Team:Virginia/project-description

TRANSFOAM

Team Attributions
Description Design Experiments Model Safety
Results Future Directions Demonstrate
Parts Collection
Integrated Human Practices Public Engagement Collaborations Mid-Atlantic Meetup
Awards Medals

Plastic Waste

In the last century, plastic has transformed from an unknown polymer to an essential component of the modern world. Global plastic production has dramatically risen from 50 metric tons in 1976 to 348 metric tons in 2017.1 The unprecedented accumulation of plastic developed a short-sighted waste management system with deadly consequences. 80% of plastic waste is directed to landfills which wreak havoc on the environment.2 In landfills, toxins in plastics accumulate into a harmful leachate which is dispersed into our atmosphere and water systems.3 12% of plastic waste is incinerated which release pollutants like particulate matter and sulfur that threaten environmental and human health.4 Around 10% of all plastic waste finds its way into our oceans where they break down into microplastics. When ingested by marine wildlife, microplastics dismantle marine ecosystems.5

Society clearly cannot continue its uncontrollable plastic waste generation; however, it is too reliant on plastic use. An alternative plastic which can carry out the functions of conventional products but does not introduce harm is needed.

Consequences of Polystyrene

Polystyrene, specifically expanded polystyrene (EPS), constitutes a large percentage of non-recycled plastic. Only about 12% of polystyrene is recycled, while the other 88% reaches landfills and waterways.6

Accumulation in Landfills

EPS is made up of 95% air by volume, taking up a substantial amount of space in landfills and making it both physically and economically difficult to transport and recycle.7 Thus, it is less expensive for companies to produce new polystyrene products than to recycle old ones. This illustrates the lack of a “closed-loop” system for polystyrene recycling.


Pollution Resulting from Incineration

As a result of its space-taking quality and inability to be efficiently recycled, polystyrene waste is often left to be incinerated. This thermal degradation of polystyrene in open environments introduces toxic pollutants, such as polycyclic aromatic hydrocarbons, into the atmosphere. Such compounds are known to have potential carcinogenic properties. Incineration also leads to carbon dioxide emissions, contributing to climate change and public health risks.4


Contributor to Microplastics

Polystyrene waste that is not contained in landfills and that is exposed to sunlight degrades into tiny fragments known as microplastics. In fact, approximately 80% of microplastics in the ocean originates from land-based sources. These plastic remains then pollute waterways and collect contaminants, harming marine life and destroying ecosystems. The Society of Environmental Toxicology and Chemistry highlights that the 4.793 - 12.45 million metric tons discrepancy between the volume of microplastics released into waterways and the volume that floats at sea-level is largely attributed to ingestion by marine life. This, in turn, introduces toxins to the marine food web, giving rise to human health issues.8

PHBs are the Future of Plastics

There have been many attempts to find a plausible solution to plastic waste. A forerunner in this is poly-hydroxybutyrate (PHB), a specific derivative of the group poly-hydroxyalkylates (PHAs). This biodegradable plastic has various uses from plasticware to surgical stitches. As reflected in its name, biodegradable plastics degrade back into nature, preventing accumulation in landfills and subsequent polluting risks.9 All of these benefits have encouraged scientists to efficiently develop biodegradable polymers with properties comparable petrochemical plastics. One such strategy involves feeding waste-carbon sources, such as sunflower oil, to bacteria to produce biodegradable material.10 To optimize quality, efficiency, and sustainability of biodegradable plastic production, our team had the idea to utilize E. coli and a common waste source, polystyrene, to generate PHBs.

Our Solution

Our solution tackles both ends of the plastic problem: it chemically remediates polystyrene in order to produce PHBs, a sustainable alternative to current petroleum-based plastics. Polystyrene is a usable waste product that is not being used to its potential. Rather than leaving it to negatively impact the environment, polystyrene can be utilized as a tool for a more sustainable plastics market. The specific waste product we chose for our device was styrene, the monomer of polystyrene. Polystyrene can be converted to its monomer through pyrolysis. More information about this process can be found on our Human Practices page.

The biological device contains two plasmids necessary to metabolize styrene and produce PHBs. The first plasmid contains the styABCDE gene cluster, which is capable of catabolizing the transformation of styrene to phenylacetic acid. Our chassis organism, E. coli K12 TG1, contains the paa gene cluster capable of catalyzing the conversion of phenylacetic acid to acetyl-CoA.11 This cluster is crucial to marrying the two plasmid reactions together to create one integrated device. The second plasmid catalyzes the conversion of acetyl-CoA to poly-hydroxybutyrate. This completes the overall pathway outlined in our designed chassis.

Transfoam in Society

Transfoam is not just a device. It’s a movement dedicated to resolving the plastic waste crisis. Such a multifaceted problem demands a multifaceted solution. While synthetic biology is an essential component for developing sustainable plastic technology, social engineering is also necessary to reform the infrastructures that drive unsustainable plastic consumption practices. Our human practices aimed to redesign plastic management streams through political and educational initiatives.

  1. Global plastic production. Statista https://www.statista.com/statistics/282732/global-production-of-plastics-since-1950/.
  2. Geyer, R., Jambeck, J. R. & Law, K. L. Production, use, and fate of all plastics ever made. Sci. Adv. 3, e1700782 (2017).
  3. FAQs on Plastics. Our World in Data https://ourworldindata.org/faq-on-plastics.
  4. Sharma, R., Sharma, M., Sharma, R. & Sharma, V. The impact of incinerators on human health and environment. Rev. Environ. Health 28, 67–72 (2013).
  5. How much plastic is in the ocean? | Natural History Museum. https://www.nhm.ac.uk/discover/quick-questions/how-much-plastic-is-in-the-ocean.html.
  6. US EPA, O. Plastics: Material-Specific Data. US EPA https://www.epa.gov/facts-and-figures-about-materials-waste-and-recycling/plastics-material-specific-data (2017).
  7. Horvath, J. S. Expanded Polystyrene (EPS) geofoam: An introduction to material behavior. Geotext. Geomembr. 13, 263–280 (1994).
  8. Burgess, R. M. et al. Microplastics in the aquatic environment—Perspectives on the scope of the problem. Environ. Toxicol. Chem. 36, 2259–2265 (2017).
  9. Getachew, A. & Woldesenbet, F. Production of biodegradable plastic by polyhydroxybutyrate (PHB) accumulating bacteria using low cost agricultural waste material. BMC Res. Notes 9 509 (2016).
  10. Lykidis, A. et al. The Complete Multipartite Genome Sequence of Cupriavidus necator JMP134, a Versatile Pollutant Degrader. PLOS ONE 5, e9729 (2010).
  11. Ferrández, A. et al. Catabolism of Phenylacetic Acid in Escherichia coli CHARACTERIZATION OF A NEW AEROBIC HYBRID PATHWAY. J. Biol. Chem. 273, 25974–25986 (1998).