It wasn’t until halfway through my research that I realised the sheer undertaking of this research. I spent many hours making quite a detailed Gantt chart of how the 10 or months of research would look like. Exact dates for collection of samples and experiments, the dates of cleaning the reactor and performing analysis. Was I in for a surprise… But also, a learning experience.
Stuff didn’t go as planned so I had to adapt. I already met a stumbling block at the beginning when collecting and cleaning the plastic waste. Utrecht University collects plastic waste in PMD bags, these are plastics, metals and drink cartons. What I found out was the majority of that PMD bag was not plastic. They even contained a lot of paper packaging such as the takeout containers from the canteen. They still had a layer of plastic on them so I get why people would be confused. But then there was the clearly recycled paper or sugarcane-based plates and the various mixed plastic items which could never properly be mechanically recycled. sigh Sorting through the waste and cleaning through all of them was extremely physically taxing. I collected 5 bags on a Tuesday at around 11am and I could I spent the rest of the time weighing them and clearing out the non-plastics. Then came the laborious task of cleaning the waste… Oooff! I had to clean the 5 bags before I got 5 more bags on Thursday… Yeah that didn’t happen.
By the third collection day, I had made a sort of assembly line of how to manage the space I had in this storage room. Luckily, it had a sink so I could weigh the plastic, wash them, dry them, and weigh them again systematically. It was definitely a mountain of work to clean up this plastic waste in the name of science. But making a system to clean and sort the waste and taking one bag at a time helped me to go through all 47 samples in 4 weeks. Doing all of this by hand helped me to value all the workers who help keep our buildings and cities clean even more. Think about it, the waste I collected was, but a fraction of the waste generated in the four buildings of my sample, let alone the entire university.
I was incredibly mortified by this experience. It taught me that the plastics problem isn’t just a “third world problem”. Bluntly put, people in my university don’t know how to segregate waste properly either. It’s not totally their fault. For the most part it’s hard to figure out where certain items go if they are made up of multiple materials or if you are not familiar with how the waste management system works. The other thing I realised is that no matter how much awareness is spread about plastic bottles and single use plastics, the sad truth is that they are too convenient to get rid of. Plastic bottles, plastic clamshell packaging and even plastic cups were quite common in the university waste. It was me having a literal “hands-on” experience of this plastic waste issue.
Once all batches were collected and cleaned. I separated the plastics based on the resin code. This is the tiny triangle you see on the plastics with the number 1-7. Side note: THIS DOES NOT SAY THAT THE PLASTIC IS RECYCLABLE. That is indeed a common misconception by many of us. It’s a trick done by the plastics companies, the recyclable symbol and this resin code looks very similar so if you don’t look carefully, you will be misled.
Now you might be wondering why I went through the trouble of collecting and cleaning plastics. The answer is simple - Utrecht University didn't have an overview of its plastic waste per type so this was one of the first studies done to fill in the research gap. I decided that taking samples was the best way to collect this data rather than using a questionnaire to estimate how much plastic waste people throw away. If I had more time, of course, I would have done three things to improve the validity of my results. 1. chose a larger sample size, 2. chose a wider range of buildings and 3, collected samples from multiple time periods of the year.
The cleaning and sorting stage is pretty important as it puts into perspective the huge challenge of waste cleaning and separation. In plastic recycling, be it mechanical or chemical, the plastics need to be clean and, in the case of mechanical recycling, need to be of a single plastic stream. This job what I did by hand, is almost completely automated and uses high-tech cameras and infrared sensors to identify the plastic type and send it to the right place. But this stage takes a lot of water, cleaning agents and electricity and is an important stage before actual recycling takes place. No wonder a lot of money needs to go into this stage no matter the recycling method you use.
Next up on Master thesis diaries - even more stumbling blocks and my experience with pyrolysis experiments and lab work 😄
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