Bio (logic)

11-02-18 Plastic trends

One of the bio-based plastics that have attracted major interest in recent years is PHA. Produced by bacteria, PHA is not just one, but a family of naturally occurring biopolyesters with the potential to replace a host of conventional, fossil-based resins.
Polyhydroxyalkanoates are a family of bio-based plastics that would seem to have everything going for them: renewably sourced, biocompatible, biodegradable and produced using carbon sources ranging from methane to sewage, although the fermentation performance by the bacteria differs according to feedstock.
Importantly, unlike most plastics, bio-based 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 polyethylene, polypropylene, polystyrene, PET, PVC or thermoplastic polyurethane. In fact, their versatility has now led the industry to refer to the PHA platform, much the same as it refers to the wide variety of nylon resins.

PHAs are synthesized by many microorganisms when in harsh conditions and in distress, as a reserve source of carbon and energy. The most common PHA, first described by French scientist Maurice 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 its efficient production.
PHA production starts with bacterial cultures, which are fed with a carbon-rich feedstock — for example, sugar or fatty acids. To extract the PHA, first the biomass is harvested from the cultures through filtration or centrifugation, after which this undergoes a pretreatment designed to make the extraction process — which occurs through chemical, mechanical, physical or biological means — easier. The solvent method is the most commonly used extraction method, although enzymatic digestion has also been employed.
Mechanical methods are also being investigated; as mechanical disruption uses no chemicals, the environmental impact is minimal (...)

Their potential for replacing fossil-based plastics has long been recognized, with initial efforts to commercialize these materials dating back to the 1980s. The problem, as is often the case with bio-based plastics, was cost. PHA could not, and still struggles to, compete with the bulk production of petrochemical plastics.

As biopolymers consultant Jan Ravenstijn pointed out last year in a presentation on the PHA platform, the market price of PHA tends to be three to four times the price of the products they are intended to replace. The simple fact that PHAs are renewably sourced and biodegradable will not create demand and "you cannot ignore the law of polymer marketing," Ravenstijn said.
"Always, price and quality come first and only when PHA fulfills the price/quality requirements of the market will customers be willing to buy it. Only then will the fact that it is biodegradable become a powerful, additional sales argument," he said.

Processability and commercialization
Price aside, Ravenstijn also mentioned a few other issues that PHA materials need to address. For example, PHAs generally have a low nucleation density and therefore slow crystallization rates, which makes them less suitable for injection molding, as this leads to long production cycle times. Research is ongoing to determine whether and which nucleating agents can be used to remedy this. Molecular chain scission occurs above 160° C and the polymer starts to degrade, which makes low-temperature processing essential.
(...)
Ravenstijn further noted that in his experience, it takes a good 20 years or more and upward of $1 billion for a new polymer to become a commercial success. Starting from scratch with a new polymer and going through the stages of development, customer acceptance and production at industrial scale is one of the hardest things to do, he said. This was the case for polylactic acid, and it is what polyethylenefuranoate, another biopolyester that is based on furanic technology and is currently produced at pilot scale by a select number of companies.

Need for value chain alliances
Right now, the PHA market, as such, is only gradually starting to take shape due to the efforts of the players in this market. Aiming to reduce production costs, major investments have been funneled into the development of efficient bacterial strains, fermentation and recovery processes.
While successes have been announced at lab and pilot scale, the step toward industrialization and commercialization continues to be difficult. (...)

(...) a company announced it entered into partnerships to create specific PHAs for electronics, food packaging, materials and cosmetics.

PHAs are slowly starting to penetrate various fields, among which packaging, medical and coating materials, and finding application in nonwovens, polymer films, sutures and pharmaceutical products, as well as low-value, high-volume products such as compost bin liners. Yet, as long as the value chain remains ignorant about just what the PHA platform is, progress will continue to be slow.

(...) : "Although manufacture with PHAs currently presents a significant process development overhead for what still seems like a very niche market, interest is continuing to grow and the rewards for early adopters could well be significant."

At the end there should be more efforts/ investments for R&D, with political support to achieve certain targets in product and time, otherwise it will be always "cosmetic affairs";