Thinking Outside the Box: Turning Methane into Biodegradable Plastic
By building a closed-loop system, Mango Materials tackles two environmental problems: climate change and plastic pollution
After completing her Ph.D. in Civil & Environmental Engineering in 2009 at Stanford University, Molly Morse harnessed her research on the production of PHA (polyhydroxy alkanoate) biopolymers from methane — and its biodegradation — and shaped it into a start-up business in 2010. Where her research at Stanford laid the theoretical groundwork, Mango Materials would focus on commercialization. “You know you have something worth commercializing if people do indeed want to buy it,” Molly said. After talking to customers, brands, and other interested parties, Molly and her three co-founders, Allison Pieja, Anne Schauer-Gimenez, and Bill Shelander, discovered their niche.
Since we can’t just recycle our way out of the plastic pollution problem, there would need to be a number of biodegradable solutions instead. Mango Materials’ founders participated in an accelerator, Cleantech Open, where they learned about business plans, financial modeling, logo making, and how to incorporate. And with the help of a Phase 1 National Science Foundation grant, they were able to access other investment opportunities. But the road wasn’t always easy.
“Some of the greatest challenges we faced early on have been access to funding,” Molly admitted. “We’re a start-up company and we’re located in the San Francisco Bay area, but this is a capital-intensive endeavor. We need pumps and tanks, and we do advanced biotechnology. It takes a while to build these sorts of companies. Access to capital for something like this is… It’s tricky to find the correct match.”
That said, Molly is grateful for the variety of funders that have gotten Mango Materials to where they are now. And it remains an uphill battle because, “well, we’re competing against conventional plastics,” Molly said. “These are materials that are produced at very high volumes and at very low cost — and they have amazing properties.”
“We need to scale up the production of biodegradable and rapidly renewable materials — not just Mango Materials, but others as well — to be able to compete on price. That is the key challenge that the whole industry faces.”
Working at a start-up, Molly said, “is not for the faint of heart.” “There’s a lot of uncertainty and ambiguity that goes along with not only running a start-up company but working at one.” Yet the adventure excites her. So does the potential of making PHAs a household name.
What are PHAs?
The most common biopolymer (or material made from biomass) that people are familiar with is PLA, polylactic acid. Its versatile, degrades, and can be used to make films, bottles, and other final products. The ones Mango Materials works with, polyhydroxy alkanoates, or PHAs, are a family of naturally occurring bio-polyesters with different heat and moisture properties. While they’ve been known for a century, they haven’t been widely commercialized.
“Many living things on planet earth produce different forms of PHAs, including PHB, poly 3-hydroxybutyrate, which is the type of PHA Mango Materials produces.” This is done through bacteria. Normally, Molly explained, bacteria will produce a couple percent of PHA by cell weight. What Mango Materials does is control conditions in such a way that the bacteria yields very high levels of it. “You essentially do this by triggering the bacteria to think a famine’s coming,” she said. “So instead of using the carbon that you feed the bacteria to reproduce, they store it inside their cell walls.”
This is accomplished by feeding different types of bacteria different types of carbon, most often sugar. “You take sugar, feed that sugar to bacteria, and the bacteria produce the PHA inside their cell walls which you then harvest and use as a plastic replacement.” For the most part, though, Mango Materials uses methane gas instead. “We can use many forms of methane because methane is the key component in natural gas, but it’s also produced from waste processes like wastewater treatment plants, landfills, agricultural facilities, and abandoned coal mines,” Molly said. “So we can use this waste methane, which is a potent greenhouse gas, to feed the bacteria to produce PHA. That’s what makes Mango Materials unique.”
“One of the core focuses is on using this waste methane feedstock to make PHA.”
Ultimately, Mango Materials hopes its PHA can serve to replace everyday conventional plastics. “We can formulate the P3HB for very specific applications,” Molly explained. “You can make polyethylene into lots of different forms: you can mold it, you can extrude it into a fiber. PHA is the same way.”
The company’s YOPP PHA Pellets (the YOPP standing for “You Oust Polluting Plastics”) can be formulated into injection molding, which is well-suited for products like caps and bottles, fibers, which can be an alternative to polyester found in apparel and upholstery, 3D printing, to rapidly print rigid objects, and films, for difficult-to-recycle flexible packaging.
“And we can make sure the formulation is just so, so that the material can still be susceptible to enzymatic attack when it’s no longer needed. That means it’s still biodegradable,” Molly added. “Being able to formulate the PHA so that it has the best melt properties and mechanical properties, coupled with the biodegradability properties, that’s a unique technical knowledge that Mango Materials has.”
What biodegradable really means
“There are a lot of different words that are thrown out there: biodegradable, bio-based, biopolymer, bioplastic,” Molly said. “Biobased” boils down to where the carbon comes from — whether it’s a rapidly renewable carbon or ancient fossil fuels — but that’s not the same as whether a material is actually biodegradable. Most materials break down eventually — even if it’s 2% over 300 years, Molly explained — which is where the confusion about biodegradability stems from. The crucial question is: Is a polymer prone to enzymatic attack when it’s no longer needed? Can it be fully digested until its end carbon elements (CO2, CH4)? According to Molly, you want the material to reach its end carbon elements to make sure it doesn’t persist in nature.
“[Some people] think just because it’s made from plants, that means that it will biodegrade or it won’t pollute the oceans. But you can make PET, which is pretty darn resistant, out of sugar cane or another rapidly renewable carbon.” At the end of the day, there is no silver bullet. Fixing one part of the problem won’t solve our pollution problems. Molly, and Mango Materials, are in it for the long game.
“We plan to scale up. This is a problem we want to solve. We would one day like to be a household name, in terms of PHA being a solution,” Molly said. “Picture PET, or the different brand-named polymers, like Lycra or Spandex, that people know of. We would like to be a household name like that, where we are actually creating a movement and allowing customers to vote with their dollars when they choose the material that their product is made out of.”
“We are addressing two environmental problems: One, that of waste methane — what are you going to do with it? And two, the persistent pollution of plastics, when they’re improperly disposed of or when they’re no longer needed.”
Change, or as Molly calls it, a movement, starts at home — with me, and with you. “Yes, I’m in the business of making materials and would want customers ultimately to choose our material,” Molly said. “However, if you don’t need something or you can use something that’s reusable, that should be what you do first. We should use less stuff in general. And if we do need single-use items, then great — let’s make them biodegradable.”
Want to learn more? Molly Morse recommends watching The Story of Plastic, a documentary about the complex, widespread issue of pollution plastics, and what companies like Mango Materials are doing to combat the issue.
