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Circe: Transforming greenhouse gases into biodegradable products

A platform that uses engineered microbes to produce synthetic polymers with minimal environmental impact

Circe: Transforming greenhouse gases into biodegradable products
The Circe project is led by Shannon Nangle, Ph.D. (left) and Marika Ziesack, Ph.D. (right), both Research Scientists at the Wyss Institute who are passionate about using microbes to solve some of the world’s most challenging problems. Credit: Wyss Institute at Harvard University

Our society is built upon cheap, widely available petrochemicals. Beyond gasoline and other fuels, petrochemicals are primary components of many of the objects in our everyday lives, including clothing, cosmetics, electronics, packaging, paint, floors, cars, and furniture. The vast majority of these products do not biodegrade in the environment and are not recycled, and the process of manufacturing them produces greenhouse gases and pollution that are damaging our shared environment. Some companies are beginning to make compostable “bioplastic” products via the fermentation of large amounts of sugar derived from plants. While a step in the right direction, sugar fermentation is not feasible on a global scale, as the land needed to produce the sugar would stress our ability to produce enough food to support our growing population.

Manufacturing a smaller carbon footprint

The Circe (Circular industries with cellular factories) Institute Project aims to address this problem by using engineered microbes to produce polymers that can be used to manufacture a wide variety of products with a smaller carbon footprint and environmental impact. Rather than using sugar from acres’ worth of crops as their food source, Circe’s proprietary microbes take in carbon dioxide (CO2) and hydrogen (H2) gases and produce a class of biodegradable fatty acid polymers called PHAs (polyhydroxyalkanoates) via gas fermentation. These polymers can then be used to make bioplastics, biodegradable polyesters, and more.

We envision a truly circular economy in which microbes convert gases to commodity products — from plastics to food to clothes, etc. — and then break them back down to simple gases to restart the cycle.

Shannon Nangle

Circe integrates this process into a platform that enables greenhouse gases created by industrial processes to be harvested and converted into valuable polymers. A carbon harvester is installed at a CO2 or methane emission source, and the carbon is combined with hydrogen, also produced on-site, to feed the microbes. After being cultured, the microbes are processed and the polymer is purified into a dry material that can be shipped, stored, and used in products that are currently made with petrochemical-derived polymers. These polymers are non-toxic and readily degrade in the oceans and on land.

Circe: Transforming greenhouse gases into biodegradable products
The engineered microbes in the Circe system take in carbon dioxide produced by the burning of fossil fuels and hydrogen gas and use them to produce a class of biodegradable fatty acid polymers. These polymers are purified and can then be used to manufacture a wide range of biodegradable products, with a much smaller environmental footprint than plant-sugar-based bioplastics. Credit: Wyss Institute at Harvard University

Biodegradable products

Like many of the things we interact with on a daily basis, the vast majority of personal care products contain ingredients that are produced from petrochemicals for a variety of purposes, including thickening and maintaining a smooth consistency. These ingredients do not biodegrade and some, like plastic microbeads, are directly contributing to the plastic pollution problem. The Circe team is working to be a part of the “clean beauty” movement by replacing these petrochemical ingredients with ingredients that are produced by its engineered microbes, in support of a fully sustainable bioeconomy. Following development and commercialization of this proof-of-concept, they plan to expand the Circe system into other products and industries, such as animal-free food products.

Potential applications

Circe has the potential to create biodegradable products with smaller carbon footprints in the following areas:

  • Personal care products
  • Single-use plastics
  • Packaging
  • Textiles
  • Footwear
  • Agriculture
  • Electronics

The Wyss Institute is currently de-risking this technology, and is seeking industrial partners to assist with commercialization and funding efforts.

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