According to Oliver Peoples, 'the most important plastic property you can have is cost’. By eliminating the expensive fermentation technology currently used to produce PHA biopolymers and turning instead to the crop-based production of these materials, he is creating PHAs with precisely that property - and opening the door for the broad adoption of these materials.
Oliver Peoples, the president and Chief Executive Officer of Yield10 Bioscience, with many decades of experience with the development and production of PHAs, knows what he is talking about.
Having previously been in the business of producing PHAs via fermentation, he knows just how important price is, and how this affects the material’s uptake by the market.
“There is a huge disconnect between market demands and market price points - and the end uses. It’s a material for the single-use market, but the cost of production is probably three to five times more expensive than petroleum plastics and that is, fundamentally, the issue,” he said.
What is PHA?
PHAs, or polyhydroxyalkanoates are a family of biopolyesters produced in nature by numerous microorganisms. They are synthesized directly via fermentation of a carbon substrate, varying from sugar and lipids to sewage, coffee grounds or methanol, inside microorganisms, and stored in the form of water insoluble granules as energy and carbon reserves inside their cells. PHAs are synthesised by microbes in nutrient-deficient conditions. They are separated from the microbes with the help of a solvent; the solvent is then removed, the harvested PHA is washed, dried and pelletised through an extruder. The pelletised PHA is ready for packaging and market sale.
Not only are PHAs derived from renewable sources, but they are also fully biodegradable – in soil and water - compostable and biocompatible. As a result of this latter property, PHAs find many applications in the medical field. Importantly, unlike most plastics, biobased or otherwise, certain PHAs will also degrade in the oceans - a property that has generated growing enthusiasm for their use, in the light of the discussions about marine plastics.
The properties of these materials – they can be thermoplastic or elastomeric - are highly ‘tuneable’: PHAs can be engineered to meet the performance requirements of a wide range of applications currently using fossil fuel-based PE, PP, PS, PET, PVC or TPU.
Their biodegradability, under aerobic and anaerobic conditions, means that one of their most established applications is flexible films for compostable waste bags or carrier bags for organic waste, and mulch films in agriculture. PHA materials are highly suitable for packaging and other single-use applications – e.g. straws, disposable cutlery and serviceware.
The most common PHA, first described by a French scientist called Lemoigne in 1925, is poly(3-hydroxybutyrate), or P3HB. Since then, many different fermentation strategies and downstream methods have been explored in a bid to establish efficient production of this bio-based polymer at scale.
One of the issues that has long hindered attempts to scale up PHA production is the cost of the carbon source metabolised by the microorganisms, which has made traditional methods for PHAs production extremely expensive. Many PHA manufacturers rely on high-cost substrates such as pure sugars, fats, and animal or vegetable protein. As a result, the cost of the carbon source can contribute to up to 60 percent of the overall cost of PHA production.
A different approach
Turning a cost-intensive process that requires significant investment in fermentation technology to convert sugars into polymer into an economically viable product has proven to be a daunting challenge.
“But what if we could bypass this inefficient and expensive process altogether? This is where Camelina, an oilseed crop that has been used for centuries, comes in,” said Peoples. When he was at MIT, he had already come up with the basic idea that it should be possible to take genetic information from any living thing and use that information with whatever it did to build production systems in other organisms.
Obviously, the genetic information in the microorganisms that enables them to ferment sugar into PHA is lacking in Camelina.
“But what if we could take this genetic information and insert it into Camelina so that it could produce PHA bioplastics directly? So that next to oil and protein, it could also produce PHAs in the seeds?” asked Peoples. The idea, he explained, came from looking at the production of starch - one of the cheapest polymers in the world - because it is made in a plant.“Sometimes you kind of just need a simple thought,” he said. “If you really want to scale from a biological production system, the best way to do that is with agriculture.”