Advanced approaches to produce polyhydroxyalkanoate (PHA) biopolyesters in a sustainable and economic fashion

Polyhydroxyalkanoates (PHA), the only group of “bioplastics” sensu stricto, are accumulated by various prokaryotes as intracellular “carbonosomes”. When exposed to exogenous stress or starvation, presence of these microbial polyoxoesters of hydroxyalkanoates assists microbes to survive.

“Bioplastics” such as PHA must be competitive with petrochemically manufactured plastics both in terms of material quality and manufacturing economics. Cost-effectiveness calculations clearly show that PHA production costs, in addition to bioreactor equipment and downstream technology, are mainly due to raw material costs. The reason for this is PHA production on an industrial scale currently relying on expensive, nutritionally relevant “1^st-generation feedstocks”, such as like glucose, starch or edible oils. As a way out, carbon-rich industrial waste streams (“2^nd-generation feedstocks”) can be used that are not in competition with the supply of food; this strategy not only reduces PHA production costs, but can also make a significant contribution to safeguarding food supplies in various disadvantaged parts of the world. This approach increases the economics of PHA production, improves the sustainability of the entire lifecycle of these materials, and makes them unassailable from an ethical perspective.

In this context, our EU-funded projects ANIMPOL and WHEYPOL, carried out by collaborative consortia of academic and industrial partners, successfully developed PHA production processes, which resort to waste streams amply available in Europe. As real 2^nd-generation feedstocks”, waste lipids and crude glycerol from animal-processing and biodiesel industry, and surplus whey from dairy and cheese making industry were used in these processes. Cost estimations made by our project partners determine PHA production prices below 3 € (WHEYPOL) and even less than 2 € (ANIMPOL), respectively, per kg; these values already reach the benchmark of economic feasibility.

The presented studies clearly show that the use of selected high-carbon waste streams of (agro)industrial origin contributes significantly to the cost-effectiveness and sustainability of PHA biopolyester production on an industrial scale.