PHA: it’s in the genes

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.”

This is precisely what the team of scientists at Yield10 Bioscience have been working on. Founded in 2017, the company has continued the work of its predecessor company, Metabolix. While Metabolix was a pioneer in the development of advanced PHA bioplastics production technology using engineered microbes and fermentation, the company also ran a crop science research programme to produce PHA biomaterials in crops as a potential low-cost production system. Now, using genetic modification technology, the researchers at Yield10 Bioscience have successfully created a plant that can do precisely that – and more. Their Camelina plant produces three different products: oil, protein and PHA.
“We have taken the genetic information that's missing from the plant - in this case Camelina - from a microorganism; we’ve have reprogrammed it and we've inserted into the plant. And now that plant can take sunlight and CO2 and make PHA.”
The implications of this breakthrough are massive. “Suddenly we don't need hundreds of millions of dollars of capital to build a fermentation facility and we don't need three or four pounds of sugar to make a pound of PHA. The result is a three-component seed product that includes vegetable oil, protein and PHA bioplastics, all produced by the same plant. Vegetable oil today is in enormous demand for decarbonising aviation fuel while protein is used for animal feed. So, we have three separate industrial products from the one seed.”
This has a massive impact on the capital costs of producing the materials, Peoples continued.  “And on the operating cost, as it brings this down to the level of traditional chemical materials. The third thing it does is it enables very large scale, which is essential for the widespread adoption of bioplastics in the industry.”
The ability to optimise the economics of any one product by leveraging the value of the others is similar to how the petroleum industry works, but with the added benefit of producing environmentally friendly materials.
Asked about the yield – in terms of pounds of PHA - that is possible to get from a plant, a quick estimate would be between 200 and 500 pounds per acre, Peoples said.
“The way to think about it is, on an acre of land, if you're producing say 2000 pounds of seed and 20% of that was basically PHA - 400 pounds of PHA -  and then it just scales from there. But because you have two other products coming from that plant at the very same time, it's a very high value crop. And how do you incentivise farmers and land owners? By making something profitable for them. This crop offers a compelling value proposition for growers, a clear economic return, year on year.”
He said there was no reason why 50,000 acres could not be grown in North America alone, resulting in ‘a whole different equation from fermentation’, and consequently bringing the price of the biopolymer down considerably. As the plant makes the finished polymer, the company must simply extract the finished polymer from the seed and ship it to compounders to make plastic pellets for the commercial market.
“In terms of the economics of the situation, this is like having a refinery that makes free products,” he said.

What’s next?
“We have what we believe will be disruptive technology in the bioplastics space,” emphasised Peoples. “I would say that two-and-a-half years ago, the company took a big step - once we found the new approach to the bioplastic and Camelina, what we did was to shift the company's focus to commercialising Camelina. It was for us a big transition from an R&D focus to a commercial focus.”
However, Yield10 is not yet selling PHA commercially. “We're basically still developing it - this is the challenge, and it takes time.  Basically, we've scaled it up. We've been doing hectare-scale field trials and we are planning to continue to expand the programme,” said Peoples. This includes developing PHA winter Camelina lines – we are doing this in Saskatchewan - and advancing the research programme to increase the level and type of PHA production achievable in the Camelina plant varieties. The current focus is on boosting the level of PHA in the seed of Camelina to the targeted 20 %. As well, the company is working to create PHA pathways that enable the production of PHA co-polymers in Camelina. 
Asked about the volumes Yield10 expects, he said that initially probably something in the neighbourhood of 100 million pounds would be feasible. He expected this would rapidly increase to around two million tons, ‘at which point it starts to get interesting’, he added.
After all, it is a natural product, and the demand is there. Not calling it plastic will also boost its acceptance as a material.

However, one of the main uses will be in water treatment, Peoples predicted. PHAs can be used as a carbon source to remove nitrogen compounds, for example from aquaculture systems. “Or in ponds and lakes, where there is algae overgrowth because of nitrogen pollution. Adding PHA can solve the problem,” he said. “And of course, it's a natural thing, so there's zero waste – no need to do anything afterwards. You simply drop it in and leave it  - which is surely the perfect human solution for everything.”
Meanwhile, however, Yield 10 has targeted its efforts on building its commercial capabilities and readying the product for the market. “We are busy building up an operation, launching Camelina as a platform crop, working to contract farmers and all that this involves. It is nice to be working on making a product everybody wants. And one that does some good. Making a product that people value is crucial – if you get that right, in my view, the rest will take care of itself,” he concluded.