By: Carlos Navarro

What’s up! My name is Carlos Navarro and I am a rising 5th year Ph.D. student studying chemistry at USC. I am a member of Travis Williams’ lab where I work on developing an effective recycling method for carbon fiber reinforced polymer composites, or CFRPs for short.

CFRPs are a mouthful to say and sound uncommon, but there’s a really good chance you’ve interacted with one recently! We are using them to build all kinds of products and goods, from airplanes to bicycles, because they have a higher strength-to-weight ratio than steel. This is great news for airplanes because we can improve fuel efficiency by using CFRPs to make them lighter, and its great news for consumer goods like golf clubs and bicycles because they are sleek, perform great, and last a long time.

This, however, is bad news for the environment, because there is no effective recycling method for CFRPs when we’re done using them! The best methods being developed right now involve shredding the CFRP into chips and heating them in giant furnaces at 700 °C, which recovers only a fraction of its value for re-use. We need to do better, which is why I’ve been working on this project for the past 5 years!

This is the last thing our carbon fiber composite samples see before I recycle them.

“Why are CFRPs so difficult to recycle?”, you may be asking yourself. Firstly, great question! Second: it all comes down to the polymer which holds the composite together. CFRPs are manufactured by layering sheets of carbon fiber weaves and smothering the stack in an epoxy polymer – just like the ones sold at hardware stores as a pack of two bottles. These polymers are extremely durable and non-reactive, which is great when you’re in an airplane made from CFRPs, but not-so-great when you want to recycle the airplane afterwards. This is a problem that we’re going to be facing in the near future!

Newer generation aircraft like the Boeing 787 are 50% by weight CFRPs! Thankfully airplanes have about 30 year service lives, but we will need to deal with this waste eventually…

Since the root of the CFRP recycling problem is chemistry, we’ve decided to use chemistry to try to solve it! My research focuses on finding mild reaction conditions to undo the chemical bonds which form the polymer. Our best set of recycling conditions so far relies on using oxygen gas and metal catalysts to break the polymer bonds that are formed when it is cured, but it requires a lot of pressure. This makes the recycling reaction difficult to scale up if we want to try to make it commercially viable.

A side-by-side photo of a cured CFRP sample (left), and a recycled carbon fiber weave (right) recovered from these composites using our process. Those fiber weaves are incredibly valuable – so valuable that I have started a business for reselling them! Fingers crossed it goes well!!!

That’s why I spent the summer studying ways to either replace oxygen gas or find a way to reduce the amount of pressure. One particularly exciting project we did this summer involved making 1 cm3 polymer cubes and injecting them with a special compound which reacts with oxygen gas as it moves into the cube. We could track, in real-time, how quickly a gas was moving through a solid!! This is valuable information as I try to optimize and make this reaction as efficient and effective as possible (I wish I could share more details and photos on that, but I’ll update this blog post once we have published the paper and I’ll break it all down!).

A blue LED is connected by a conductive epoxy to a nut on the top of the reactor. We can connect the leads to an external power supply and provide light to the inside of the vessel!

This summer, I also got to use a special photo-reactor to try to recycle composites photochemically – meaning that light is also a reagent and helps destroy the polymer! With this reactor, I can illuminate the sealed interior and apply a gas pressure so I can test how much I can reduce the applied pressure while still recycling the CFRP.

I want to give a big thank you to the Wrigley Institute for selecting me for the Sonosky Sustainability Fellowship this summer – I can’t wait to make you all proud!!

By: Kyla Kelly

Hi everyone! My name is Kyla Kelly, and I am a 4th year Ph.D. candidate in the University of Southern California’s Marine Biology and Biological Oceanography program. As a member of Dr. David Hutchins’ lab, I study marine harmful algal blooms in the face of climate change. These toxic phytoplankton (commonly known as “red” or “brown tides”) bloom annually off the west coast of the United States, threatening human health, marine ecosystems, and local economies. Learning more about them though research could provide HAB monitoring and coastal management agencies with a greater understanding of what may be causing these toxic blooms to occur, and how they may be exacerbated by climate change.

Me taking care of my phytoplankton in the lab (left) and me enjoying the great outdoors (when not in the lab; right).

As a recipient of the Wrigley Institute’s Norma and Jerol Sonosky Summer Sustainability Fellowship , I spent my summer studying how a red tide-causing species (Alexandrium sp.) may be affected by two climate change variables: warming and nutrient limitation. Climate change is causing surface ocean temperatures to rise, so the phytoplankton living there must endure these warmer, potentially stressful conditions. This may change the way that Alexandrium sp. grows and produces saxitoxin – a neurotoxin that, when ingested, can be harmful to human health.

Nutrient limitation may also alter the way that Alexandrium sp. “behaves”. Warming can cause the ocean to become more stratified (i.e., the nutrient-rich bottom waters have trouble mixing with the nutrient-depleted surface waters). Nutrients such as phosphate and nitrate are essential to phytoplankton growth, yet this stratification could reduce the availability or supply of these nutrients. Furthermore, warming can interact with nutrient limitation by changing how efficiently phytoplankton can absorb these nutrients. This could have implications for toxic bloom formation by Alexandrium sp..

Alexandrium sp. cells under the microscope. Note the scale bar – these guys are pretty tiny! Image from https://green2.kingcounty.gov/marine/Photo/Individual/2/406?photoId=1048

We are performing an experiment to figure out how Alexandrium sp. may be impacted by the simultaneous warming and nutrient limitation we expect in a future ocean altered by climate change. We are using a thermal block to create a gradient of temperatures ranging from 12 to 26°C – with 12°C representing wintertime ocean temperatures, 22°C reflecting temperatures we see in the summer, and 26°C representing a future, warmer ocean. Each column in the thermal block is a different temperature, with cooler treatments on the left, and warmer treatments to the right. Within each column, we are growing Alexandrium sp. in 9 culturing flasks: three have all the nutrients they need to grow normally (this makes them happy), three have less phosphate available and are considered “phosphate limited”, and three have reduced concentrations of nitrate, and are therefore “nitrate limited”.

Our experimental setup in the thermal block. The coldest temperature treatments are all the way to the left in column one. Each successive column increases approximately 1-1.5°C, moving to the right.

This experiment is still in progress. The phytoplankton are currently acclimating (or getting used to) to experimental conditions. Once acclimation has been achieved, we expect to see differences in growth rates and toxin production for each temperature and nutrient treatment. We predict that warmer, phosphate limited treatments will grow slower, but produce more toxins (compared to colder, nitrate limited treatments).

These data will help us learn how nitrate and phosphate play different roles in growth and toxin production, and how temperature may impact the way in which Alexandrium sp. uses these nutrients. I am excited to continue working on this research project, and thankful for being awarded the Sonosky Fellowship in support of my work!