.

The main way these molecules are degraded is through microbes, when oxygen is present. So if these soaps end up directly in water, like straight into a lake, they will not be broken down very quickly (even the linear version!). This is because there are fewer microbes in water as compared to in soil. Interestingly, the branched version is 4 times less toxic than the linear version, but can cause more damage because of its persistence. This is one of the reasons that it is very important to consider persistence, or a molecule’s resistance against degradation, and not only its toxicity.

You can see how designing chemicals to break down can be very challenging, but many researchers around the world are working on this right now. Some examples are biodegradable polymers that are used in plastics, like compostable cutlery.

Principle 10 is currently one of the largest challenges in green chemistry. If scientist designing new chemicals understand more about the mechanisms that can degrade them, we may be able to make chemicals that are reliable and stable during their intended use, but break down in the environment!

Celebrating the 5-Year Anniversary of the GCI

Celebrating the 5-Year Anniversary of the GCI

By Alex Waked, Co-Chair for the GCI

The Green Chemistry Initiative (GCI) at the University of Toronto was founded back in 2012 – it’s crazy to think that we’ve already reached the 5-year milestone. Before you know it, it’ll be 10 years, then perhaps even 20 years! But before we talk about the future, it’s always a good idea to take a step back and reflect on how we’ve gotten here in the first place. This organization wouldn’t even exist had it not been for the vision of co-founders Laura Hoch and Melanie Mastronardi, with help from many graduate students keen on educating themselves and their peers about sustainable practices. With the help of all the other dedicated GCI members over the years, they helped the GCI grow to the point at which we’re now standing. Being the 5-year anniversary of the GCI, I reached out to all the previous co-chairs and asked them to reflect on their time spent here.


GCI group photo from 2013

Laura Hoch (Co-Chair from 2012-2015):

I’m so excited to help celebrate the GCI’s 5-year anniversary by sharing some reflections and favorite memories from my time with the group. When I look at all the GCI has done over the past 5 years, I am so happy to see how much impact we’ve had. Within our own department, all the events and initiatives – trivia, seminars, workshops, the waste awareness campaign, and many more – have really raised awareness about green chemistry and made it more tangible. Through our work, we have also helped to inspire other students in Canada and around the world to get active, start their own student groups, and promote green chemistry in their own communities.

It’s really hard for me to pick a favorite event or project that I am most proud of – in my extremely biased opinion, we’ve done way too many awesome things! – but for me one of the moments when it really hit home how much of an impact we were having was at a networking session at the ACS Green Chemistry & Engineering Conference in Washington D.C. Waiting in the food line, I randomly ended up talking to a researcher at DuPont. When I mentioned that I was from U of T, he said “Oh! Are you one of those intrepid students from Toronto?!” and proceeded to describe in detail many of our activities and initiatives. It blew my mind that here was a complete stranger from Delaware, who wasn’t even an academic, who had heard of us and thought what we were doing was great.

I can honestly say that helping to start the GCI was by far the BEST thing I did in grad school. I’ve learned so much and have met so many amazing people through our work. I am so proud of what the GCI has accomplished and I really look forward to seeing what the GCI will do in the years to come!

Melanie Mastronardi (Co-Chair from 2012-2014):

It seems like just yesterday that we started the GCI, I can’t believe it’s been 5 years already! Thinking back to where we started (just a handful of grad students who wanted to learn how to conduct our research more sustainably), I’m so proud of all the GCI has been able to accomplish. From weekly trivia challenges to department seminars to hosting students and speakers from all over at our annual symposium, the GCI has created so many opportunities for students and researchers to learn about green chemistry and how to implement it. It’s also absolutely amazing to hear stories of how we inspired students at other universities to start similar organizations! One of my personal favourite projects was launching the 12 Principles of Green Chemistry video campaign. We’ve come a long way from the first one we filmed in Jes’ kitchen and last time I checked we are only 3 away from completing the full set!

Laura Reyes (Co-Chair from 2014-2016):

I am so grateful and proud to have been a founding member and co-chair for the GCI, and continue to be impressed by everything that the group does. It feels surreal to look back on everything that we have accomplished in only 5 years. The GCI started from the curiosity of a few grad students wanting to know how green chemistry could be applied to our own research, and now the group is well-known and respected throughout the green chemistry community as an example of a student-driven education effort. In that time, the GCI has managed to change the conversation around green chemistry in the UofT chemistry department. Subtle changes have compounded into a larger cultural shift, including anything from curriculum development for undergrad courses and labs (and signing Beyond Benign’s Green Chemistry Commitment!), to faculty members self-identifying as using green chemistry in their work. There is still much progress to be made, of course, but looking back on the accomplishments of the GCI and the professional experience that we all gained in being a part of this, it is hard to not feel proud of every project and event that we organized, starting with our very first seminar on the basics of green chemistry to recently teaching that seminar ourselves at the 100th CSC conference!

GCI group photo 2017

GCI group photo from 2017

Erika Daley (Co-Chair from 2015-2016):

Congratulations to all previous and current members of the Green Chemistry Initiative on its 5th anniversary! I was incredibly proud of all the accomplishments and activities that took place during my time as co-chair, and continue to be delighted by the success of the group. I think the value is especially put into perspective in my career when researchers, faculty, students, and industry employees know of or recognize the GCI and the impact it has had all over North America. While it is impossible for me to pick one particular initiative to highlight here, I think the collective outreach, education, data collection, and subsequent actions of the entire GCI team – from the departmental waste awareness campaign, to the community outreach events, to the undergraduate curriculum development – are all so important and speak volumes to what a group of dedicated student volunteers can accomplish.

Ian Mallov (Co-Chair from 2016-2017):

The 5-year anniversary of the GCI is an opportunity to reflect on our mission and goals. What did we want to accomplish, and what have we accomplished? Personally, I’m most proud of the fact that we have successfully ingrained green chemistry education into the fabric of our department through establishing regular events like symposia, seminars, and trivia, and that we helped encourage the department to sign the Green Chemistry Commitment. Green chemistry education should be fundamental to chemical education – it is our job as chemists to understand matter at the molecular and nano levels. I view the primary mission of green chemistry as a mission to impart a sense of responsibility to chemists to manage matter safely. I would hope the GCI has brought more chemists at U of T and beyond to consider this responsibility, and I’m really encouraged by the bright, dedicated people who continue to lead the GCI forward.