Yuting Ji, Pachara Lobunchongsook, Ethan Markey, Umamah Mokarram, Terry Wong, Lauren Young and Ella Zhou
- Degree: Bachelor of Applied Science
- Program:
- Campus: Vancouver
Our project
Plastics are a problem. At the end of their life – which for many plastics is only a one-time use – the majority of plastics are landfilled or discarded, where they break down into harmful microplastics that pervade our ecosystems and bioaccumulate in food chains. To address this issue, we developed a process and designed a theoretical plant to develop polybutylene succinate (PBS), a biodegradable bioplastic that quickly and naturally breaks down into water and carbon dioxide.
Our process and design solution
We developed a five-stage process that takes raw chemicals and transforms them into PBS granules, which could then undergo further processing or post-treatment steps to be used in a wide variety of plastics applications in place of PET or other plastics made from petrochemicals.
We begin with an esterification process that combines succinic acid and methanol to produce dimethyl succinate (DMS). The next stage separates out DMS and methanol (which is saved for reuse). Butanediol and DMS are combined in a transesterification reaction to produce PBS oligomers and methanol. The methanol and butanediol are then separated for reuse, and the PBS undergoes a polycondensation reaction, where PBS oligomers attach to form long chain lengths to become PBS polymers. The final polymers are granulated to produce PBS granules.
To encourage circular economy, we have sourced reactants that are produced sustainably. While succinic acid is traditionally produced through petrochemical pathways, our plant sources succinic acid produced through a fermentation process from the breakdown of biodegradable waste, which in our case is corn. Butanediol is another reactant that can be produced in a similar manner (e.g., from corn and/or other plant sugars).
However, finding sustainable sources for our third reactant, methanol, was more of a challenge. Green methanol production requires significant amounts of renewable energy inputs at great costs. Currently there is no way to produce green methanol outside of lab or pilot-scale operations.
To ensure our plant is cost-effective, we are using traditionally produced methanol, but we have designed our process to recycle methanol as much as possible (at a 10:1 ratio) to minimize our need to purchase methanol.
We designed a general plant layout and have proposed siting our plant near Chicago, Illinois, to take advantage of proximity to a major producer of succinic acid. We also developed an economic assessment of the project, which forecasts revenue of just over $43 million annually. Our operational expenses are predominantly made up of our raw materials, and our operations are particularly sensitive to the price of biobased succinic acid.
The challenges we faced
As chemical engineering students, we are system thinkers who look at big processes and consider the lifecycle of real-world problems that need to be addressed from start to finish.
That means we consider everything from where the plant is located and its energy and materials requirements to the biodegradability of our product and the policies that must be in place to implement this process in profitable and beneficial ways. It can be a challenge to tie everything together.
Our project is a theoretical process and plant design based on our research. We know we have the correct reactions, conditions and catalysts, but we don’t know the specific optimal parameters of our process. To gain this understanding, we would need to conduct lab-scale experiments and then scale them up to see how they perform in a commercial capacity.
Our project is also limited by the current state of knowledge of PBS’s biodegradability. Our research suggests that under optimal conditions (high temperatures, high moisture content and high microbial activity) PBS plastic in a natural environment could biodegrade in a six-month to five-year period, and in an industrial composting facility it could biodegrade as quickly as in a few weeks. However, as a baseline plastic, PBS would need to undergo further treatment or processing for its end application, which could decrease its biodegradability.
Our project’s future
While research into biodegradable bioplastics has become increasingly popular, further research is still required and industry still faces issues implementing these products on a larger scale.
There is an incredible opportunity to expand the research and market of bioplastics, given how reliant we are on plastics for their versatility and the profound environmental harms that come from traditionally made plastics.
Could there be a time in Canada and the world when, rather than PET plastics, the plastic market is dominated completely by bioplastics? The process and plant design we’ve proposed could also be very valuable in countries that currently have less infrastructure in place to support plastics recycling. Our product could biodegrade in just a few months, without leaching microplastics or harmful chemicals into the land or water.
